Граф коммитов

3718 Коммитов

Автор SHA1 Сообщение Дата
Hao Jia 2679a83731 sched/core: Avoid obvious double update_rq_clock warning
When we use raw_spin_rq_lock() to acquire the rq lock and have to
update the rq clock while holding the lock, the kernel may issue
a WARN_DOUBLE_CLOCK warning.

Since we directly use raw_spin_rq_lock() to acquire rq lock instead of
rq_lock(), there is no corresponding change to rq->clock_update_flags.
In particular, we have obtained the rq lock of other CPUs, the
rq->clock_update_flags of this CPU may be RQCF_UPDATED at this time, and
then calling update_rq_clock() will trigger the WARN_DOUBLE_CLOCK warning.

So we need to clear RQCF_UPDATED of rq->clock_update_flags to avoid
the WARN_DOUBLE_CLOCK warning.

For the sched_rt_period_timer() and migrate_task_rq_dl() cases
we simply replace raw_spin_rq_lock()/raw_spin_rq_unlock() with
rq_lock()/rq_unlock().

For the {pull,push}_{rt,dl}_task() cases, we add the
double_rq_clock_clear_update() function to clear RQCF_UPDATED of
rq->clock_update_flags, and call double_rq_clock_clear_update()
before double_lock_balance()/double_rq_lock() returns to avoid the
WARN_DOUBLE_CLOCK warning.

Some call trace reports:
Call Trace 1:
 <IRQ>
 sched_rt_period_timer+0x10f/0x3a0
 ? enqueue_top_rt_rq+0x110/0x110
 __hrtimer_run_queues+0x1a9/0x490
 hrtimer_interrupt+0x10b/0x240
 __sysvec_apic_timer_interrupt+0x8a/0x250
 sysvec_apic_timer_interrupt+0x9a/0xd0
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x12/0x20

Call Trace 2:
 <TASK>
 activate_task+0x8b/0x110
 push_rt_task.part.108+0x241/0x2c0
 push_rt_tasks+0x15/0x30
 finish_task_switch+0xaa/0x2e0
 ? __switch_to+0x134/0x420
 __schedule+0x343/0x8e0
 ? hrtimer_start_range_ns+0x101/0x340
 schedule+0x4e/0xb0
 do_nanosleep+0x8e/0x160
 hrtimer_nanosleep+0x89/0x120
 ? hrtimer_init_sleeper+0x90/0x90
 __x64_sys_nanosleep+0x96/0xd0
 do_syscall_64+0x34/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Call Trace 3:
 <TASK>
 deactivate_task+0x93/0xe0
 pull_rt_task+0x33e/0x400
 balance_rt+0x7e/0x90
 __schedule+0x62f/0x8e0
 do_task_dead+0x3f/0x50
 do_exit+0x7b8/0xbb0
 do_group_exit+0x2d/0x90
 get_signal+0x9df/0x9e0
 ? preempt_count_add+0x56/0xa0
 ? __remove_hrtimer+0x35/0x70
 arch_do_signal_or_restart+0x36/0x720
 ? nanosleep_copyout+0x39/0x50
 ? do_nanosleep+0x131/0x160
 ? audit_filter_inodes+0xf5/0x120
 exit_to_user_mode_prepare+0x10f/0x1e0
 syscall_exit_to_user_mode+0x17/0x30
 do_syscall_64+0x40/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Call Trace 4:
 update_rq_clock+0x128/0x1a0
 migrate_task_rq_dl+0xec/0x310
 set_task_cpu+0x84/0x1e4
 try_to_wake_up+0x1d8/0x5c0
 wake_up_process+0x1c/0x30
 hrtimer_wakeup+0x24/0x3c
 __hrtimer_run_queues+0x114/0x270
 hrtimer_interrupt+0xe8/0x244
 arch_timer_handler_phys+0x30/0x50
 handle_percpu_devid_irq+0x88/0x140
 generic_handle_domain_irq+0x40/0x60
 gic_handle_irq+0x48/0xe0
 call_on_irq_stack+0x2c/0x60
 do_interrupt_handler+0x80/0x84

Steps to reproduce:
1. Enable CONFIG_SCHED_DEBUG when compiling the kernel
2. echo 1 > /sys/kernel/debug/clear_warn_once
   echo "WARN_DOUBLE_CLOCK" > /sys/kernel/debug/sched/features
   echo "NO_RT_PUSH_IPI" > /sys/kernel/debug/sched/features
3. Run some rt/dl tasks that periodically work and sleep, e.g.
Create 2*n rt or dl (90% running) tasks via rt-app (on a system
with n CPUs), and Dietmar Eggemann reports Call Trace 4 when running
on PREEMPT_RT kernel.

Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20220430085843.62939-2-jiahao.os@bytedance.com
2022-05-11 16:27:11 +02:00
YueHaibing 494dcdf46e sched: Fix build warning without CONFIG_SYSCTL
IF CONFIG_SYSCTL is n, build warn:

kernel/sched/core.c:1782:12: warning: ‘sysctl_sched_uclamp_handler’ defined but not used [-Wunused-function]
 static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~

sysctl_sched_uclamp_handler() is used while CONFIG_SYSCTL enabled,
wrap all related code with CONFIG_SYSCTL to fix this.

Fixes: 3267e0156c ("sched: Move uclamp_util sysctls to core.c")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-05-09 16:54:57 -07:00
Ingo Molnar d70522fc54 Linux 5.18-rc5
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 J3+wdek=
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Merge tag 'v5.18-rc5' into sched/core to pull in fixes & to resolve a conflict

 - sched/core is on a pretty old -rc1 base - refresh it to include recent fixes.
 - this also allows up to resolve a (trivial) .mailmap conflict

Conflicts:
	.mailmap

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-05-06 10:21:46 +02:00
Thomas Gleixner 16bf5a5e1e smp: Rename flush_smp_call_function_from_idle()
This is invoked from the stopper thread too, which is definitely not idle.
Rename it to flush_smp_call_function_queue() and fixup the callers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220413133024.305001096@linutronix.de
2022-05-01 10:03:43 +02:00
Thomas Gleixner d664e39912 sched: Fix missing prototype warnings
A W=1 build emits more than a dozen missing prototype warnings related to
scheduler and scheduler specific includes.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220413133024.249118058@linutronix.de
2022-05-01 10:03:43 +02:00
Dietmar Eggemann 97956dd278 sched/fair: Remove cfs_rq_tg_path()
cfs_rq_tg_path() is used by a tracepoint-to traceevent (tp-2-te)
converter to format the path of a taskgroup or autogroup respectively.
It doesn't have any in-kernel users after the removal of the
sched_trace_cfs_rq_path() helper function.

cfs_rq_tg_path() can be coded in a tp-2-te converter.

Remove it from kernel/sched/fair.c.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220428144338.479094-3-qais.yousef@arm.com
2022-04-29 11:06:29 +02:00
Dietmar Eggemann 50e7b416d2 sched/fair: Remove sched_trace_*() helper functions
We no longer need them as we can use DWARF debug info or BTF + pahole to
re-generate the required structs to compile against them for a given
kernel.

This moves the burden of maintaining these helper functions to the
module.

	https://github.com/qais-yousef/sched_tp

Note that pahole v1.15 is required at least for using DWARF. And for BTF
v1.23 which is not yet released will be required. There's alignment
problem that will lead to crashes in earlier versions when used with
BTF.

We should have enough infrastructure to make these helper functions now
obsolete, so remove them.

[Rewrote commit message to reflect the new alternative]
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220428144338.479094-2-qais.yousef@arm.com
2022-04-29 11:06:29 +02:00
Dietmar Eggemann 4e3c7d338a sched/fair: Refactor cpu_util_without()
Except the 'task has no contribution or is new' condition at the
beginning of cpu_util_without(), which it shares with the load and
runnable counterpart functions, a cpu_util_next(..., dst_cpu = -1)
call can replace the rest of it.

The UTIL_EST specific check that task util_est has to be subtracted
from the CPU one in case of an enqueued (or current (to cater for the
wakeup - lb race)) task has to be moved to cpu_util_next().
This was initially introduced by commit c469933e77
("sched/fair: Fix cpu_util_wake() for 'execl' type workloads").
UnixBench's `execl` throughput tests were run on the dual socket 40
CPUs Intel E5-2690 v2 to make sure it doesn't regress again.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20220318163656.954440-1-dietmar.eggemann@arm.com
2022-04-29 11:06:29 +02:00
Tao Zhou a658353167 sched/fair: Revise comment about lb decision matrix
If busiest group type is group_misfit_task, the local
group type must be group_has_spare according to below
code in update_sd_pick_busiest():

  if (sgs->group_type == group_misfit_task &&
      (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
       sds->local_stat.group_type != group_has_spare))
	   return false;

group type imbalanced and overloaded and fully_busy are filtered in here.
misfit and asym are filtered before in update_sg_lb_stats().
So, change the decision matrix to:

  busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
  has_spare        nr_idle   balanced   N/A    N/A  balanced   balanced
  fully_busy       nr_idle   nr_idle    N/A    N/A  balanced   balanced
  misfit_task      force     N/A        N/A    N/A  *N/A*      *N/A*
  asym_packing     force     force      N/A    N/A  force      force
  imbalanced       force     force      N/A    N/A  force      force
  overloaded       force     force      N/A    N/A  force      avg_load

Fixes: 0b0695f2b3 ("sched/fair: Rework load_balance()")
Signed-off-by: Tao Zhou <tao.zhou@linux.dev>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20220415095505.7765-1-tao.zhou@linux.dev
2022-04-22 12:14:08 +02:00
Chengming Zhou 890d550d7d sched/psi: report zeroes for CPU full at the system level
Martin find it confusing when look at the /proc/pressure/cpu output,
and found no hint about that CPU "full" line in psi Documentation.

% cat /proc/pressure/cpu
some avg10=0.92 avg60=0.91 avg300=0.73 total=933490489
full avg10=0.22 avg60=0.23 avg300=0.16 total=358783277

The PSI_CPU_FULL state is introduced by commit e7fcd76228
("psi: Add PSI_CPU_FULL state"), which mainly for cgroup level,
but also counted at the system level as a side effect.

Naturally, the FULL state doesn't exist for the CPU resource at
the system level. These "full" numbers can come from CPU idle
schedule latency. For example, t1 is the time when task wakeup
on an idle CPU, t2 is the time when CPU pick and switch to it.
The delta of (t2 - t1) will be in CPU_FULL state.

Another case all processes can be stalled is when all cgroups
have been throttled at the same time, which unlikely to happen.

Anyway, CPU_FULL metric is meaningless and confusing at the
system level. So this patch will report zeroes for CPU full
at the system level, and update psi Documentation accordingly.

Fixes: e7fcd76228 ("psi: Add PSI_CPU_FULL state")
Reported-by: Martin Steigerwald <Martin.Steigerwald@proact.de>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220408121914.82855-1-zhouchengming@bytedance.com
2022-04-22 12:14:08 +02:00
Chengming Zhou 0a00a35464 sched/fair: Delete useless condition in tg_unthrottle_up()
We have tested cfs_rq->load.weight in cfs_rq_is_decayed(),
the first condition "!cfs_rq_is_decayed(cfs_rq)" is enough
to cover the second condition "cfs_rq->nr_running".

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20220408115309.81603-2-zhouchengming@bytedance.com
2022-04-22 12:14:07 +02:00
Chengming Zhou 64eaf50731 sched/fair: Fix cfs_rq_clock_pelt() for throttled cfs_rq
Since commit 2312729688 ("sched/fair: Update scale invariance of PELT")
change to use rq_clock_pelt() instead of rq_clock_task(), we should also
use rq_clock_pelt() for throttled_clock_task_time and throttled_clock_task
accounting to get correct cfs_rq_clock_pelt() of throttled cfs_rq. And
rename throttled_clock_task(_time) to be clock_pelt rather than clock_task.

Fixes: 2312729688 ("sched/fair: Update scale invariance of PELT")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20220408115309.81603-1-zhouchengming@bytedance.com
2022-04-22 12:14:07 +02:00
zgpeng 0635490078 sched/fair: Move calculate of avg_load to a better location
In calculate_imbalance function, when the value of local->avg_load is
greater than or equal to busiest->avg_load, the calculated sds->avg_load is
not used. So this calculation can be placed in a more appropriate position.

Signed-off-by: zgpeng <zgpeng@tencent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Samuel Liao <samuelliao@tencent.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/1649239025-10010-1-git-send-email-zgpeng@tencent.com
2022-04-22 12:14:07 +02:00
Hailong Liu 915a087e4c psi: Fix trigger being fired unexpectedly at initial
When a trigger being created, its win.start_value and win.start_time are
reset to zero. If group->total[PSI_POLL][t->state] has accumulated before,
this trigger will be fired unexpectedly in the next period, even if its
growth time does not reach its threshold.

So set the window of the new trigger to the current state value.

Signed-off-by: Hailong Liu <liuhailong@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Link: https://lore.kernel.org/r/1648789811-3788971-1-git-send-email-liuhailong@linux.alibaba.com
2022-04-22 12:14:06 +02:00
kuyo chang 40f5aa4c5e sched/pelt: Fix attach_entity_load_avg() corner case
The warning in cfs_rq_is_decayed() triggered:

    SCHED_WARN_ON(cfs_rq->avg.load_avg ||
		  cfs_rq->avg.util_avg ||
		  cfs_rq->avg.runnable_avg)

There exists a corner case in attach_entity_load_avg() which will
cause load_sum to be zero while load_avg will not be.

Consider se_weight is 88761 as per the sched_prio_to_weight[] table.
Further assume the get_pelt_divider() is 47742, this gives:
se->avg.load_avg is 1.

However, calculating load_sum:

  se->avg.load_sum = div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
  se->avg.load_sum = 1*47742/88761 = 0.

Then enqueue_load_avg() adds this to the cfs_rq totals:

  cfs_rq->avg.load_avg += se->avg.load_avg;
  cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;

Resulting in load_avg being 1 with load_sum is 0, which will trigger
the WARN.

Fixes: f207934fb7 ("sched/fair: Align PELT windows between cfs_rq and its se")
Signed-off-by: kuyo chang <kuyo.chang@mediatek.com>
[peterz: massage changelog]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20220414090229.342-1-kuyo.chang@mediatek.com
2022-04-19 21:15:41 +02:00
Zhen Ni 8a0441415b sched: Move energy_aware sysctls to topology.c
move energy_aware sysctls to topology.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:44 -07:00
Zhen Ni d4ae80ffa6 sched: Move cfs_bandwidth_slice sysctls to fair.c
move cfs_bandwidth_slice sysctls to fair.c and use the
new register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni 3267e0156c sched: Move uclamp_util sysctls to core.c
move uclamp_util sysctls to core.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Baisong Zhong 28f152cd09 sched/rt: fix build error when CONFIG_SYSCTL is disable
Avoid random build errors which do not select
CONFIG_SYSCTL by depending on it in Kconfig.

This fixes the following warning:

In file included from kernel/sched/build_policy.c:43:
At top level:
kernel/sched/rt.c:3017:12: error: ‘sched_rr_handler’ defined but not used [-Werror=unused-function]
 3017 | static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
      |            ^~~~~~~~~~~~~~~~
kernel/sched/rt.c:2978:12: error: ‘sched_rt_handler’ defined but not used [-Werror=unused-function]
 2978 | static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
      |            ^~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[2]: *** [scripts/Makefile.build:310: kernel/sched/build_policy.o] Error 1
make[1]: *** [scripts/Makefile.build:638: kernel/sched] Error 2
make[1]: *** Waiting for unfinished jobs....

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Baisong Zhong <zhongbaisong@huawei.com>
[mcgrof: small build fix, we need sched_rt_can_attach() even
 when CONFIG_SYSCTL is disabled]
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni dafd7a9dad sched: Move rr_timeslice sysctls to rt.c
move rr_timeslice sysctls to rt.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni 84227c1288 sched: Move deadline_period sysctls to deadline.c
move deadline_period sysctls to deadline.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni d9ab0e63fa sched: Move rt_period/runtime sysctls to rt.c
move rt_period/runtime sysctls to rt.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni f5ef06d58b sched: Move schedstats sysctls to core.c
move schedstats sysctls to core.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni a60707d74b sched: Move child_runs_first sysctls to fair.c
move child_runs_first sysctls to fair.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Valentin Schneider cfe43f478b preempt/dynamic: Introduce preemption model accessors
CONFIG_PREEMPT{_NONE, _VOLUNTARY} designate either:
o The build-time preemption model when !PREEMPT_DYNAMIC
o The default boot-time preemption model when PREEMPT_DYNAMIC

IOW, using those on PREEMPT_DYNAMIC kernels is meaningless - the actual
model could have been set to something else by the "preempt=foo" cmdline
parameter. Same problem applies to CONFIG_PREEMPTION.

Introduce a set of helpers to determine the actual preemption model used by
the live kernel.

Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20211112185203.280040-3-valentin.schneider@arm.com
2022-04-05 10:24:42 +02:00
Nick Desaulniers 8b023accc8 lockdep: Fix -Wunused-parameter for _THIS_IP_
While looking into a bug related to the compiler's handling of addresses
of labels, I noticed some uses of _THIS_IP_ seemed unused in lockdep.
Drive by cleanup.

-Wunused-parameter:
kernel/locking/lockdep.c:1383:22: warning: unused parameter 'ip'
kernel/locking/lockdep.c:4246:48: warning: unused parameter 'ip'
kernel/locking/lockdep.c:4844:19: warning: unused parameter 'ip'

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20220314221909.2027027-1-ndesaulniers@google.com
2022-04-05 10:24:34 +02:00
Sebastian Andrzej Siewior 386ef214c3 sched: Teach the forced-newidle balancer about CPU affinity limitation.
try_steal_cookie() looks at task_struct::cpus_mask to decide if the
task could be moved to `this' CPU. It ignores that the task might be in
a migration disabled section while not on the CPU. In this case the task
must not be moved otherwise per-CPU assumption are broken.

Use is_cpu_allowed(), as suggested by Peter Zijlstra, to decide if the a
task can be moved.

Fixes: d2dfa17bc7 ("sched: Trivial forced-newidle balancer")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YjNK9El+3fzGmswf@linutronix.de
2022-04-05 09:59:36 +02:00
Peter Zijlstra 5b6547ed97 sched/core: Fix forceidle balancing
Steve reported that ChromeOS encounters the forceidle balancer being
ran from rt_mutex_setprio()'s balance_callback() invocation and
explodes.

Now, the forceidle balancer gets queued every time the idle task gets
selected, set_next_task(), which is strictly too often.
rt_mutex_setprio() also uses set_next_task() in the 'change' pattern:

	queued = task_on_rq_queued(p); /* p->on_rq == TASK_ON_RQ_QUEUED */
	running = task_current(rq, p); /* rq->curr == p */

	if (queued)
		dequeue_task(...);
	if (running)
		put_prev_task(...);

	/* change task properties */

	if (queued)
		enqueue_task(...);
	if (running)
		set_next_task(...);

However, rt_mutex_setprio() will explicitly not run this pattern on
the idle task (since priority boosting the idle task is quite insane).
Most other 'change' pattern users are pidhash based and would also not
apply to idle.

Also, the change pattern doesn't contain a __balance_callback()
invocation and hence we could have an out-of-band balance-callback,
which *should* trigger the WARN in rq_pin_lock() (which guards against
this exact anti-pattern).

So while none of that explains how this happens, it does indicate that
having it in set_next_task() might not be the most robust option.

Instead, explicitly queue the forceidle balancer from pick_next_task()
when it does indeed result in forceidle selection. Having it here,
ensures it can only be triggered under the __schedule() rq->lock
instance, and hence must be ran from that context.

This also happens to clean up the code a little, so win-win.

Fixes: d2dfa17bc7 ("sched: Trivial forced-newidle balancer")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: T.J. Alumbaugh <talumbau@chromium.org>
Link: https://lkml.kernel.org/r/20220330160535.GN8939@worktop.programming.kicks-ass.net
2022-04-05 09:59:36 +02:00
Linus Torvalds 1930a6e739 ptrace: Cleanups for v5.18
This set of changes removes tracehook.h, moves modification of all of
 the ptrace fields inside of siglock to remove races, adds a missing
 permission check to ptrace.c
 
 The removal of tracehook.h is quite significant as it has been a major
 source of confusion in recent years.  Much of that confusion was
 around task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled
 making the semantics clearer).
 
 For people who don't know tracehook.h is a vestiage of an attempt to
 implement uprobes like functionality that was never fully merged, and
 was later superseeded by uprobes when uprobes was merged.  For many
 years now we have been removing what tracehook functionaly a little
 bit at a time.  To the point where now anything left in tracehook.h is
 some weird strange thing that is difficult to understand.
 
 Eric W. Biederman (15):
       ptrace: Move ptrace_report_syscall into ptrace.h
       ptrace/arm: Rename tracehook_report_syscall report_syscall
       ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
       ptrace: Remove arch_syscall_{enter,exit}_tracehook
       ptrace: Remove tracehook_signal_handler
       task_work: Remove unnecessary include from posix_timers.h
       task_work: Introduce task_work_pending
       task_work: Call tracehook_notify_signal from get_signal on all architectures
       task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
       signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
       resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
       resume_user_mode: Move to resume_user_mode.h
       tracehook: Remove tracehook.h
       ptrace: Move setting/clearing ptrace_message into ptrace_stop
       ptrace: Return the signal to continue with from ptrace_stop
 
 Jann Horn (1):
       ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
 
 Yang Li (1):
       ptrace: Remove duplicated include in ptrace.c
 
  MAINTAINERS                          |   1 -
  arch/Kconfig                         |   5 +-
  arch/alpha/kernel/ptrace.c           |   5 +-
  arch/alpha/kernel/signal.c           |   4 +-
  arch/arc/kernel/ptrace.c             |   5 +-
  arch/arc/kernel/signal.c             |   4 +-
  arch/arm/kernel/ptrace.c             |  12 +-
  arch/arm/kernel/signal.c             |   4 +-
  arch/arm64/kernel/ptrace.c           |  14 +--
  arch/arm64/kernel/signal.c           |   4 +-
  arch/csky/kernel/ptrace.c            |   5 +-
  arch/csky/kernel/signal.c            |   4 +-
  arch/h8300/kernel/ptrace.c           |   5 +-
  arch/h8300/kernel/signal.c           |   4 +-
  arch/hexagon/kernel/process.c        |   4 +-
  arch/hexagon/kernel/signal.c         |   1 -
  arch/hexagon/kernel/traps.c          |   6 +-
  arch/ia64/kernel/process.c           |   4 +-
  arch/ia64/kernel/ptrace.c            |   6 +-
  arch/ia64/kernel/signal.c            |   1 -
  arch/m68k/kernel/ptrace.c            |   5 +-
  arch/m68k/kernel/signal.c            |   4 +-
  arch/microblaze/kernel/ptrace.c      |   5 +-
  arch/microblaze/kernel/signal.c      |   4 +-
  arch/mips/kernel/ptrace.c            |   5 +-
  arch/mips/kernel/signal.c            |   4 +-
  arch/nds32/include/asm/syscall.h     |   2 +-
  arch/nds32/kernel/ptrace.c           |   5 +-
  arch/nds32/kernel/signal.c           |   4 +-
  arch/nios2/kernel/ptrace.c           |   5 +-
  arch/nios2/kernel/signal.c           |   4 +-
  arch/openrisc/kernel/ptrace.c        |   5 +-
  arch/openrisc/kernel/signal.c        |   4 +-
  arch/parisc/kernel/ptrace.c          |   7 +-
  arch/parisc/kernel/signal.c          |   4 +-
  arch/powerpc/kernel/ptrace/ptrace.c  |   8 +-
  arch/powerpc/kernel/signal.c         |   4 +-
  arch/riscv/kernel/ptrace.c           |   5 +-
  arch/riscv/kernel/signal.c           |   4 +-
  arch/s390/include/asm/entry-common.h |   1 -
  arch/s390/kernel/ptrace.c            |   1 -
  arch/s390/kernel/signal.c            |   5 +-
  arch/sh/kernel/ptrace_32.c           |   5 +-
  arch/sh/kernel/signal_32.c           |   4 +-
  arch/sparc/kernel/ptrace_32.c        |   5 +-
  arch/sparc/kernel/ptrace_64.c        |   5 +-
  arch/sparc/kernel/signal32.c         |   1 -
  arch/sparc/kernel/signal_32.c        |   4 +-
  arch/sparc/kernel/signal_64.c        |   4 +-
  arch/um/kernel/process.c             |   4 +-
  arch/um/kernel/ptrace.c              |   5 +-
  arch/x86/kernel/ptrace.c             |   1 -
  arch/x86/kernel/signal.c             |   5 +-
  arch/x86/mm/tlb.c                    |   1 +
  arch/xtensa/kernel/ptrace.c          |   5 +-
  arch/xtensa/kernel/signal.c          |   4 +-
  block/blk-cgroup.c                   |   2 +-
  fs/coredump.c                        |   1 -
  fs/exec.c                            |   1 -
  fs/io-wq.c                           |   6 +-
  fs/io_uring.c                        |  11 +-
  fs/proc/array.c                      |   1 -
  fs/proc/base.c                       |   1 -
  include/asm-generic/syscall.h        |   2 +-
  include/linux/entry-common.h         |  47 +-------
  include/linux/entry-kvm.h            |   2 +-
  include/linux/posix-timers.h         |   1 -
  include/linux/ptrace.h               |  81 ++++++++++++-
  include/linux/resume_user_mode.h     |  64 ++++++++++
  include/linux/sched/signal.h         |  17 +++
  include/linux/task_work.h            |   5 +
  include/linux/tracehook.h            | 226 -----------------------------------
  include/uapi/linux/ptrace.h          |   2 +-
  kernel/entry/common.c                |  19 +--
  kernel/entry/kvm.c                   |   9 +-
  kernel/exit.c                        |   3 +-
  kernel/livepatch/transition.c        |   1 -
  kernel/ptrace.c                      |  47 +++++---
  kernel/seccomp.c                     |   1 -
  kernel/signal.c                      |  62 +++++-----
  kernel/task_work.c                   |   4 +-
  kernel/time/posix-cpu-timers.c       |   1 +
  mm/memcontrol.c                      |   2 +-
  security/apparmor/domain.c           |   1 -
  security/selinux/hooks.c             |   1 -
  85 files changed, 372 insertions(+), 495 deletions(-)
 
 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull ptrace cleanups from Eric Biederman:
 "This set of changes removes tracehook.h, moves modification of all of
  the ptrace fields inside of siglock to remove races, adds a missing
  permission check to ptrace.c

  The removal of tracehook.h is quite significant as it has been a major
  source of confusion in recent years. Much of that confusion was around
  task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the
  semantics clearer).

  For people who don't know tracehook.h is a vestiage of an attempt to
  implement uprobes like functionality that was never fully merged, and
  was later superseeded by uprobes when uprobes was merged. For many
  years now we have been removing what tracehook functionaly a little
  bit at a time. To the point where anything left in tracehook.h was
  some weird strange thing that was difficult to understand"

* tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ptrace: Remove duplicated include in ptrace.c
  ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
  ptrace: Return the signal to continue with from ptrace_stop
  ptrace: Move setting/clearing ptrace_message into ptrace_stop
  tracehook: Remove tracehook.h
  resume_user_mode: Move to resume_user_mode.h
  resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
  signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
  task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
  task_work: Call tracehook_notify_signal from get_signal on all architectures
  task_work: Introduce task_work_pending
  task_work: Remove unnecessary include from posix_timers.h
  ptrace: Remove tracehook_signal_handler
  ptrace: Remove arch_syscall_{enter,exit}_tracehook
  ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
  ptrace/arm: Rename tracehook_report_syscall report_syscall
  ptrace: Move ptrace_report_syscall into ptrace.h
2022-03-28 17:29:53 -07:00
Linus Torvalds 3bf03b9a08 Merge branch 'akpm' (patches from Andrew)
Merge updates from Andrew Morton:

 - A few misc subsystems: kthread, scripts, ntfs, ocfs2, block, and vfs

 - Most the MM patches which precede the patches in Willy's tree: kasan,
   pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap,
   sparsemem, vmalloc, pagealloc, memory-failure, mlock, hugetlb,
   userfaultfd, vmscan, compaction, mempolicy, oom-kill, migration, thp,
   cma, autonuma, psi, ksm, page-poison, madvise, memory-hotplug, rmap,
   zswap, uaccess, ioremap, highmem, cleanups, kfence, hmm, and damon.

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (227 commits)
  mm/damon/sysfs: remove repeat container_of() in damon_sysfs_kdamond_release()
  Docs/ABI/testing: add DAMON sysfs interface ABI document
  Docs/admin-guide/mm/damon/usage: document DAMON sysfs interface
  selftests/damon: add a test for DAMON sysfs interface
  mm/damon/sysfs: support DAMOS stats
  mm/damon/sysfs: support DAMOS watermarks
  mm/damon/sysfs: support schemes prioritization
  mm/damon/sysfs: support DAMOS quotas
  mm/damon/sysfs: support DAMON-based Operation Schemes
  mm/damon/sysfs: support the physical address space monitoring
  mm/damon/sysfs: link DAMON for virtual address spaces monitoring
  mm/damon: implement a minimal stub for sysfs-based DAMON interface
  mm/damon/core: add number of each enum type values
  mm/damon/core: allow non-exclusive DAMON start/stop
  Docs/damon: update outdated term 'regions update interval'
  Docs/vm/damon/design: update DAMON-Idle Page Tracking interference handling
  Docs/vm/damon: call low level monitoring primitives the operations
  mm/damon: remove unnecessary CONFIG_DAMON option
  mm/damon/paddr,vaddr: remove damon_{p,v}a_{target_valid,set_operations}()
  mm/damon/dbgfs-test: fix is_target_id() change
  ...
2022-03-22 16:11:53 -07:00
Huang Ying c574bbe917 NUMA balancing: optimize page placement for memory tiering system
With the advent of various new memory types, some machines will have
multiple types of memory, e.g.  DRAM and PMEM (persistent memory).  The
memory subsystem of these machines can be called memory tiering system,
because the performance of the different types of memory are usually
different.

In such system, because of the memory accessing pattern changing etc,
some pages in the slow memory may become hot globally.  So in this
patch, the NUMA balancing mechanism is enhanced to optimize the page
placement among the different memory types according to hot/cold
dynamically.

In a typical memory tiering system, there are CPUs, fast memory and slow
memory in each physical NUMA node.  The CPUs and the fast memory will be
put in one logical node (called fast memory node), while the slow memory
will be put in another (faked) logical node (called slow memory node).
That is, the fast memory is regarded as local while the slow memory is
regarded as remote.  So it's possible for the recently accessed pages in
the slow memory node to be promoted to the fast memory node via the
existing NUMA balancing mechanism.

The original NUMA balancing mechanism will stop to migrate pages if the
free memory of the target node becomes below the high watermark.  This
is a reasonable policy if there's only one memory type.  But this makes
the original NUMA balancing mechanism almost do not work to optimize
page placement among different memory types.  Details are as follows.

It's the common cases that the working-set size of the workload is
larger than the size of the fast memory nodes.  Otherwise, it's
unnecessary to use the slow memory at all.  So, there are almost always
no enough free pages in the fast memory nodes, so that the globally hot
pages in the slow memory node cannot be promoted to the fast memory
node.  To solve the issue, we have 2 choices as follows,

a. Ignore the free pages watermark checking when promoting hot pages
   from the slow memory node to the fast memory node.  This will
   create some memory pressure in the fast memory node, thus trigger
   the memory reclaiming.  So that, the cold pages in the fast memory
   node will be demoted to the slow memory node.

b. Define a new watermark called wmark_promo which is higher than
   wmark_high, and have kswapd reclaiming pages until free pages reach
   such watermark.  The scenario is as follows: when we want to promote
   hot-pages from a slow memory to a fast memory, but fast memory's free
   pages would go lower than high watermark with such promotion, we wake
   up kswapd with wmark_promo watermark in order to demote cold pages and
   free us up some space.  So, next time we want to promote hot-pages we
   might have a chance of doing so.

The choice "a" may create high memory pressure in the fast memory node.
If the memory pressure of the workload is high, the memory pressure
may become so high that the memory allocation latency of the workload
is influenced, e.g.  the direct reclaiming may be triggered.

The choice "b" works much better at this aspect.  If the memory
pressure of the workload is high, the hot pages promotion will stop
earlier because its allocation watermark is higher than that of the
normal memory allocation.  So in this patch, choice "b" is implemented.
A new zone watermark (WMARK_PROMO) is added.  Which is larger than the
high watermark and can be controlled via watermark_scale_factor.

In addition to the original page placement optimization among sockets,
the NUMA balancing mechanism is extended to be used to optimize page
placement according to hot/cold among different memory types.  So the
sysctl user space interface (numa_balancing) is extended in a backward
compatible way as follow, so that the users can enable/disable these
functionality individually.

The sysctl is converted from a Boolean value to a bits field.  The
definition of the flags is,

- 0: NUMA_BALANCING_DISABLED
- 1: NUMA_BALANCING_NORMAL
- 2: NUMA_BALANCING_MEMORY_TIERING

We have tested the patch with the pmbench memory accessing benchmark
with the 80:20 read/write ratio and the Gauss access address
distribution on a 2 socket Intel server with Optane DC Persistent
Memory Model.  The test results shows that the pmbench score can
improve up to 95.9%.

Thanks Andrew Morton to help fix the document format error.

Link: https://lkml.kernel.org/r/20220221084529.1052339-3-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Feng Tang <feng.tang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:09 -07:00
Linus Torvalds 3fe2f7446f Changes in this cycle were:
- Cleanups for SCHED_DEADLINE
  - Tracing updates/fixes
  - CPU Accounting fixes
  - First wave of changes to optimize the overhead of the scheduler build,
    from the fast-headers tree - including placeholder *_api.h headers for
    later header split-ups.
  - Preempt-dynamic using static_branch() for ARM64
  - Isolation housekeeping mask rework; preperatory for further changes
  - NUMA-balancing: deal with CPU-less nodes
  - NUMA-balancing: tune systems that have multiple LLC cache domains per node (eg. AMD)
  - Updates to RSEQ UAPI in preparation for glibc usage
  - Lots of RSEQ/selftests, for same
  - Add Suren as PSI co-maintainer
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Cleanups for SCHED_DEADLINE

 - Tracing updates/fixes

 - CPU Accounting fixes

 - First wave of changes to optimize the overhead of the scheduler
   build, from the fast-headers tree - including placeholder *_api.h
   headers for later header split-ups.

 - Preempt-dynamic using static_branch() for ARM64

 - Isolation housekeeping mask rework; preperatory for further changes

 - NUMA-balancing: deal with CPU-less nodes

 - NUMA-balancing: tune systems that have multiple LLC cache domains per
   node (eg. AMD)

 - Updates to RSEQ UAPI in preparation for glibc usage

 - Lots of RSEQ/selftests, for same

 - Add Suren as PSI co-maintainer

* tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (81 commits)
  sched/headers: ARM needs asm/paravirt_api_clock.h too
  sched/numa: Fix boot crash on arm64 systems
  headers/prep: Fix header to build standalone: <linux/psi.h>
  sched/headers: Only include <linux/entry-common.h> when CONFIG_GENERIC_ENTRY=y
  cgroup: Fix suspicious rcu_dereference_check() usage warning
  sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers
  sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains
  sched/deadline,rt: Remove unused parameter from pick_next_[rt|dl]_entity()
  sched/deadline,rt: Remove unused functions for !CONFIG_SMP
  sched/deadline: Use __node_2_[pdl|dle]() and rb_first_cached() consistently
  sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()
  sched/deadline: Move bandwidth mgmt and reclaim functions into sched class source file
  sched/deadline: Remove unused def_dl_bandwidth
  sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE
  sched/tracing: Don't re-read p->state when emitting sched_switch event
  sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race
  sched/cpuacct: Remove redundant RCU read lock
  sched/cpuacct: Optimize away RCU read lock
  sched/cpuacct: Fix charge percpu cpuusage
  sched/headers: Reorganize, clean up and optimize kernel/sched/sched.h dependencies
  ...
2022-03-22 14:39:12 -07:00
Huang, Ying ab31c7fd2d sched/numa: Fix boot crash on arm64 systems
Qian Cai reported a boot crash on arm64 systems, caused by:

  0fb3978b0a ("sched/numa: Fix NUMA topology for systems with CPU-less nodes")

The bug is that node_state() must be supplied a valid node_states[] array index,
but in task_numa_placement() the max_nid search can fail with NUMA_NO_NODE,
which is not a valid index.

Fix it by checking that max_nid is a valid index.

[ mingo: Added changelog. ]

Fixes: 0fb3978b0a ("sched/numa: Fix NUMA topology for systems with CPU-less nodes")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-03-22 08:49:22 +01:00
Linus Torvalds 616355cc81 for-5.18/block-2022-03-18
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Merge tag 'for-5.18/block-2022-03-18' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:

 - BFQ cleanups and fixes (Yu, Zhang, Yahu, Paolo)

 - blk-rq-qos completion fix (Tejun)

 - blk-cgroup merge fix (Tejun)

 - Add offline error return value to distinguish it from an IO error on
   the device (Song)

 - IO stats fixes (Zhang, Christoph)

 - blkcg refcount fixes (Ming, Yu)

 - Fix for indefinite dispatch loop softlockup (Shin'ichiro)

 - blk-mq hardware queue management improvements (Ming)

 - sbitmap dead code removal (Ming, John)

 - Plugging merge improvements (me)

 - Show blk-crypto capabilities in sysfs (Eric)

 - Multiple delayed queue run improvement (David)

 - Block throttling fixes (Ming)

 - Start deprecating auto module loading based on dev_t (Christoph)

 - bio allocation improvements (Christoph, Chaitanya)

 - Get rid of bio_devname (Christoph)

 - bio clone improvements (Christoph)

 - Block plugging improvements (Christoph)

 - Get rid of genhd.h header (Christoph)

 - Ensure drivers use appropriate flush helpers (Christoph)

 - Refcounting improvements (Christoph)

 - Queue initialization and teardown improvements (Ming, Christoph)

 - Misc fixes/improvements (Barry, Chaitanya, Colin, Dan, Jiapeng,
   Lukas, Nian, Yang, Eric, Chengming)

* tag 'for-5.18/block-2022-03-18' of git://git.kernel.dk/linux-block: (127 commits)
  block: cancel all throttled bios in del_gendisk()
  block: let blkcg_gq grab request queue's refcnt
  block: avoid use-after-free on throttle data
  block: limit request dispatch loop duration
  block/bfq-iosched: Fix spelling mistake "tenative" -> "tentative"
  sr: simplify the local variable initialization in sr_block_open()
  block: don't merge across cgroup boundaries if blkcg is enabled
  block: fix rq-qos breakage from skipping rq_qos_done_bio()
  block: flush plug based on hardware and software queue order
  block: ensure plug merging checks the correct queue at least once
  block: move rq_qos_exit() into disk_release()
  block: do more work in elevator_exit
  block: move blk_exit_queue into disk_release
  block: move q_usage_counter release into blk_queue_release
  block: don't remove hctx debugfs dir from blk_mq_exit_queue
  block: move blkcg initialization/destroy into disk allocation/release handler
  sr: implement ->free_disk to simplify refcounting
  sd: implement ->free_disk to simplify refcounting
  sd: delay calling free_opal_dev
  sd: call sd_zbc_release_disk before releasing the scsi_device reference
  ...
2022-03-21 16:48:55 -07:00
Ingo Molnar a7b2553b5e sched/headers: Only include <linux/entry-common.h> when CONFIG_GENERIC_ENTRY=y
This header is not (yet) standalone.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-03-15 10:33:53 +01:00
Ingo Molnar ccacfe56d7 Merge branch 'sched/fast-headers' into sched/core
Merge the scheduler build speedup of the fast-headers tree.

Cumulative scheduler (kernel/sched/) build time speedup on a
Linux distribution's config, which enables all scheduler features,
compared to the vanilla kernel:

      _____________________________________________________________________________
     |
     |  Vanilla kernel (v5.13-rc7):
     |_____________________________________________________________________________
     |
     |  Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
     |
     |   126,975,564,374      instructions              #    1.45  insn per cycle           ( +-  0.00% )
     |    87,637,847,671      cycles                    #    3.959 GHz                      ( +-  0.30% )
     |         22,136.96 msec cpu-clock                 #    7.499 CPUs utilized            ( +-  0.29% )
     |
     |            2.9520 +- 0.0169 seconds time elapsed  ( +-  0.57% )
     |_____________________________________________________________________________
     |
     |  Patched kernel:
     |_____________________________________________________________________________
     |
     | Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
     |
     |    50,420,496,914      instructions              #    1.47  insn per cycle           ( +-  0.00% )
     |    34,234,322,038      cycles                    #    3.946 GHz                      ( +-  0.31% )
     |          8,675.81 msec cpu-clock                 #    3.053 CPUs utilized            ( +-  0.45% )
     |
     |            2.8420 +- 0.0181 seconds time elapsed  ( +-  0.64% )
     |_____________________________________________________________________________

    Summary:

      - CPU time used to build the scheduler dropped by -60.9%, a reduction
        from 22.1 clock-seconds to 8.7 clock-seconds.

      - Wall-clock time to build the scheduler dropped by -3.9%, a reduction
        from 2.95 seconds to 2.84 seconds.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-03-15 09:05:05 +01:00
K Prateek Nayak 7f434dff76 sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains
While investigating the sparse warning reported by the LKP bot [1],
observed that we have a redundant variable "top" in the function
build_sched_domains that was introduced in the recent commit
e496132ebe ("sched/fair: Adjust the allowed NUMA imbalance when
SD_NUMA spans multiple LLCs")

The existing variable "sd" suffices which allows us to remove the
redundant variable "top" while annotating the other variable "top_p"
with the "__rcu" annotation to silence the sparse warning.

[1] https://lore.kernel.org/lkml/202202170853.9vofgC3O-lkp@intel.com/

Fixes: e496132ebe ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20220218162743.1134-1-kprateek.nayak@amd.com
2022-03-08 16:08:40 +01:00
Dietmar Eggemann 821aecd09e sched/deadline,rt: Remove unused parameter from pick_next_[rt|dl]_entity()
The `struct rq *rq` parameter isn't used. Remove it.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-7-dietmar.eggemann@arm.com
2022-03-08 16:08:40 +01:00
Dietmar Eggemann 71d29747b0 sched/deadline,rt: Remove unused functions for !CONFIG_SMP
The need_pull_[rt|dl]_task() and pull_[rt|dl]_task() functions are not
used on a !CONFIG_SMP system. Remove them.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-6-dietmar.eggemann@arm.com
2022-03-08 16:08:39 +01:00
Dietmar Eggemann f4478e7c85 sched/deadline: Use __node_2_[pdl|dle]() and rb_first_cached() consistently
Deploy __node_2_pdl(node), __node_2_dle(node) and rb_first_cached()
consistently throughout the sched class source file which makes the
code at least easier to read.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-5-dietmar.eggemann@arm.com
2022-03-08 16:08:39 +01:00
Dietmar Eggemann 772b6539fd sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()
Both functions are doing almost the same, that is checking if admission
control is still respected.

With exclusive cpusets, dl_task_can_attach() checks if the destination
cpuset (i.e. its root domain) has enough CPU capacity to accommodate the
task.
dl_cpu_busy() checks if there is enough CPU capacity in the cpuset in
case the CPU is hot-plugged out.

dl_task_can_attach() is used to check if a task can be admitted while
dl_cpu_busy() is used to check if a CPU can be hotplugged out.

Make dl_cpu_busy() able to deal with a task and use it instead of
dl_task_can_attach() in task_can_attach().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-4-dietmar.eggemann@arm.com
2022-03-08 16:08:39 +01:00
Dietmar Eggemann f1304ecbef sched/deadline: Move bandwidth mgmt and reclaim functions into sched class source file
Move the deadline bandwidth management (admission control) functions
__dl_add(), __dl_sub() and __dl_overflow() as well as the bandwidth
reclaim function __dl_update() from private task scheduler header file
to the deadline sched class source file.
The functions are only used internally so they don't have to be
exported.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-3-dietmar.eggemann@arm.com
2022-03-08 16:08:39 +01:00
Dietmar Eggemann eb77cf1c15 sched/deadline: Remove unused def_dl_bandwidth
Since commit 1724813d9f ("sched/deadline: Remove the sysctl_sched_dl
knobs") the default deadline bandwidth control structure has no purpose.
Remove it.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-2-dietmar.eggemann@arm.com
2022-03-08 16:08:38 +01:00
Valentin Schneider fa2c3254d7 sched/tracing: Don't re-read p->state when emitting sched_switch event
As of commit

  c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")

the following sequence becomes possible:

		      p->__state = TASK_INTERRUPTIBLE;
		      __schedule()
			deactivate_task(p);
  ttwu()
    READ !p->on_rq
    p->__state=TASK_WAKING
			trace_sched_switch()
			  __trace_sched_switch_state()
			    task_state_index()
			      return 0;

TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
the trace event.

Prevent this by pushing the value read from __schedule() down the trace
event.

Reported-by: Abhijeet Dharmapurikar <adharmap@quicinc.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com
2022-03-01 16:18:39 +01:00
Valentin Schneider 49bef33e4b sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race
John reported that push_rt_task() can end up invoking
find_lowest_rq(rq->curr) when curr is not an RT task (in this case a CFS
one), which causes mayhem down convert_prio().

This can happen when current gets demoted to e.g. CFS when releasing an
rt_mutex, and the local CPU gets hit with an rto_push_work irqwork before
getting the chance to reschedule. Exactly who triggers this work isn't
entirely clear to me - switched_from_rt() only invokes rt_queue_pull_task()
if there are no RT tasks on the local RQ, which means the local CPU can't
be in the rto_mask.

My current suspected sequence is something along the lines of the below,
with the demoted task being current.

  mark_wakeup_next_waiter()
    rt_mutex_adjust_prio()
      rt_mutex_setprio() // deboost originally-CFS task
	check_class_changed()
	  switched_from_rt() // Only rt_queue_pull_task() if !rq->rt.rt_nr_running
	  switched_to_fair() // Sets need_resched
      __balance_callbacks() // if pull_rt_task(), tell_cpu_to_push() can't select local CPU per the above
      raw_spin_rq_unlock(rq)

       // need_resched is set, so task_woken_rt() can't
       // invoke push_rt_tasks(). Best I can come up with is
       // local CPU has rt_nr_migratory >= 2 after the demotion, so stays
       // in the rto_mask, and then:

       <some other CPU running rto_push_irq_work_func() queues rto_push_work on this CPU>
	 push_rt_task()
	   // breakage follows here as rq->curr is CFS

Move an existing check to check rq->curr vs the next pushable task's
priority before getting anywhere near find_lowest_rq(). While at it, add an
explicit sched_class of rq->curr check prior to invoking
find_lowest_rq(rq->curr). Align the DL logic to also reschedule regardless
of next_task's migratability.

Fixes: a7c81556ec ("sched: Fix migrate_disable() vs rt/dl balancing")
Reported-by: John Keeping <john@metanate.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20220127154059.974729-1-valentin.schneider@arm.com
2022-03-01 16:18:38 +01:00
Chengming Zhou 3eba0505d0 sched/cpuacct: Remove redundant RCU read lock
The cpuacct_account_field() and it's cgroup v2 wrapper
cgroup_account_cputime_field() is only called from cputime
in task_group_account_field(), which is already in RCU read-side
critical section. So remove these redundant RCU read lock.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220220051426.5274-3-zhouchengming@bytedance.com
2022-03-01 16:18:38 +01:00
Chengming Zhou dc6e0818bc sched/cpuacct: Optimize away RCU read lock
Since cpuacct_charge() is called from the scheduler update_curr(),
we must already have rq lock held, then the RCU read lock can
be optimized away.

And do the same thing in it's wrapper cgroup_account_cputime(),
but we can't use lockdep_assert_rq_held() there, which defined
in kernel/sched/sched.h.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220220051426.5274-2-zhouchengming@bytedance.com
2022-03-01 16:18:38 +01:00
Chengming Zhou 248cc9993d sched/cpuacct: Fix charge percpu cpuusage
The cpuacct_account_field() is always called by the current task
itself, so it's ok to use __this_cpu_add() to charge the tick time.

But cpuacct_charge() maybe called by update_curr() in load_balance()
on a random CPU, different from the CPU on which the task is running.
So __this_cpu_add() will charge that cputime to a random incorrect CPU.

Fixes: 73e6aafd9e ("sched/cpuacct: Simplify the cpuacct code")
Reported-by: Minye Zhu <zhuminye@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220220051426.5274-1-zhouchengming@bytedance.com
2022-03-01 16:18:37 +01:00
Rafael J. Wysocki 075c3c483c Merge back cpufreq changes for v5.18. 2022-02-28 20:47:57 +01:00
Ingo Molnar 4ff8f2ca6c sched/headers: Reorganize, clean up and optimize kernel/sched/sched.h dependencies
Remove all headers, except the ones required to make this header
build standalone.

Also include stats.h in sched.h explicitly - dependencies already
require this.

Summary of the build speedup gained through the last ~15 scheduler build &
header dependency patches:

Cumulative scheduler (kernel/sched/) build time speedup on a
Linux distribution's config, which enables all scheduler features,
compared to the vanilla kernel:

  _____________________________________________________________________________
 |
 |  Vanilla kernel (v5.13-rc7):
 |_____________________________________________________________________________
 |
 |  Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
 |
 |   126,975,564,374      instructions              #    1.45  insn per cycle           ( +-  0.00% )
 |    87,637,847,671      cycles                    #    3.959 GHz                      ( +-  0.30% )
 |         22,136.96 msec cpu-clock                 #    7.499 CPUs utilized            ( +-  0.29% )
 |
 |            2.9520 +- 0.0169 seconds time elapsed  ( +-  0.57% )
 |_____________________________________________________________________________
 |
 |  Patched kernel:
 |_____________________________________________________________________________
 |
 | Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
 |
 |    50,420,496,914      instructions              #    1.47  insn per cycle           ( +-  0.00% )
 |    34,234,322,038      cycles                    #    3.946 GHz                      ( +-  0.31% )
 |          8,675.81 msec cpu-clock                 #    3.053 CPUs utilized            ( +-  0.45% )
 |
 |            2.8420 +- 0.0181 seconds time elapsed  ( +-  0.64% )
 |_____________________________________________________________________________

Summary:

  - CPU time used to build the scheduler dropped by -60.9%, a reduction
    from 22.1 clock-seconds to 8.7 clock-seconds.

  - Wall-clock time to build the scheduler dropped by -3.9%, a reduction
    from 2.95 seconds to 2.84 seconds.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:34 +01:00
Ingo Molnar e81daa7b64 sched/headers: Reorganize, clean up and optimize kernel/sched/build_utility.c dependencies
Use all generic headers from kernel/sched/sched.h that are required
for it to build.

Sort the sections alphabetically.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:34 +01:00
Ingo Molnar 0dda4eeb48 sched/headers: Reorganize, clean up and optimize kernel/sched/build_policy.c dependencies
Use all generic headers from kernel/sched/sched.h that are required
for it to build.

Sort the sections alphabetically.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar c4ad6fcb67 sched/headers: Reorganize, clean up and optimize kernel/sched/fair.c dependencies
Use all generic headers from kernel/sched/sched.h that are required
for it to build.

Sort the sections alphabetically.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar e66f6481a8 sched/headers: Reorganize, clean up and optimize kernel/sched/core.c dependencies
Use all generic headers from kernel/sched/sched.h that are required
for it to build.

Sort the sections alphabetically.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar b9e9c6ca6e sched/headers: Standardize kernel/sched/sched.h header dependencies
kernel/sched/sched.h is a weird mix of ad-hoc headers included
in the middle of the header.

Two of them rely on being included in the middle of kernel/sched/sched.h,
due to definitions they require:

 - "stat.h" needs the rq definitions.
 - "autogroup.h" needs the task_group definition.

Move the inclusion of these two files out of kernel/sched/sched.h, and
include them in all files that require them.

Move of the rest of the header dependencies to the top of the
kernel/sched/sched.h file.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar f96eca4320 sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there
Similarly to kernel/sched/build_utility.c, collect all 'scheduling policy' related
source code files into kernel/sched/build_policy.c:

    kernel/sched/idle.c

    kernel/sched/rt.c

    kernel/sched/cpudeadline.c
    kernel/sched/pelt.c

    kernel/sched/cputime.c
    kernel/sched/deadline.c

With the exception of fair.c, which we continue to build as a separate file
for build efficiency and parallelism reasons.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar 801c141955 sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there
Collect all utility functionality source code files into a single kernel/sched/build_utility.c file,
via #include-ing the .c files:

    kernel/sched/clock.c
    kernel/sched/completion.c
    kernel/sched/loadavg.c
    kernel/sched/swait.c
    kernel/sched/wait_bit.c
    kernel/sched/wait.c

CONFIG_CPU_FREQ:
    kernel/sched/cpufreq.c

CONFIG_CPU_FREQ_GOV_SCHEDUTIL:
    kernel/sched/cpufreq_schedutil.c

CONFIG_CGROUP_CPUACCT:
    kernel/sched/cpuacct.c

CONFIG_SCHED_DEBUG:
    kernel/sched/debug.c

CONFIG_SCHEDSTATS:
    kernel/sched/stats.c

CONFIG_SMP:
   kernel/sched/cpupri.c
   kernel/sched/stop_task.c
   kernel/sched/topology.c

CONFIG_SCHED_CORE:
   kernel/sched/core_sched.c

CONFIG_PSI:
   kernel/sched/psi.c

CONFIG_MEMBARRIER:
   kernel/sched/membarrier.c

CONFIG_CPU_ISOLATION:
   kernel/sched/isolation.c

CONFIG_SCHED_AUTOGROUP:
   kernel/sched/autogroup.c

The goal is to amortize the 60+ KLOC header bloat from over a dozen build units into
a single build unit.

The build time of build_utility.c also roughly matches the build time of core.c and
fair.c - allowing better load-balancing of scheduler-only rebuilds.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar 81de6572fe sched/headers: Fix comment typo in kernel/sched/cpudeadline.c
File name changed.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar fa28abed7a sched/headers: sched/clock: Mark all functions 'notrace', remove CC_FLAGS_FTRACE build asymmetry
Mark all non-init functions in kernel/sched.c as 'notrace', instead of
turning them all off via CC_FLAGS_FTRACE.

This is going to allow the treatment of this file as any other scheduler
file, and it can be #include-ed in compound compilation units as well.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 08:22:04 +01:00
Ingo Molnar d90a2f160a sched/headers: Add header guard to kernel/sched/stats.h and kernel/sched/autogroup.h
Protect against multiple inclusion.

Also include "sched.h" in "stat.h", as it relies on it.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 08:22:00 +01:00
Ingo Molnar 95458477f5 sched/headers: Add header guard to kernel/sched/sched.h
Use the canonical header guard naming of the full path to the header.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 08:21:56 +01:00
Ingo Molnar 6255b48aeb Linux 5.17-rc5
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Merge tag 'v5.17-rc5' into sched/core, to resolve conflicts

New conflicts in sched/core due to the following upstream fixes:

  44585f7bc0 ("psi: fix "defined but not used" warnings when CONFIG_PROC_FS=n")
  a06247c680 ("psi: Fix uaf issue when psi trigger is destroyed while being polled")

Conflicts:
	include/linux/psi_types.h
	kernel/sched/psi.c

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-02-21 11:53:51 +01:00
Mark Rutland 99cf983cc8 sched/preempt: Add PREEMPT_DYNAMIC using static keys
Where an architecture selects HAVE_STATIC_CALL but not
HAVE_STATIC_CALL_INLINE, each static call has an out-of-line trampoline
which will either branch to a callee or return to the caller.

On such architectures, a number of constraints can conspire to make
those trampolines more complicated and potentially less useful than we'd
like. For example:

* Hardware and software control flow integrity schemes can require the
  addition of "landing pad" instructions (e.g. `BTI` for arm64), which
  will also be present at the "real" callee.

* Limited branch ranges can require that trampolines generate or load an
  address into a register and perform an indirect branch (or at least
  have a slow path that does so). This loses some of the benefits of
  having a direct branch.

* Interaction with SW CFI schemes can be complicated and fragile, e.g.
  requiring that we can recognise idiomatic codegen and remove
  indirections understand, at least until clang proves more helpful
  mechanisms for dealing with this.

For PREEMPT_DYNAMIC, we don't need the full power of static calls, as we
really only need to enable/disable specific preemption functions. We can
achieve the same effect without a number of the pain points above by
using static keys to fold early returns into the preemption functions
themselves rather than in an out-of-line trampoline, effectively
inlining the trampoline into the start of the function.

For arm64, this results in good code generation. For example, the
dynamic_cond_resched() wrapper looks as follows when enabled. When
disabled, the first `B` is replaced with a `NOP`, resulting in an early
return.

| <dynamic_cond_resched>:
|        bti     c
|        b       <dynamic_cond_resched+0x10>     // or `nop`
|        mov     w0, #0x0
|        ret
|        mrs     x0, sp_el0
|        ldr     x0, [x0, #8]
|        cbnz    x0, <dynamic_cond_resched+0x8>
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mov     x29, sp
|        bl      <preempt_schedule_common>
|        mov     w0, #0x1
|        ldp     x29, x30, [sp], #16
|        autiasp
|        ret

... compared to the regular form of the function:

| <__cond_resched>:
|        bti     c
|        mrs     x0, sp_el0
|        ldr     x1, [x0, #8]
|        cbz     x1, <__cond_resched+0x18>
|        mov     w0, #0x0
|        ret
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mov     x29, sp
|        bl      <preempt_schedule_common>
|        mov     w0, #0x1
|        ldp     x29, x30, [sp], #16
|        autiasp
|        ret

Any architecture which implements static keys should be able to use this
to implement PREEMPT_DYNAMIC with similar cost to non-inlined static
calls. Since this is likely to have greater overhead than (inlined)
static calls, PREEMPT_DYNAMIC is only defaulted to enabled when
HAVE_PREEMPT_DYNAMIC_CALL is selected.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-6-mark.rutland@arm.com
2022-02-19 11:11:08 +01:00
Mark Rutland 33c64734be sched/preempt: Decouple HAVE_PREEMPT_DYNAMIC from GENERIC_ENTRY
Now that the enabled/disabled states for the preemption functions are
declared alongside their definitions, the core PREEMPT_DYNAMIC logic is
no longer tied to GENERIC_ENTRY, and can safely be selected so long as
an architecture provides enabled/disabled states for
irqentry_exit_cond_resched().

Make it possible to select HAVE_PREEMPT_DYNAMIC without GENERIC_ENTRY.

For existing users of HAVE_PREEMPT_DYNAMIC there should be no functional
change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-5-mark.rutland@arm.com
2022-02-19 11:11:08 +01:00
Mark Rutland 8a69fe0be1 sched/preempt: Refactor sched_dynamic_update()
Currently sched_dynamic_update needs to open-code the enabled/disabled
function names for each preemption model it supports, when in practice
this is a boolean enabled/disabled state for each function.

Make this clearer and avoid repetition by defining the enabled/disabled
states at the function definition, and using helper macros to perform the
static_call_update(). Where x86 currently overrides the enabled
function, it is made to provide both the enabled and disabled states for
consistency, with defaults provided by the core code otherwise.

In subsequent patches this will allow us to support PREEMPT_DYNAMIC
without static calls.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-3-mark.rutland@arm.com
2022-02-19 11:11:07 +01:00
Mark Rutland 4c7485584d sched/preempt: Move PREEMPT_DYNAMIC logic later
The PREEMPT_DYNAMIC logic in kernel/sched/core.c patches static calls
for a bunch of preemption functions. While most are defined prior to
this, the definition of cond_resched() is later in the file, and so we
only have its declarations from include/linux/sched.h.

In subsequent patches we'd like to define some macros alongside the
definition of each of the preemption functions, which we can use within
sched_dynamic_update(). For this to be possible, the PREEMPT_DYNAMIC
logic needs to be placed after the various preemption functions.

As a preparatory step, this patch moves the PREEMPT_DYNAMIC logic after
the various preemption functions, with no other changes -- this is
purely a move.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-2-mark.rutland@arm.com
2022-02-19 11:11:07 +01:00
Peter Zijlstra b1e8206582 sched: Fix yet more sched_fork() races
Where commit 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an
invalid sched_task_group") fixed a fork race vs cgroup, it opened up a
race vs syscalls by not placing the task on the runqueue before it
gets exposed through the pidhash.

Commit 13765de814 ("sched/fair: Fix fault in reweight_entity") is
trying to fix a single instance of this, instead fix the whole class
of issues, effectively reverting this commit.

Fixes: 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Tested-by: Zhang Qiao <zhangqiao22@huawei.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/YgoeCbwj5mbCR0qA@hirez.programming.kicks-ass.net
2022-02-19 11:11:05 +01:00
Frederic Weisbecker ed3b362d54 sched/isolation: Split housekeeping cpumask per isolation features
To prepare for supporting each housekeeping feature toward cpuset, split
the global housekeeping cpumask per HK_TYPE_* entry.

This will later allow, for example, to runtime modify the cpulist passed
through "isolcpus=", "nohz_full=" and "rcu_nocbs=" kernel boot
parameters.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-9-frederic@kernel.org
2022-02-16 15:57:56 +01:00
Frederic Weisbecker 65e53f869e sched/isolation: Fix housekeeping_mask memory leak
If "nohz_full=" or "isolcpus=nohz" are called with CONFIG_NO_HZ_FULL=n,
housekeeping_mask doesn't get freed despite it being unused if
housekeeping_setup() is called for the first time.

Check this scenario first to fix this, so that no useless allocation
is performed.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-8-frederic@kernel.org
2022-02-16 15:57:56 +01:00
Frederic Weisbecker 0cd3e59de1 sched/isolation: Consolidate error handling
Centralize the mask freeing and return value for the error path. This
makes potential leaks more visible.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-7-frederic@kernel.org
2022-02-16 15:57:55 +01:00
Frederic Weisbecker 6367b600e3 sched/isolation: Consolidate check for housekeeping minimum service
There can be two subsequent calls to housekeeping_setup() due to
"nohz_full=" and "isolcpus=" that can mix up.  The two passes each have
their own way to deal with an empty housekeeping set of CPUs.
Consolidate this part and remove the awful "tmp" based naming.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-6-frederic@kernel.org
2022-02-16 15:57:55 +01:00
Frederic Weisbecker 04d4e665a6 sched/isolation: Use single feature type while referring to housekeeping cpumask
Refer to housekeeping APIs using single feature types instead of flags.
This prevents from passing multiple isolation features at once to
housekeeping interfaces, which soon won't be possible anymore as each
isolation features will have their own cpumask.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-5-frederic@kernel.org
2022-02-16 15:57:55 +01:00
Zhaoyang Huang e6df4ead85 psi: fix possible trigger missing in the window
When a new threshold breaching stall happens after a psi event was
generated and within the window duration, the new event is not
generated because the events are rate-limited to one per window. If
after that no new stall is recorded then the event will not be
generated even after rate-limiting duration has passed. This is
happening because with no new stall, window_update will not be called
even though threshold was previously breached. To fix this, record
threshold breaching occurrence and generate the event once window
duration is passed.

Suggested-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Link: https://lore.kernel.org/r/1643093818-19835-1-git-send-email-huangzhaoyang@gmail.com
2022-02-16 15:57:54 +01:00
Huang Ying 5c7b1aaf13 sched/numa: Avoid migrating task to CPU-less node
In a typical memory tiering system, there's no CPU in slow (PMEM) NUMA
nodes.  But if the number of the hint page faults on a PMEM node is
the max for a task, The current NUMA balancing policy may try to place
the task on the PMEM node instead of DRAM node.  This is unreasonable,
because there's no CPU in PMEM NUMA nodes.  To fix this, CPU-less
nodes are ignored when searching the migration target node for a task
in this patch.

To test the patch, we run a workload that accesses more memory in PMEM
node than memory in DRAM node.  Without the patch, the PMEM node will
be chosen as preferred node in task_numa_placement().  While the DRAM
node will be chosen instead with the patch.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220214121553.582248-2-ying.huang@intel.com
2022-02-16 15:57:53 +01:00
Huang Ying 0fb3978b0a sched/numa: Fix NUMA topology for systems with CPU-less nodes
The NUMA topology parameters (sched_numa_topology_type,
sched_domains_numa_levels, and sched_max_numa_distance, etc.)
identified by scheduler may be wrong for systems with CPU-less nodes.

For example, the ACPI SLIT of a system with CPU-less persistent
memory (Intel Optane DCPMM) nodes is as follows,

[000h 0000   4]                    Signature : "SLIT"    [System Locality Information Table]
[004h 0004   4]                 Table Length : 0000042C
[008h 0008   1]                     Revision : 01
[009h 0009   1]                     Checksum : 59
[00Ah 0010   6]                       Oem ID : "XXXX"
[010h 0016   8]                 Oem Table ID : "XXXXXXX"
[018h 0024   4]                 Oem Revision : 00000001
[01Ch 0028   4]              Asl Compiler ID : "INTL"
[020h 0032   4]        Asl Compiler Revision : 20091013

[024h 0036   8]                   Localities : 0000000000000004
[02Ch 0044   4]                 Locality   0 : 0A 15 11 1C
[030h 0048   4]                 Locality   1 : 15 0A 1C 11
[034h 0052   4]                 Locality   2 : 11 1C 0A 1C
[038h 0056   4]                 Locality   3 : 1C 11 1C 0A

While the `numactl -H` output is as follows,

available: 4 nodes (0-3)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
node 0 size: 64136 MB
node 0 free: 5981 MB
node 1 cpus: 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
node 1 size: 64466 MB
node 1 free: 10415 MB
node 2 cpus:
node 2 size: 253952 MB
node 2 free: 253920 MB
node 3 cpus:
node 3 size: 253952 MB
node 3 free: 253951 MB
node distances:
node   0   1   2   3
  0:  10  21  17  28
  1:  21  10  28  17
  2:  17  28  10  28
  3:  28  17  28  10

In this system, there are only 2 sockets.  In each memory controller,
both DRAM and PMEM DIMMs are installed.  Although the physical NUMA
topology is simple, the logical NUMA topology becomes a little
complex.  Because both the distance(0, 1) and distance (1, 3) are less
than the distance (0, 3), it appears that node 1 sits between node 0
and node 3.  And the whole system appears to be a glueless mesh NUMA
topology type.  But it's definitely not, there is even no CPU in node 3.

This isn't a practical problem now yet.  Because the PMEM nodes (node
2 and node 3 in example system) are offlined by default during system
boot.  So init_numa_topology_type() called during system boot will
ignore them and set sched_numa_topology_type to NUMA_DIRECT.  And
init_numa_topology_type() is only called at runtime when a CPU of a
never-onlined-before node gets plugged in.  And there's no CPU in the
PMEM nodes.  But it appears better to fix this to make the code more
robust.

To test the potential problem.  We have used a debug patch to call
init_numa_topology_type() when the PMEM node is onlined (in
__set_migration_target_nodes()).  With that, the NUMA parameters
identified by scheduler is as follows,

sched_numa_topology_type:	NUMA_GLUELESS_MESH
sched_domains_numa_levels:	4
sched_max_numa_distance:	28

To fix the issue, the CPU-less nodes are ignored when the NUMA topology
parameters are identified.  Because a node may become CPU-less or not
at run time because of CPU hotplug, the NUMA topology parameters need
to be re-initialized at runtime for CPU hotplug too.

With the patch, the NUMA parameters identified for the example system
above is as follows,

sched_numa_topology_type:	NUMA_DIRECT
sched_domains_numa_levels:	2
sched_max_numa_distance:	21

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220214121553.582248-1-ying.huang@intel.com
2022-02-16 15:57:53 +01:00
Yury Norov 1087ad4e3f sched: replace cpumask_weight with cpumask_empty where appropriate
In some places, kernel/sched code calls cpumask_weight() to check if
any bit of a given cpumask is set. We can do it more efficiently with
cpumask_empty() because cpumask_empty() stops traversing the cpumask as
soon as it finds first set bit, while cpumask_weight() counts all bits
unconditionally.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220210224933.379149-23-yury.norov@gmail.com
2022-02-16 15:57:53 +01:00
Mel Gorman e496132ebe sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs
Commit 7d2b5dd0bc ("sched/numa: Allow a floating imbalance between NUMA
nodes") allowed an imbalance between NUMA nodes such that communicating
tasks would not be pulled apart by the load balancer. This works fine when
there is a 1:1 relationship between LLC and node but can be suboptimal
for multiple LLCs if independent tasks prematurely use CPUs sharing cache.

Zen* has multiple LLCs per node with local memory channels and due to
the allowed imbalance, it's far harder to tune some workloads to run
optimally than it is on hardware that has 1 LLC per node. This patch
allows an imbalance to exist up to the point where LLCs should be balanced
between nodes.

On a Zen3 machine running STREAM parallelised with OMP to have on instance
per LLC the results and without binding, the results are

                            5.17.0-rc0             5.17.0-rc0
                               vanilla       sched-numaimb-v6
MB/sec copy-16    162596.94 (   0.00%)   580559.74 ( 257.05%)
MB/sec scale-16   136901.28 (   0.00%)   374450.52 ( 173.52%)
MB/sec add-16     157300.70 (   0.00%)   564113.76 ( 258.62%)
MB/sec triad-16   151446.88 (   0.00%)   564304.24 ( 272.61%)

STREAM can use directives to force the spread if the OpenMP is new
enough but that doesn't help if an application uses threads and
it's not known in advance how many threads will be created.

Coremark is a CPU and cache intensive benchmark parallelised with
threads. When running with 1 thread per core, the vanilla kernel
allows threads to contend on cache. With the patch;

                               5.17.0-rc0             5.17.0-rc0
                                  vanilla       sched-numaimb-v5
Min       Score-16   368239.36 (   0.00%)   389816.06 (   5.86%)
Hmean     Score-16   388607.33 (   0.00%)   427877.08 *  10.11%*
Max       Score-16   408945.69 (   0.00%)   481022.17 (  17.62%)
Stddev    Score-16    15247.04 (   0.00%)    24966.82 ( -63.75%)
CoeffVar  Score-16        3.92 (   0.00%)        5.82 ( -48.48%)

It can also make a big difference for semi-realistic workloads
like specjbb which can execute arbitrary numbers of threads without
advance knowledge of how they should be placed. Even in cases where
the average performance is neutral, the results are more stable.

                               5.17.0-rc0             5.17.0-rc0
                                  vanilla       sched-numaimb-v6
Hmean     tput-1      71631.55 (   0.00%)    73065.57 (   2.00%)
Hmean     tput-8     582758.78 (   0.00%)   556777.23 (  -4.46%)
Hmean     tput-16   1020372.75 (   0.00%)  1009995.26 (  -1.02%)
Hmean     tput-24   1416430.67 (   0.00%)  1398700.11 (  -1.25%)
Hmean     tput-32   1687702.72 (   0.00%)  1671357.04 (  -0.97%)
Hmean     tput-40   1798094.90 (   0.00%)  2015616.46 *  12.10%*
Hmean     tput-48   1972731.77 (   0.00%)  2333233.72 (  18.27%)
Hmean     tput-56   2386872.38 (   0.00%)  2759483.38 (  15.61%)
Hmean     tput-64   2909475.33 (   0.00%)  2925074.69 (   0.54%)
Hmean     tput-72   2585071.36 (   0.00%)  2962443.97 (  14.60%)
Hmean     tput-80   2994387.24 (   0.00%)  3015980.59 (   0.72%)
Hmean     tput-88   3061408.57 (   0.00%)  3010296.16 (  -1.67%)
Hmean     tput-96   3052394.82 (   0.00%)  2784743.41 (  -8.77%)
Hmean     tput-104  2997814.76 (   0.00%)  2758184.50 (  -7.99%)
Hmean     tput-112  2955353.29 (   0.00%)  2859705.09 (  -3.24%)
Hmean     tput-120  2889770.71 (   0.00%)  2764478.46 (  -4.34%)
Hmean     tput-128  2871713.84 (   0.00%)  2750136.73 (  -4.23%)
Stddev    tput-1       5325.93 (   0.00%)     2002.53 (  62.40%)
Stddev    tput-8       6630.54 (   0.00%)    10905.00 ( -64.47%)
Stddev    tput-16     25608.58 (   0.00%)     6851.16 (  73.25%)
Stddev    tput-24     12117.69 (   0.00%)     4227.79 (  65.11%)
Stddev    tput-32     27577.16 (   0.00%)     8761.05 (  68.23%)
Stddev    tput-40     59505.86 (   0.00%)     2048.49 (  96.56%)
Stddev    tput-48    168330.30 (   0.00%)    93058.08 (  44.72%)
Stddev    tput-56    219540.39 (   0.00%)    30687.02 (  86.02%)
Stddev    tput-64    121750.35 (   0.00%)     9617.36 (  92.10%)
Stddev    tput-72    223387.05 (   0.00%)    34081.13 (  84.74%)
Stddev    tput-80    128198.46 (   0.00%)    22565.19 (  82.40%)
Stddev    tput-88    136665.36 (   0.00%)    27905.97 (  79.58%)
Stddev    tput-96    111925.81 (   0.00%)    99615.79 (  11.00%)
Stddev    tput-104   146455.96 (   0.00%)    28861.98 (  80.29%)
Stddev    tput-112    88740.49 (   0.00%)    58288.23 (  34.32%)
Stddev    tput-120   186384.86 (   0.00%)    45812.03 (  75.42%)
Stddev    tput-128    78761.09 (   0.00%)    57418.48 (  27.10%)

Similarly, for embarassingly parallel problems like NPB-ep, there are
improvements due to better spreading across LLC when the machine is not
fully utilised.

                              vanilla       sched-numaimb-v6
Min       ep.D       31.79 (   0.00%)       26.11 (  17.87%)
Amean     ep.D       31.86 (   0.00%)       26.17 *  17.86%*
Stddev    ep.D        0.07 (   0.00%)        0.05 (  24.41%)
CoeffVar  ep.D        0.22 (   0.00%)        0.20 (   7.97%)
Max       ep.D       31.93 (   0.00%)       26.21 (  17.91%)

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20220208094334.16379-3-mgorman@techsingularity.net
2022-02-11 23:30:08 +01:00
Mel Gorman 2cfb7a1b03 sched/fair: Improve consistency of allowed NUMA balance calculations
There are inconsistencies when determining if a NUMA imbalance is allowed
that should be corrected.

o allow_numa_imbalance changes types and is not always examining
  the destination group so both the type should be corrected as
  well as the naming.
o find_idlest_group uses the sched_domain's weight instead of the
  group weight which is different to find_busiest_group
o find_busiest_group uses the source group instead of the destination
  which is different to task_numa_find_cpu
o Both find_idlest_group and find_busiest_group should account
  for the number of running tasks if a move was allowed to be
  consistent with task_numa_find_cpu

Fixes: 7d2b5dd0bc ("sched/numa: Allow a floating imbalance between NUMA nodes")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20220208094334.16379-2-mgorman@techsingularity.net
2022-02-11 23:30:08 +01:00
Tadeusz Struk 13765de814 sched/fair: Fix fault in reweight_entity
Syzbot found a GPF in reweight_entity. This has been bisected to
commit 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid
sched_task_group")

There is a race between sched_post_fork() and setpriority(PRIO_PGRP)
within a thread group that causes a null-ptr-deref in
reweight_entity() in CFS. The scenario is that the main process spawns
number of new threads, which then call setpriority(PRIO_PGRP, 0, -20),
wait, and exit.  For each of the new threads the copy_process() gets
invoked, which adds the new task_struct and calls sched_post_fork()
for it.

In the above scenario there is a possibility that
setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread
in the group that is just being created by copy_process(), and for
which the sched_post_fork() has not been executed yet. This will
trigger a null pointer dereference in reweight_entity(), as it will
try to access the run queue pointer, which hasn't been set.

Before the mentioned change the cfs_rq pointer for the task  has been
set in sched_fork(), which is called much earlier in copy_process(),
before the new task is added to the thread_group.  Now it is done in
the sched_post_fork(), which is called after that.  To fix the issue
the remove the update_load param from the update_load param() function
and call reweight_task() only if the task flag doesn't have the
TASK_NEW flag set.

Fixes: 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220203161846.1160750-1-tadeusz.struk@linaro.org
2022-02-06 22:37:26 +01:00
Kevin Hao 53725c4cbd cpufreq: schedutil: Use to_gov_attr_set() to get the gov_attr_set
The to_gov_attr_set() has been moved to the cpufreq.h, so use it to get
the gov_attr_set.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2022-02-04 19:22:34 +01:00
Christoph Hellwig aa8dcccaf3 block: check that there is a plug in blk_flush_plug
Rename blk_flush_plug to __blk_flush_plug and add a wrapper that includes
the NULL check instead of open coding that check everywhere.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220127070549.1377856-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-02 07:50:00 -07:00
Christoph Hellwig b1f866b013 block: remove blk_needs_flush_plug
blk_needs_flush_plug fails to account for the cb_list, which needs
flushing as well.  Remove it and just check if there is a plug instead
of poking into the internals of the plug structure.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220127070549.1377856-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-02-02 07:50:00 -07:00
Zhen Ni c8eaf6ac76 sched: move autogroup sysctls into its own file
move autogroup sysctls to autogroup.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220128095025.8745-1-nizhen@uniontech.com
2022-02-02 13:11:37 +01:00
Linus Torvalds 24f4db1f3a - Make sure the membarrier-rseq fence commands are part of the reported
set when querying membarrier(2) commands through MEMBARRIER_CMD_QUERY
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Merge tag 'sched_urgent_for_v5.17_rc2_p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fix from Borislav Petkov:
 "Make sure the membarrier-rseq fence commands are part of the reported
  set when querying membarrier(2) commands through MEMBARRIER_CMD_QUERY"

* tag 'sched_urgent_for_v5.17_rc2_p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/membarrier: Fix membarrier-rseq fence command missing from query bitmask
2022-01-30 13:09:00 +02:00
Suren Baghdasaryan 44585f7bc0 psi: fix "defined but not used" warnings when CONFIG_PROC_FS=n
When CONFIG_PROC_FS is disabled psi code generates the following
warnings:

  kernel/sched/psi.c:1364:30: warning: 'psi_cpu_proc_ops' defined but not used [-Wunused-const-variable=]
      1364 | static const struct proc_ops psi_cpu_proc_ops = {
           |                              ^~~~~~~~~~~~~~~~
  kernel/sched/psi.c:1355:30: warning: 'psi_memory_proc_ops' defined but not used [-Wunused-const-variable=]
      1355 | static const struct proc_ops psi_memory_proc_ops = {
           |                              ^~~~~~~~~~~~~~~~~~~
  kernel/sched/psi.c:1346:30: warning: 'psi_io_proc_ops' defined but not used [-Wunused-const-variable=]
      1346 | static const struct proc_ops psi_io_proc_ops = {
           |                              ^~~~~~~~~~~~~~~

Make definitions of these structures and related functions conditional
on CONFIG_PROC_FS config.

Link: https://lkml.kernel.org/r/20220119223940.787748-3-surenb@google.com
Fixes: 0e94682b73 ("psi: introduce psi monitor")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-30 09:56:58 +02:00
Suren Baghdasaryan 5102bb1c9f psi: Fix "defined but not used" warnings when CONFIG_PROC_FS=n
When CONFIG_PROC_FS is disabled psi code generates the following warnings:

kernel/sched/psi.c:1364:30: warning: 'psi_cpu_proc_ops' defined but not used [-Wunused-const-variable=]
    1364 | static const struct proc_ops psi_cpu_proc_ops = {
         |                              ^~~~~~~~~~~~~~~~
kernel/sched/psi.c:1355:30: warning: 'psi_memory_proc_ops' defined but not used [-Wunused-const-variable=]
    1355 | static const struct proc_ops psi_memory_proc_ops = {
         |                              ^~~~~~~~~~~~~~~~~~~
kernel/sched/psi.c:1346:30: warning: 'psi_io_proc_ops' defined but not used [-Wunused-const-variable=]
    1346 | static const struct proc_ops psi_io_proc_ops = {
         |                              ^~~~~~~~~~~~~~~

Make definitions of these structures and related functions conditional on
CONFIG_PROC_FS config.

Fixes: 0e94682b73 ("psi: introduce psi monitor")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220119223940.787748-3-surenb@google.com
2022-01-27 12:57:19 +01:00
Qais Yousef d37aee9018 sched/uclamp: Fix iowait boost escaping uclamp restriction
iowait_boost signal is applied independently of util and doesn't take
into account uclamp settings of the rq. An io heavy task that is capped
by uclamp_max could still request higher frequency because
sugov_iowait_apply() doesn't clamp the boost via uclamp_rq_util_with()
like effective_cpu_util() does.

Make sure that iowait_boost honours uclamp requests by calling
uclamp_rq_util_with() when applying the boost.

Fixes: 982d9cdc22 ("sched/cpufreq, sched/uclamp: Add clamps for FAIR and RT tasks")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20211216225320.2957053-3-qais.yousef@arm.com
2022-01-27 12:57:19 +01:00
Qais Yousef 7a17e1db12 sched/sugov: Ignore 'busy' filter when rq is capped by uclamp_max
sugov_update_single_{freq, perf}() contains a 'busy' filter that ensures
we don't bring the frqeuency down if there's no idle time (CPU is busy).

The problem is that with uclamp_max we will have scenarios where a busy
task is capped to run at a lower frequency and this filter prevents
applying the capping when this task starts running.

We handle this by skipping the filter when uclamp is enabled and the rq
is being capped by uclamp_max.

We introduce a new function uclamp_rq_is_capped() to help detecting when
this capping is taking effect. Some code shuffling was required to allow
using cpu_util_{cfs, rt}() in this new function.

On 2 Core SMT2 Intel laptop I see:

Without this patch:

	uclampset -M 0 sysbench --test=cpu --threads = 4 run

produces a score of ~3200 consistently. Which is the highest possible.

Compiling the kernel also results in frequency running at max 3.1GHz all
the time - running uclampset -M 400 to cap it has no effect without this
patch.

With this patch:

	uclampset -M 0 sysbench --test=cpu --threads = 4 run

produces a score of ~1100 with some outliers in ~1700. Uclamp max
aggregates the performance requirements, so having high values sometimes
is expected if some other task happens to require that frequency starts
running at the same time.

When compiling the kernel with uclampset -M 400 I can see the
frequencies mostly in the ~2GHz region. Helpful to conserve power and
prevent heating when not plugged in.

Fixes: 982d9cdc22 ("sched/cpufreq, sched/uclamp: Add clamps for FAIR and RT tasks")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211216225320.2957053-2-qais.yousef@arm.com
2022-01-27 12:57:19 +01:00
Qais Yousef 77cf151b7b sched/core: Export pelt_thermal_tp
We can't use this tracepoint in modules without having the symbol
exported first, fix that.

Fixes: 765047932f ("sched/pelt: Add support to track thermal pressure")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211028115005.873539-1-qais.yousef@arm.com
2022-01-27 12:57:18 +01:00
Honglei Wang 12bf8a7eb8 sched/numa: initialize numa statistics when forking new task
The child processes will inherit numa_pages_migrated and
total_numa_faults from the parent. It means even if there is no numa
fault happen on the child, the statistics in /proc/$pid of the child
process might show huge amount. This is a bit weird. Let's initialize
them when do fork.

Signed-off-by: Honglei Wang <wanghonglei@didichuxing.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20220113133920.49900-1-wanghonglei@didichuxing.com
2022-01-27 12:57:18 +01:00
Bharata B Rao 28c988c3ec sched/debug: Remove mpol_get/put and task_lock/unlock from sched_show_numa
The older format of /proc/pid/sched printed home node info which
required the mempolicy and task lock around mpol_get(). However
the format has changed since then and there is no need for
sched_show_numa() any more to have mempolicy argument,
asssociated mpol_get/put and task_lock/unlock. Remove them.

Fixes: 397f2378f1 ("sched/numa: Fix numa balancing stats in /proc/pid/sched")
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20220118050515.2973-1-bharata@amd.com
2022-01-27 12:57:18 +01:00
Mathieu Desnoyers 809232619f sched/membarrier: Fix membarrier-rseq fence command missing from query bitmask
The membarrier command MEMBARRIER_CMD_QUERY allows querying the
available membarrier commands. When the membarrier-rseq fence commands
were added, a new MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK was
introduced with the intent to expose them with the MEMBARRIER_CMD_QUERY
command, the but it was never added to MEMBARRIER_CMD_BITMASK.

The membarrier-rseq fence commands are therefore not wired up with the
query command.

Rename MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK to
MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK (the bitmask is not a command
per-se), and change the erroneous
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ_BITMASK (which does not
actually exist) to MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ.

Wire up MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK in
MEMBARRIER_CMD_BITMASK. Fixing this allows discovering availability of
the membarrier-rseq fence feature.

Fixes: 2a36ab717e ("rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # 5.10+
Link: https://lkml.kernel.org/r/20220117203010.30129-1-mathieu.desnoyers@efficios.com
2022-01-25 22:30:25 +01:00
Linus Torvalds 10c64a0f28 - A bunch of fixes: forced idle time accounting, utilization values
propagation in the sched hierarchies and other minor cleanups and
 improvements
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Merge tag 'sched_urgent_for_v5.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Borislav Petkov:
 "A bunch of fixes: forced idle time accounting, utilization values
  propagation in the sched hierarchies and other minor cleanups and
  improvements"

* tag 'sched_urgent_for_v5.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kernel/sched: Remove dl_boosted flag comment
  sched: Avoid double preemption in __cond_resched_*lock*()
  sched/fair: Fix all kernel-doc warnings
  sched/core: Accounting forceidle time for all tasks except idle task
  sched/pelt: Relax the sync of load_sum with load_avg
  sched/pelt: Relax the sync of runnable_sum with runnable_avg
  sched/pelt: Continue to relax the sync of util_sum with util_avg
  sched/pelt: Relax the sync of util_sum with util_avg
  psi: Fix uaf issue when psi trigger is destroyed while being polled
2022-01-23 17:35:27 +02:00
Peter Zijlstra 7e406d1ff3 sched: Avoid double preemption in __cond_resched_*lock*()
For PREEMPT/DYNAMIC_PREEMPT the *_unlock() will already trigger a
preemption, no point in then calling preempt_schedule_common()
*again*.

Use _cond_resched() instead, since this is a NOP for the preemptible
configs while it provide a preemption point for the others.

Reported-by: xuhaifeng <xuhaifeng@oppo.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YcGnvDEYBwOiV0cR@hirez.programming.kicks-ass.net
2022-01-18 12:09:59 +01:00
Randy Dunlap a315da5e68 sched/fair: Fix all kernel-doc warnings
Quieten all kernel-doc warnings in kernel/sched/fair.c:

kernel/sched/fair.c:3663: warning: No description found for return value of 'update_cfs_rq_load_avg'
kernel/sched/fair.c:8601: warning: No description found for return value of 'asym_smt_can_pull_tasks'
kernel/sched/fair.c:8673: warning: Function parameter or member 'sds' not described in 'update_sg_lb_stats'
kernel/sched/fair.c:9483: warning: contents before sections

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211218055900.2704-1-rdunlap@infradead.org
2022-01-18 12:09:59 +01:00
Cruz Zhao b171501f25 sched/core: Accounting forceidle time for all tasks except idle task
There are two types of forced idle time: forced idle time from cookie'd
task and forced idle time form uncookie'd task. The forced idle time from
uncookie'd task is actually caused by the cookie'd task in runqueue
indirectly, and it's more accurate to measure the capacity loss with the
sum of both.

Assuming cpu x and cpu y are a pair of SMT siblings, consider the
following scenarios:
  1.There's a cookie'd task running on cpu x, and there're 4 uncookie'd
    tasks running on cpu y. For cpu x, there will be 80% forced idle time
    (from uncookie'd task); for cpu y, there will be 20% forced idle time
    (from cookie'd task).
  2.There's a uncookie'd task running on cpu x, and there're 4 cookie'd
    tasks running on cpu y. For cpu x, there will be 80% forced idle time
    (from cookie'd task); for cpu y, there will be 20% forced idle time
    (from uncookie'd task).

The scenario1 can recurrent by stress-ng(scenario2 can recurrent similary):
    (cookie'd)taskset -c x stress-ng -c 1 -l 100
    (uncookie'd)taskset -c y stress-ng -c 4 -l 100

In the above two scenarios, the total capacity loss is 1 cpu, but in
scenario1, the cookie'd forced idle time tells us 20% cpu capacity loss, in
scenario2, the cookie'd forced idle time tells us 80% cpu capacity loss,
which are not accurate. It'll be more accurate to measure with cookie'd
forced idle time and uncookie'd forced idle time.

Signed-off-by: Cruz Zhao <CruzZhao@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Don <joshdon@google.com>
Link: https://lore.kernel.org/r/1641894961-9241-2-git-send-email-CruzZhao@linux.alibaba.com
2022-01-18 12:09:59 +01:00
Vincent Guittot 2d02fa8cc2 sched/pelt: Relax the sync of load_sum with load_avg
Similarly to util_avg and util_sum, don't sync load_sum with the low
bound of load_avg but only ensure that load_sum stays in the correct range.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-5-vincent.guittot@linaro.org
2022-01-18 12:09:58 +01:00
Vincent Guittot 95246d1ec8 sched/pelt: Relax the sync of runnable_sum with runnable_avg
Similarly to util_avg and util_sum, don't sync runnable_sum with the low
bound of runnable_avg but only ensure that runnable_sum stays in the
correct range.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-4-vincent.guittot@linaro.org
2022-01-18 12:09:58 +01:00
Vincent Guittot 7ceb771030 sched/pelt: Continue to relax the sync of util_sum with util_avg
Rick reported performance regressions in bugzilla because of cpu frequency
being lower than before:
    https://bugzilla.kernel.org/show_bug.cgi?id=215045

He bisected the problem to:
commit 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")

This commit forces util_sum to be synced with the new util_avg after
removing the contribution of a task and before the next periodic sync. By
doing so util_sum is rounded to its lower bound and might lost up to
LOAD_AVG_MAX-1 of accumulated contribution which has not yet been
reflected in util_avg.

update_tg_cfs_util() is not the only place where we round util_sum and
lost some accumulated contributions that are not already reflected in
util_avg. Modify update_tg_cfs_util() and detach_entity_load_avg() to not
sync util_sum with the new util_avg. Instead of always setting util_sum to
the low bound of util_avg, which can significantly lower the utilization,
we propagate the difference. In addition, we also check that cfs's util_sum
always stays above the lower bound for a given util_avg as it has been
observed that sched_entity's util_sum is sometimes above cfs one.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-3-vincent.guittot@linaro.org
2022-01-18 12:09:58 +01:00
Vincent Guittot 98b0d89022 sched/pelt: Relax the sync of util_sum with util_avg
Rick reported performance regressions in bugzilla because of cpu frequency
being lower than before:
    https://bugzilla.kernel.org/show_bug.cgi?id=215045

He bisected the problem to:
commit 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")

This commit forces util_sum to be synced with the new util_avg after
removing the contribution of a task and before the next periodic sync. By
doing so util_sum is rounded to its lower bound and might lost up to
LOAD_AVG_MAX-1 of accumulated contribution which has not yet been
reflected in util_avg.

Instead of always setting util_sum to the low bound of util_avg, which can
significantly lower the utilization of root cfs_rq after propagating the
change down into the hierarchy, we revert the change of util_sum and
propagate the difference.

In addition, we also check that cfs's util_sum always stays above the
lower bound for a given util_avg as it has been observed that
sched_entity's util_sum is sometimes above cfs one.

Fixes: 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")
Reported-by: Rick Yiu <rickyiu@google.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-2-vincent.guittot@linaro.org
2022-01-18 12:09:58 +01:00
Suren Baghdasaryan a06247c680 psi: Fix uaf issue when psi trigger is destroyed while being polled
With write operation on psi files replacing old trigger with a new one,
the lifetime of its waitqueue is totally arbitrary. Overwriting an
existing trigger causes its waitqueue to be freed and pending poll()
will stumble on trigger->event_wait which was destroyed.
Fix this by disallowing to redefine an existing psi trigger. If a write
operation is used on a file descriptor with an already existing psi
trigger, the operation will fail with EBUSY error.
Also bypass a check for psi_disabled in the psi_trigger_destroy as the
flag can be flipped after the trigger is created, leading to a memory
leak.

Fixes: 0e94682b73 ("psi: introduce psi monitor")
Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Analyzed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com
2022-01-18 12:09:57 +01:00
Linus Torvalds 35ce8ae9ae Merge branch 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull signal/exit/ptrace updates from Eric Biederman:
 "This set of changes deletes some dead code, makes a lot of cleanups
  which hopefully make the code easier to follow, and fixes bugs found
  along the way.

  The end-game which I have not yet reached yet is for fatal signals
  that generate coredumps to be short-circuit deliverable from
  complete_signal, for force_siginfo_to_task not to require changing
  userspace configured signal delivery state, and for the ptrace stops
  to always happen in locations where we can guarantee on all
  architectures that the all of the registers are saved and available on
  the stack.

  Removal of profile_task_ext, profile_munmap, and profile_handoff_task
  are the big successes for dead code removal this round.

  A bunch of small bug fixes are included, as most of the issues
  reported were small enough that they would not affect bisection so I
  simply added the fixes and did not fold the fixes into the changes
  they were fixing.

  There was a bug that broke coredumps piped to systemd-coredump. I
  dropped the change that caused that bug and replaced it entirely with
  something much more restrained. Unfortunately that required some
  rebasing.

  Some successes after this set of changes: There are few enough calls
  to do_exit to audit in a reasonable amount of time. The lifetime of
  struct kthread now matches the lifetime of struct task, and the
  pointer to struct kthread is no longer stored in set_child_tid. The
  flag SIGNAL_GROUP_COREDUMP is removed. The field group_exit_task is
  removed. Issues where task->exit_code was examined with
  signal->group_exit_code should been examined were fixed.

  There are several loosely related changes included because I am
  cleaning up and if I don't include them they will probably get lost.

  The original postings of these changes can be found at:
     https://lkml.kernel.org/r/87a6ha4zsd.fsf@email.froward.int.ebiederm.org
     https://lkml.kernel.org/r/87bl1kunjj.fsf@email.froward.int.ebiederm.org
     https://lkml.kernel.org/r/87r19opkx1.fsf_-_@email.froward.int.ebiederm.org

  I trimmed back the last set of changes to only the obviously correct
  once. Simply because there was less time for review than I had hoped"

* 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (44 commits)
  ptrace/m68k: Stop open coding ptrace_report_syscall
  ptrace: Remove unused regs argument from ptrace_report_syscall
  ptrace: Remove second setting of PT_SEIZED in ptrace_attach
  taskstats: Cleanup the use of task->exit_code
  exit: Use the correct exit_code in /proc/<pid>/stat
  exit: Fix the exit_code for wait_task_zombie
  exit: Coredumps reach do_group_exit
  exit: Remove profile_handoff_task
  exit: Remove profile_task_exit & profile_munmap
  signal: clean up kernel-doc comments
  signal: Remove the helper signal_group_exit
  signal: Rename group_exit_task group_exec_task
  coredump: Stop setting signal->group_exit_task
  signal: Remove SIGNAL_GROUP_COREDUMP
  signal: During coredumps set SIGNAL_GROUP_EXIT in zap_process
  signal: Make coredump handling explicit in complete_signal
  signal: Have prepare_signal detect coredumps using signal->core_state
  signal: Have the oom killer detect coredumps using signal->core_state
  exit: Move force_uaccess back into do_exit
  exit: Guarantee make_task_dead leaks the tsk when calling do_task_exit
  ...
2022-01-17 05:49:30 +02:00
Linus Torvalds daadb3bd0e Peter Zijlstra says:
"Lots of cleanups and preparation; highlights:
 
  - futex: Cleanup and remove runtime futex_cmpxchg detection
 
  - rtmutex: Some fixes for the PREEMPT_RT locking infrastructure
 
  - kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and
    annotate the racy owner->on_cpu access *once*.
 
  - atomic64: Dead-Code-Elemination"
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Merge tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Borislav Petkov:
 "Lots of cleanups and preparation. Highlights:

   - futex: Cleanup and remove runtime futex_cmpxchg detection

   - rtmutex: Some fixes for the PREEMPT_RT locking infrastructure

   - kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and
     annotate the racy owner->on_cpu access *once*.

   - atomic64: Dead-Code-Elemination"

[ Description above by Peter Zijlstra ]

* tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/atomic: atomic64: Remove unusable atomic ops
  futex: Fix additional regressions
  locking: Allow to include asm/spinlock_types.h from linux/spinlock_types_raw.h
  x86/mm: Include spinlock_t definition in pgtable.
  locking: Mark racy reads of owner->on_cpu
  locking: Make owner_on_cpu() into <linux/sched.h>
  lockdep/selftests: Adapt ww-tests for PREEMPT_RT
  lockdep/selftests: Skip the softirq related tests on PREEMPT_RT
  lockdep/selftests: Unbalanced migrate_disable() & rcu_read_lock().
  lockdep/selftests: Avoid using local_lock_{acquire|release}().
  lockdep: Remove softirq accounting on PREEMPT_RT.
  locking/rtmutex: Add rt_mutex_lock_nest_lock() and rt_mutex_lock_killable().
  locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.
  locking: Remove rt_rwlock_is_contended().
  sched: Trigger warning if ->migration_disabled counter underflows.
  futex: Fix sparc32/m68k/nds32 build regression
  futex: Remove futex_cmpxchg detection
  futex: Ensure futex_atomic_cmpxchg_inatomic() is present
  kernel/locking: Use a pointer in ww_mutex_trylock().
2022-01-11 17:24:45 -08:00
Linus Torvalds 6ae71436cd Peter Zijlstra says:
"Mostly minor things this time; some highlights:
 
  - core-sched: Add 'Forced Idle' accounting; this allows to track how
    much CPU time is 'lost' due to core scheduling constraints.
 
  - psi: Fix for MEM_FULL; a task running reclaim would be counted as a
    runnable task and prevent MEM_FULL from being reported.
 
  - cpuacct: Long standing fixes for some cgroup accounting issues.
 
  - rt: Bandwidth timer could, under unusual circumstances, be failed to
    armed, leading to indefinite throttling."
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Merge tag 'sched_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Borislav Petkov:
 "Mostly minor things this time; some highlights:

   - core-sched: Add 'Forced Idle' accounting; this allows to track how
     much CPU time is 'lost' due to core scheduling constraints.

   - psi: Fix for MEM_FULL; a task running reclaim would be counted as a
     runnable task and prevent MEM_FULL from being reported.

   - cpuacct: Long standing fixes for some cgroup accounting issues.

   - rt: Bandwidth timer could, under unusual circumstances, be failed
     to armed, leading to indefinite throttling."

[ Description above by Peter Zijlstra ]

* tag 'sched_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Replace CFS internal cpu_util() with cpu_util_cfs()
  sched/fair: Cleanup task_util and capacity type
  sched/rt: Try to restart rt period timer when rt runtime exceeded
  sched/fair: Document the slow path and fast path in select_task_rq_fair
  sched/fair: Fix per-CPU kthread and wakee stacking for asym CPU capacity
  sched/fair: Fix detection of per-CPU kthreads waking a task
  sched/cpuacct: Make user/system times in cpuacct.stat more precise
  sched/cpuacct: Fix user/system in shown cpuacct.usage*
  cpuacct: Convert BUG_ON() to WARN_ON_ONCE()
  cputime, cpuacct: Include guest time in user time in cpuacct.stat
  psi: Fix PSI_MEM_FULL state when tasks are in memstall and doing reclaim
  sched/core: Forced idle accounting
  psi: Add a missing SPDX license header
  psi: Remove repeated verbose comment
2022-01-11 17:14:59 -08:00
Linus Torvalds 1be5bdf8cd KCSAN updates for v5.17
This series provides KCSAN fixes and also the ability to take memory
 barriers into account for weakly-ordered systems.  This last can increase
 the probability of detecting certain types of data races.
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Merge tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull KCSAN updates from Paul McKenney:
 "This provides KCSAN fixes and also the ability to take memory barriers
  into account for weakly-ordered systems. This last can increase the
  probability of detecting certain types of data races"

* tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (29 commits)
  kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it
  kcsan: Avoid nested contexts reading inconsistent reorder_access
  kcsan: Turn barrier instrumentation into macros
  kcsan: Make barrier tests compatible with lockdep
  kcsan: Support WEAK_MEMORY with Clang where no objtool support exists
  compiler_attributes.h: Add __disable_sanitizer_instrumentation
  objtool, kcsan: Remove memory barrier instrumentation from noinstr
  objtool, kcsan: Add memory barrier instrumentation to whitelist
  sched, kcsan: Enable memory barrier instrumentation
  mm, kcsan: Enable barrier instrumentation
  x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock()
  x86/barriers, kcsan: Use generic instrumentation for non-smp barriers
  asm-generic/bitops, kcsan: Add instrumentation for barriers
  locking/atomics, kcsan: Add instrumentation for barriers
  locking/barriers, kcsan: Support generic instrumentation
  locking/barriers, kcsan: Add instrumentation for barriers
  kcsan: selftest: Add test case to check memory barrier instrumentation
  kcsan: Ignore GCC 11+ warnings about TSan runtime support
  kcsan: test: Add test cases for memory barrier instrumentation
  kcsan: test: Match reordered or normal accesses
  ...
2022-01-11 09:51:26 -08:00
Linus Torvalds 48a60bdb2b - Add a set of thread_info.flags accessors which snapshot it before
accesing it in order to prevent any potential data races, and convert
 all users to those new accessors
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Merge tag 'core_entry_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull thread_info flag accessor helper updates from Borislav Petkov:
 "Add a set of thread_info.flags accessors which snapshot it before
  accesing it in order to prevent any potential data races, and convert
  all users to those new accessors"

* tag 'core_entry_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  powerpc: Snapshot thread flags
  powerpc: Avoid discarding flags in system_call_exception()
  openrisc: Snapshot thread flags
  microblaze: Snapshot thread flags
  arm64: Snapshot thread flags
  ARM: Snapshot thread flags
  alpha: Snapshot thread flags
  sched: Snapshot thread flags
  entry: Snapshot thread flags
  x86: Snapshot thread flags
  thread_info: Add helpers to snapshot thread flags
2022-01-10 11:34:10 -08:00
Eric W. Biederman e32cf5dfbe kthread: Generalize pf_io_worker so it can point to struct kthread
The point of using set_child_tid to hold the kthread pointer was that
it already did what is necessary.  There are now restrictions on when
set_child_tid can be initialized and when set_child_tid can be used in
schedule_tail.  Which indicates that continuing to use set_child_tid
to hold the kthread pointer is a bad idea.

Instead of continuing to use the set_child_tid field of task_struct
generalize the pf_io_worker field of task_struct and use it to hold
the kthread pointer.

Rename pf_io_worker (which is a void * pointer) to worker_private so
it can be used to store kthreads struct kthread pointer.  Update the
kthread code to store the kthread pointer in the worker_private field.
Remove the places where set_child_tid had to be dealt with carefully
because kthreads also used it.

Link: https://lkml.kernel.org/r/CAHk-=wgtFAA9SbVYg0gR1tqPMC17-NYcs0GQkaYg1bGhh1uJQQ@mail.gmail.com
Link: https://lkml.kernel.org/r/87a6grvqy8.fsf_-_@email.froward.int.ebiederm.org
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-01-08 09:39:49 -06:00
Eric W. Biederman 00580f03af kthread: Never put_user the set_child_tid address
Kernel threads abuse set_child_tid.  Historically that has been fine
as set_child_tid was initialized after the kernel thread had been
forked.  Unfortunately storing struct kthread in set_child_tid after
the thread is running makes struct kthread being unusable for storing
result codes of the thread.

When set_child_tid is set to struct kthread during fork that results
in schedule_tail writing the thread id to the beggining of struct
kthread (if put_user does not realize it is a kernel address).

Solve this by skipping the put_user for all kthreads.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YcNsG0Lp94V13whH@archlinux-ax161
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-12-22 16:57:50 -06:00
Eric W. Biederman dd621ee0cf kthread: Warn about failed allocations for the init kthread
Failed allocates are not expected when setting up the initial task and
it is not really possible to handle them either.  So I added a warning
to report if such an allocation failure ever happens.

Correct the sense of the warning so it warns when an allocation failure
happens not when the allocation succeeded.  Oops.

Reported-by: kernel test robot <oliver.sang@intel.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Link: https://lkml.kernel.org/r/20211221231611.785b74cf@canb.auug.org.au
Link: https://lkml.kernel.org/r/CA+G9fYvLaR5CF777CKeWTO+qJFTN6vAvm95gtzN+7fw3Wi5hkA@mail.gmail.com
Link: https://lkml.kernel.org/r/20211216102956.GC10708@xsang-OptiPlex-9020
Fixes: 40966e316f ("kthread: Ensure struct kthread is present for all kthreads")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-12-21 16:20:51 -06:00
Eric W. Biederman 40966e316f kthread: Ensure struct kthread is present for all kthreads
Today the rules are a bit iffy and arbitrary about which kernel
threads have struct kthread present.  Both idle threads and thread
started with create_kthread want struct kthread present so that is
effectively all kernel threads.  Make the rule that if PF_KTHREAD
and the task is running then struct kthread is present.

This will allow the kernel thread code to using tsk->exit_code
with different semantics from ordinary processes.

To make ensure that struct kthread is present for all
kernel threads move it's allocation into copy_process.

Add a deallocation of struct kthread in exec for processes
that were kernel threads.

Move the allocation of struct kthread for the initial thread
earlier so that it is not repeated for each additional idle
thread.

Move the initialization of struct kthread into set_kthread_struct
so that the structure is always and reliably initailized.

Clear set_child_tid in free_kthread_struct to ensure the kthread
struct is reliably freed during exec.  The function
free_kthread_struct does not need to clear vfork_done during exec as
exec_mm_release called from exec_mmap has already cleared vfork_done.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-12-13 12:04:45 -06:00
Ingo Molnar 6773cc31a9 Linux 5.16-rc5
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Merge tag 'v5.16-rc5' into locking/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2021-12-13 10:48:46 +01:00
Dietmar Eggemann 82762d2af3 sched/fair: Replace CFS internal cpu_util() with cpu_util_cfs()
cpu_util_cfs() was created by commit d4edd662ac ("sched/cpufreq: Use
the DEADLINE utilization signal") to enable the access to CPU
utilization from the Schedutil CPUfreq governor.

Commit a07630b8b2 ("sched/cpufreq/schedutil: Use util_est for OPP
selection") added util_est support later.

The only thing cpu_util() is doing on top of what cpu_util_cfs() already
does is to clamp the return value to the [0..capacity_orig] capacity
range of the CPU. Integrating this into cpu_util_cfs() is not harming
the existing users (Schedutil and CPUfreq cooling (latter via
sched_cpu_util() wrapper)).

For straightforwardness, prefer to keep using `int cpu` as the function
parameter over using `struct rq *rq` which might avoid some calls to
cpu_rq(cpu) -> per_cpu(runqueues, cpu) -> RELOC_HIDE().
Update cfs_util()'s documentation and reuse it for cpu_util_cfs().
Remove cpu_util().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211118164240.623551-1-dietmar.eggemann@arm.com
2021-12-11 09:10:00 +01:00
Marco Elver 6f3f0c98b5 sched, kcsan: Enable memory barrier instrumentation
There's no fundamental reason to disable KCSAN for scheduler code,
except for excessive noise and performance concerns (instrumenting
scheduler code is usually a good way to stress test KCSAN itself).

However, several core sched functions imply memory barriers that are
invisible to KCSAN without instrumentation, but are required to avoid
false positives. Therefore, unconditionally enable instrumentation of
memory barriers in scheduler code. Also update the comment to reflect
this and be a bit more brief.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-12-09 16:42:28 -08:00
Eric Biggers 42288cb44c wait: add wake_up_pollfree()
Several ->poll() implementations are special in that they use a
waitqueue whose lifetime is the current task, rather than the struct
file as is normally the case.  This is okay for blocking polls, since a
blocking poll occurs within one task; however, non-blocking polls
require another solution.  This solution is for the queue to be cleared
before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'.

However, that has a bug: wake_up_poll() calls __wake_up() with
nr_exclusive=1.  Therefore, if there are multiple "exclusive" waiters,
and the wakeup function for the first one returns a positive value, only
that one will be called.  That's *not* what's needed for POLLFREE;
POLLFREE is special in that it really needs to wake up everyone.

Considering the three non-blocking poll systems:

- io_uring poll doesn't handle POLLFREE at all, so it is broken anyway.

- aio poll is unaffected, since it doesn't support exclusive waits.
  However, that's fragile, as someone could add this feature later.

- epoll doesn't appear to be broken by this, since its wakeup function
  returns 0 when it sees POLLFREE.  But this is fragile.

Although there is a workaround (see epoll), it's better to define a
function which always sends POLLFREE to all waiters.  Add such a
function.  Also make it verify that the queue really becomes empty after
all waiters have been woken up.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
2021-12-09 10:49:56 -08:00
Vincent Donnefort ef8df9798d sched/fair: Cleanup task_util and capacity type
task_util and capacity are comparable unsigned long values. There is no
need for an intermidiate implicit signed cast.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211207095755.859972-1-vincent.donnefort@arm.com
2021-12-08 22:22:02 +01:00
Li Hua 9b58e976b3 sched/rt: Try to restart rt period timer when rt runtime exceeded
When rt_runtime is modified from -1 to a valid control value, it may
cause the task to be throttled all the time. Operations like the following
will trigger the bug. E.g:

  1. echo -1 > /proc/sys/kernel/sched_rt_runtime_us
  2. Run a FIFO task named A that executes while(1)
  3. echo 950000 > /proc/sys/kernel/sched_rt_runtime_us

When rt_runtime is -1, The rt period timer will not be activated when task
A enqueued. And then the task will be throttled after setting rt_runtime to
950,000. The task will always be throttled because the rt period timer is
not activated.

Fixes: d0b27fa778 ("sched: rt-group: synchonised bandwidth period")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Li Hua <hucool.lihua@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211203033618.11895-1-hucool.lihua@huawei.com
2021-12-07 15:14:10 +01:00
Barry Song 2917406c35 sched/fair: Document the slow path and fast path in select_task_rq_fair
All People I know including myself took a long time to figure out that
typical wakeup will always go to fast path and never go to slow path
except WF_FORK and WF_EXEC.

Vincent reminded me once in a linaro meeting and made me understand
slow path won't happen for WF_TTWU. But my other friends repeatedly
wasted a lot of time on testing this path like me before I reminded
them.

So obviously the code needs some document.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211016111109.5559-1-21cnbao@gmail.com
2021-12-07 15:14:10 +01:00
Sebastian Andrzej Siewior 9d0df37797 sched: Trigger warning if ->migration_disabled counter underflows.
If migrate_enable() is used more often than its counter part then it
remains undetected and rq::nr_pinned will underflow, too.

Add a warning if migrate_enable() is attempted if without a matching a
migrate_disable().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-2-bigeasy@linutronix.de
2021-12-04 10:56:22 +01:00
Vincent Donnefort 014ba44e81 sched/fair: Fix per-CPU kthread and wakee stacking for asym CPU capacity
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread where the selected CPU is the previous one. For asymmetric CPU
capacity systems, the assumption was that the wakee couldn't have a
bigger utilization during task placement than it used to have during the
last activation. That was not considering uclamp.min which can completely
change between two task activations and as a consequence mandates the
fitness criterion asym_fits_capacity(), even for the exit path described
above.

Fixes: b4c9c9f156 ("sched/fair: Prefer prev cpu in asymmetric wakeup path")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211129173115.4006346-1-vincent.donnefort@arm.com
2021-12-04 10:56:21 +01:00
Vincent Donnefort 8b4e74ccb5 sched/fair: Fix detection of per-CPU kthreads waking a task
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread, where the selected CPU is the previous one. However, the current
condition for this exit path is incomplete. A task can wake up from an
interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A
such scenario would spuriously trigger the special case described above.
Also, a recent change made the idle task like a regular per-CPU kthread,
hence making that situation more likely to happen
(is_per_cpu_kthread(swapper) being true now).

Checking for task context makes sure select_idle_sibling() will not
interpret a wake up from any other context as a wake up by a per-CPU
kthread.

Fixes: 52262ee567 ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com
2021-12-04 10:56:20 +01:00
Qais Yousef 315c4f8848 sched/uclamp: Fix rq->uclamp_max not set on first enqueue
Commit d81ae8aac8 ("sched/uclamp: Fix initialization of struct
uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to
match the woken up task's uclamp_max when the rq is idle.

The code was relying on rq->uclamp_max initialized to zero, so on first
enqueue

	static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
					    enum uclamp_id clamp_id)
	{
		...

		if (uc_se->value > READ_ONCE(uc_rq->value))
			WRITE_ONCE(uc_rq->value, uc_se->value);
	}

was actually resetting it. But since commit d81ae8aac8 changed the
default to 1024, this no longer works. And since rq->uclamp_flags is
also initialized to 0, neither above code path nor uclamp_idle_reset()
update the rq->uclamp_max on first wake up from idle.

This is only visible from first wake up(s) until the first dequeue to
idle after enabling the static key. And it only matters if the
uclamp_max of this task is < 1024 since only then its uclamp_max will be
effectively ignored.

Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to
ensure uclamp_idle_reset() is called which then will update the rq
uclamp_max value as expected.

Fixes: d81ae8aac8 ("sched/uclamp: Fix initialization of struct uclamp_rq")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com
2021-12-04 10:56:18 +01:00
Andrew Halaney 9ed20bafc8 preempt/dynamic: Fix setup_preempt_mode() return value
__setup() callbacks expect 1 for success and 0 for failure. Correct the
usage here to reflect that.

Fixes: 826bfeb37b ("preempt/dynamic: Support dynamic preempt with preempt= boot option")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211203233203.133581-1-ahalaney@redhat.com
2021-12-04 10:56:18 +01:00
Frederic Weisbecker e7f2be115f sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime
than the actual time.

task_cputime_adjusted() snapshots utime and stime and then adjust their
sum to match the scheduler maintained cputime.sum_exec_runtime.
Unfortunately in nohz_full, sum_exec_runtime is only updated once per
second in the worst case, causing a discrepancy against utime and stime
that can be updated anytime by the reader using vtime.

To fix this situation, perform an update of cputime.sum_exec_runtime
when the cputime snapshot reports the task as actually running while
the tick is disabled. The related overhead is then contained within the
relevant situations.

Reported-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
2021-12-02 15:08:22 +01:00
Mark Rutland 0569b24513 sched: Snapshot thread flags
Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.

To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.

Convert them all to the new flag accessor helpers.

The READ_ONCE(ti->flags) .. cmpxchg(ti->flags) loop in
set_nr_if_polling() is left as-is for clarity.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-4-mark.rutland@arm.com
2021-12-01 00:06:43 +01:00
Mark Rutland dce1ca0525 sched/scs: Reset task stack state in bringup_cpu()
To hot unplug a CPU, the idle task on that CPU calls a few layers of C
code before finally leaving the kernel. When KASAN is in use, poisoned
shadow is left around for each of the active stack frames, and when
shadow call stacks are in use. When shadow call stacks (SCS) are in use
the task's saved SCS SP is left pointing at an arbitrary point within
the task's shadow call stack.

When a CPU is offlined than onlined back into the kernel, this stale
state can adversely affect execution. Stale KASAN shadow can alias new
stackframes and result in bogus KASAN warnings. A stale SCS SP is
effectively a memory leak, and prevents a portion of the shadow call
stack being used. Across a number of hotplug cycles the idle task's
entire shadow call stack can become unusable.

We previously fixed the KASAN issue in commit:

  e1b77c9298 ("sched/kasan: remove stale KASAN poison after hotplug")

... by removing any stale KASAN stack poison immediately prior to
onlining a CPU.

Subsequently in commit:

  f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")

... the refactoring left the KASAN and SCS cleanup in one-time idle
thread initialization code rather than something invoked prior to each
CPU being onlined, breaking both as above.

We fixed SCS (but not KASAN) in commit:

  63acd42c0d ("sched/scs: Reset the shadow stack when idle_task_exit")

... but as this runs in the context of the idle task being offlined it's
potentially fragile.

To fix these consistently and more robustly, reset the SCS SP and KASAN
shadow of a CPU's idle task immediately before we online that CPU in
bringup_cpu(). This ensures the idle task always has a consistent state
when it is running, and removes the need to so so when exiting an idle
task.

Whenever any thread is created, dup_task_struct() will give the task a
stack which is free of KASAN shadow, and initialize the task's SCS SP,
so there's no need to specially initialize either for idle thread within
init_idle(), as this was only necessary to handle hotplug cycles.

I've tested this on arm64 with:

* gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK
* clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK

... offlining and onlining CPUS with:

| while true; do
|   for C in /sys/devices/system/cpu/cpu*/online; do
|     echo 0 > $C;
|     echo 1 > $C;
|   done
| done

Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Link: https://lore.kernel.org/lkml/20211115113310.35693-1-mark.rutland@arm.com/
2021-11-24 12:20:27 +01:00
Andrey Ryabinin 8c92606ab8 sched/cpuacct: Make user/system times in cpuacct.stat more precise
cpuacct.stat shows user time based on raw random precision tick
based counters. Use cputime_addjust() to scale these values against the
total runtime accounted by the scheduler, like we already do
for user/system times in /proc/<pid>/stat.

Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-4-arbn@yandex-team.com
2021-11-23 09:55:22 +01:00
Andrey Ryabinin dd02d4234c sched/cpuacct: Fix user/system in shown cpuacct.usage*
cpuacct has 2 different ways of accounting and showing user
and system times.

The first one uses cpuacct_account_field() to account times
and cpuacct.stat file to expose them. And this one seems to work ok.

The second one is uses cpuacct_charge() function for accounting and
set of cpuacct.usage* files to show times. Despite some attempts to
fix it in the past it still doesn't work. Sometimes while running KVM
guest the cpuacct_charge() accounts most of the guest time as
system time. This doesn't match with user&system times shown in
cpuacct.stat or proc/<pid>/stat.

Demonstration:
 # git clone https://github.com/aryabinin/kvmsample
 # make
 # mkdir /sys/fs/cgroup/cpuacct/test
 # echo $$ > /sys/fs/cgroup/cpuacct/test/tasks
 # ./kvmsample &
 # for i in {1..5}; do cat /sys/fs/cgroup/cpuacct/test/cpuacct.usage_sys; sleep 1; done
 1976535645
 2979839428
 3979832704
 4983603153
 5983604157

Use cpustats accounted in cpuacct_account_field() as the source
of user/sys times for cpuacct.usage* files. Make cpuacct_charge()
to account only summary execution time.

Fixes: d740037fac ("sched/cpuacct: Split usage accounting into user_usage and sys_usage")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-3-arbn@yandex-team.com
2021-11-23 09:55:22 +01:00
Andrey Ryabinin c7ccbf4b61 cpuacct: Convert BUG_ON() to WARN_ON_ONCE()
Replace fatal BUG_ON() with more safe WARN_ON_ONCE() in cpuacct_cpuusage_read().

Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-2-arbn@yandex-team.com
2021-11-23 09:55:22 +01:00
Andrey Ryabinin 9731698ecb cputime, cpuacct: Include guest time in user time in cpuacct.stat
cpuacct.stat in no-root cgroups shows user time without guest time
included int it. This doesn't match with user time shown in root
cpuacct.stat and /proc/<pid>/stat. This also affects cgroup2's cpu.stat
in the same way.

Make account_guest_time() to add user time to cgroup's cpustat to
fix this.

Fixes: ef12fefabf ("cpuacct: add per-cgroup utime/stime statistics")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-1-arbn@yandex-team.com
2021-11-23 09:55:22 +01:00
Brian Chen cb0e52b774 psi: Fix PSI_MEM_FULL state when tasks are in memstall and doing reclaim
We've noticed cases where tasks in a cgroup are stalled on memory but
there is little memory FULL pressure since tasks stay on the runqueue
in reclaim.

A simple example involves a single threaded program that keeps leaking
and touching large amounts of memory. It runs in a cgroup with swap
enabled, memory.high set at 10M and cpu.max ratio set at 5%. Though
there is significant CPU pressure and memory SOME, there is barely any
memory FULL since the task enters reclaim and stays on the runqueue.
However, this memory-bound task is effectively stalled on memory and
we expect memory FULL to match memory SOME in this scenario.

The code is confused about memstall && running, thinking there is a
stalled task and a productive task when there's only one task: a
reclaimer that's counted as both. To fix this, we redefine the
condition for PSI_MEM_FULL to check that all running tasks are in an
active memstall instead of checking that there are no running tasks.

        case PSI_MEM_FULL:
-               return unlikely(tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]);
+               return unlikely(tasks[NR_MEMSTALL] &&
+                       tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]);

This will capture reclaimers. It will also capture tasks that called
psi_memstall_enter() and are about to sleep, but this should be
negligible noise.

Signed-off-by: Brian Chen <brianchen118@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20211110213312.310243-1-brianchen118@gmail.com
2021-11-17 14:49:00 +01:00
Josh Don 4feee7d126 sched/core: Forced idle accounting
Adds accounting for "forced idle" time, which is time where a cookie'd
task forces its SMT sibling to idle, despite the presence of runnable
tasks.

Forced idle time is one means to measure the cost of enabling core
scheduling (ie. the capacity lost due to the need to force idle).

Forced idle time is attributed to the thread responsible for causing
the forced idle.

A few details:
 - Forced idle time is displayed via /proc/PID/sched. It also requires
   that schedstats is enabled.
 - Forced idle is only accounted when a sibling hyperthread is held
   idle despite the presence of runnable tasks. No time is charged if
   a sibling is idle but has no runnable tasks.
 - Tasks with 0 cookie are never charged forced idle.
 - For SMT > 2, we scale the amount of forced idle charged based on the
   number of forced idle siblings. Additionally, we split the time up and
   evenly charge it to all running tasks, as each is equally responsible
   for the forced idle.

Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211018203428.2025792-1-joshdon@google.com
2021-11-17 14:49:00 +01:00
Liu Xinpeng 2fb75e1b64 psi: Add a missing SPDX license header
Add the missing SPDX license header to
include/linux/psi.h
include/linux/psi_types.h
kernel/sched/psi.c

Signed-off-by: Liu Xinpeng <liuxp11@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/1635133586-84611-2-git-send-email-liuxp11@chinatelecom.cn
2021-11-17 14:48:59 +01:00
Liu Xinpeng 2d3791f116 psi: Remove repeated verbose comment
Comment in function psi_task_switch,there are two same lines.
...
* runtime state, the cgroup that contains both tasks
* runtime state, the cgroup that contains both tasks
...

Signed-off-by: Liu Xinpeng <liuxp11@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/1635133586-84611-1-git-send-email-liuxp11@chinatelecom.cn
2021-11-17 14:48:59 +01:00
Valentin Schneider a8b76910e4 preempt: Restore preemption model selection configs
Commit c597bfddc9 ("sched: Provide Kconfig support for default dynamic
preempt mode") changed the selectable config names for the preemption
model. This means a config file must now select

  CONFIG_PREEMPT_BEHAVIOUR=y

rather than

  CONFIG_PREEMPT=y

to get a preemptible kernel. This means all arch config files would need to
be updated - right now they'll all end up with the default
CONFIG_PREEMPT_NONE_BEHAVIOUR.

Rather than touch a good hundred of config files, restore usage of
CONFIG_PREEMPT{_NONE, _VOLUNTARY}. Make them configure:
o The build-time preemption model when !PREEMPT_DYNAMIC
o The default boot-time preemption model when PREEMPT_DYNAMIC

Add siblings of those configs with the _BUILD suffix to unconditionally
designate the build-time preemption model (PREEMPT_DYNAMIC is built with
the "highest" preemption model it supports, aka PREEMPT). Downstream
configs should by now all be depending / selected by CONFIG_PREEMPTION
rather than CONFIG_PREEMPT, so only a few sites need patching up.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20211110202448.4054153-2-valentin.schneider@arm.com
2021-11-11 13:09:33 +01:00
Mathias Krause b027789e5e sched/fair: Prevent dead task groups from regaining cfs_rq's
Kevin is reporting crashes which point to a use-after-free of a cfs_rq
in update_blocked_averages(). Initial debugging revealed that we've
live cfs_rq's (on_list=1) in an about to be kfree()'d task group in
free_fair_sched_group(). However, it was unclear how that can happen.

His kernel config happened to lead to a layout of struct sched_entity
that put the 'my_q' member directly into the middle of the object
which makes it incidentally overlap with SLUB's freelist pointer.
That, in combination with SLAB_FREELIST_HARDENED's freelist pointer
mangling, leads to a reliable access violation in form of a #GP which
made the UAF fail fast.

Michal seems to have run into the same issue[1]. He already correctly
diagnosed that commit a7b359fc6a ("sched/fair: Correctly insert
cfs_rq's to list on unthrottle") is causing the preconditions for the
UAF to happen by re-adding cfs_rq's also to task groups that have no
more running tasks, i.e. also to dead ones. His analysis, however,
misses the real root cause and it cannot be seen from the crash
backtrace only, as the real offender is tg_unthrottle_up() getting
called via sched_cfs_period_timer() via the timer interrupt at an
inconvenient time.

When unregister_fair_sched_group() unlinks all cfs_rq's from the dying
task group, it doesn't protect itself from getting interrupted. If the
timer interrupt triggers while we iterate over all CPUs or after
unregister_fair_sched_group() has finished but prior to unlinking the
task group, sched_cfs_period_timer() will execute and walk the list of
task groups, trying to unthrottle cfs_rq's, i.e. re-add them to the
dying task group. These will later -- in free_fair_sched_group() -- be
kfree()'ed while still being linked, leading to the fireworks Kevin
and Michal are seeing.

To fix this race, ensure the dying task group gets unlinked first.
However, simply switching the order of unregistering and unlinking the
task group isn't sufficient, as concurrent RCU walkers might still see
it, as can be seen below:

    CPU1:                                      CPU2:
      :                                        timer IRQ:
      :                                          do_sched_cfs_period_timer():
      :                                            :
      :                                            distribute_cfs_runtime():
      :                                              rcu_read_lock();
      :                                              :
      :                                              unthrottle_cfs_rq():
    sched_offline_group():                             :
      :                                                walk_tg_tree_from(…,tg_unthrottle_up,…):
      list_del_rcu(&tg->list);                           :
 (1)  :                                                  list_for_each_entry_rcu(child, &parent->children, siblings)
      :                                                    :
 (2)  list_del_rcu(&tg->siblings);                         :
      :                                                    tg_unthrottle_up():
      unregister_fair_sched_group():                         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
        :                                                    :
        list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);               :
        :                                                    :
        :                                                    if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
 (3)    :                                                        list_add_leaf_cfs_rq(cfs_rq);
      :                                                      :
      :                                                    :
      :                                                  :
      :                                                :
      :                                              :
 (4)  :                                              rcu_read_unlock();

CPU 2 walks the task group list in parallel to sched_offline_group(),
specifically, it'll read the soon to be unlinked task group entry at
(1). Unlinking it on CPU 1 at (2) therefore won't prevent CPU 2 from
still passing it on to tg_unthrottle_up(). CPU 1 now tries to unlink
all cfs_rq's via list_del_leaf_cfs_rq() in
unregister_fair_sched_group().  Meanwhile CPU 2 will re-add some of
these at (3), which is the cause of the UAF later on.

To prevent this additional race from happening, we need to wait until
walk_tg_tree_from() has finished traversing the task groups, i.e.
after the RCU read critical section ends in (4). Afterwards we're safe
to call unregister_fair_sched_group(), as each new walk won't see the
dying task group any more.

On top of that, we need to wait yet another RCU grace period after
unregister_fair_sched_group() to ensure print_cfs_stats(), which might
run concurrently, always sees valid objects, i.e. not already free'd
ones.

This patch survives Michal's reproducer[2] for 8h+ now, which used to
trigger within minutes before.

  [1] https://lore.kernel.org/lkml/20211011172236.11223-1-mkoutny@suse.com/
  [2] https://lore.kernel.org/lkml/20211102160228.GA57072@blackbody.suse.cz/

Fixes: a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
[peterz: shuffle code around a bit]
Reported-by: Kevin Tanguy <kevin.tanguy@corp.ovh.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2021-11-11 13:09:33 +01:00
Vincent Donnefort 42dc938a59 sched/core: Mitigate race cpus_share_cache()/update_top_cache_domain()
Nothing protects the access to the per_cpu variable sd_llc_id. When testing
the same CPU (i.e. this_cpu == that_cpu), a race condition exists with
update_top_cache_domain(). One scenario being:

              CPU1                            CPU2
  ==================================================================

  per_cpu(sd_llc_id, CPUX) => 0
                                    partition_sched_domains_locked()
      				      detach_destroy_domains()
  cpus_share_cache(CPUX, CPUX)          update_top_cache_domain(CPUX)
    per_cpu(sd_llc_id, CPUX) => 0
                                          per_cpu(sd_llc_id, CPUX) = CPUX
    per_cpu(sd_llc_id, CPUX) => CPUX
    return false

ttwu_queue_cond() wouldn't catch smp_processor_id() == cpu and the result
is a warning triggered from ttwu_queue_wakelist().

Avoid a such race in cpus_share_cache() by always returning true when
this_cpu == that_cpu.

Fixes: 518cd62341 ("sched: Only queue remote wakeups when crossing cache boundaries")
Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211104175120.857087-1-vincent.donnefort@arm.com
2021-11-11 13:09:32 +01:00
Linus Torvalds a41b74451b kernel.sys.v5.16
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Merge tag 'kernel.sys.v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull prctl updates from Christian Brauner:
 "This contains the missing prctl uapi pieces for PR_SCHED_CORE.

  In order to activate core scheduling the caller is expected to specify
  the scope of the new core scheduling domain.

  For example, passing 2 in the 4th argument of

     prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, <pid>,  2, 0);

  would indicate that the new core scheduling domain encompasses all
  tasks in the process group of <pid>. Specifying 0 would only create a
  core scheduling domain for the thread identified by <pid> and 2 would
  encompass the whole thread-group of <pid>.

  Note, the values 0, 1, and 2 correspond to PIDTYPE_PID, PIDTYPE_TGID,
  and PIDTYPE_PGID. A first version tried to expose those values
  directly to which I objected because:

   - PIDTYPE_* is an enum that is kernel internal which we should not
     expose to userspace directly.

   - PIDTYPE_* indicates what a given struct pid is used for it doesn't
     express a scope.

  But what the 4th argument of PR_SCHED_CORE prctl() expresses is the
  scope of the operation, i.e. the scope of the core scheduling domain
  at creation time. So Eugene's patch now simply introduces three new
  defines PR_SCHED_CORE_SCOPE_THREAD, PR_SCHED_CORE_SCOPE_THREAD_GROUP,
  and PR_SCHED_CORE_SCOPE_PROCESS_GROUP. They simply express what
  happens.

  This has been on the mailing list for quite a while with all relevant
  scheduler folks Cced. I announced multiple times that I'd pick this up
  if I don't see or her anyone else doing it. None of this touches
  proper scheduler code but only concerns uapi so I think this is fine.

  With core scheduling being quite common now for vm managers (e.g.
  moving individual vcpu threads into their own core scheduling domain)
  and container managers (e.g. moving the init process into its own core
  scheduling domain and letting all created children inherit it) having
  to rely on raw numbers passed as the 4th argument in prctl() is a bit
  annoying and everyone is starting to come up with their own defines"

* tag 'kernel.sys.v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  uapi/linux/prctl: provide macro definitions for the PR_SCHED_CORE type argument
2021-11-10 16:10:47 -08:00
Linus Torvalds 512b7931ad Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton:
 "257 patches.

  Subsystems affected by this patch series: scripts, ocfs2, vfs, and
  mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
  gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
  pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
  memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
  vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
  cleanups, kfence, and damon)"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
  mm/damon: remove return value from before_terminate callback
  mm/damon: fix a few spelling mistakes in comments and a pr_debug message
  mm/damon: simplify stop mechanism
  Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
  Docs/admin-guide/mm/damon/start: simplify the content
  Docs/admin-guide/mm/damon/start: fix a wrong link
  Docs/admin-guide/mm/damon/start: fix wrong example commands
  mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
  mm/damon: remove unnecessary variable initialization
  Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
  mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
  selftests/damon: support watermarks
  mm/damon/dbgfs: support watermarks
  mm/damon/schemes: activate schemes based on a watermarks mechanism
  tools/selftests/damon: update for regions prioritization of schemes
  mm/damon/dbgfs: support prioritization weights
  mm/damon/vaddr,paddr: support pageout prioritization
  mm/damon/schemes: prioritize regions within the quotas
  mm/damon/selftests: support schemes quotas
  mm/damon/dbgfs: support quotas of schemes
  ...
2021-11-06 14:08:17 -07:00
Geert Uytterhoeven 61bb6cd2f7 mm: move node_reclaim_distance to fix NUMA without SMP
Patch series "Fix NUMA without SMP".

SuperH is the only architecture which still supports NUMA without SMP,
for good reasons (various memories scattered around the address space,
each with varying latencies).

This series fixes two build errors due to variables and functions used
by the NUMA code being provided by SMP-only source files or sections.

This patch (of 2):

If CONFIG_NUMA=y, but CONFIG_SMP=n (e.g. sh/migor_defconfig):

    sh4-linux-gnu-ld: mm/page_alloc.o: in function `get_page_from_freelist':
    page_alloc.c:(.text+0x2c24): undefined reference to `node_reclaim_distance'

Fix this by moving the declaration of node_reclaim_distance from an
SMP-only to a generic file.

Link: https://lkml.kernel.org/r/cover.1631781495.git.geert+renesas@glider.be
Link: https://lkml.kernel.org/r/6432666a648dde85635341e6c918cee97c97d264.1631781495.git.geert+renesas@glider.be
Fixes: a55c7454a8 ("sched/topology: Improve load balancing on AMD EPYC systems")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Suggested-by: Matt Fleming <matt@codeblueprint.co.uk>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Cc: Rich Felker <dalias@libc.org>
Cc: Gon Solo <gonsolo@gmail.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:38 -07:00
Linus Torvalds 01463374c5 cpu-to-thread_info update for v5.16-rc1
Cross-architecture update to move task_struct::cpu back into thread_info
 on arm64, x86, s390, powerpc, and riscv. All Acked by arch maintainers.
 
 Quoting Ard Biesheuvel:
 
 "Move task_struct::cpu back into thread_info
 
  Keeping CPU in task_struct is problematic for architectures that define
  raw_smp_processor_id() in terms of this field, as it requires
  linux/sched.h to be included, which causes a lot of pain in terms of
  circular dependencies (aka 'header soup')
 
  This series moves it back into thread_info (where it came from) for all
  architectures that enable THREAD_INFO_IN_TASK, addressing the header
  soup issue as well as some pointless differences in the implementations
  of task_cpu() and set_task_cpu()."
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Merge tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull thread_info update to move 'cpu' back from task_struct from Kees Cook:
 "Cross-architecture update to move task_struct::cpu back into
  thread_info on arm64, x86, s390, powerpc, and riscv. All Acked by arch
  maintainers.

  Quoting Ard Biesheuvel:

     'Move task_struct::cpu back into thread_info

      Keeping CPU in task_struct is problematic for architectures that
      define raw_smp_processor_id() in terms of this field, as it
      requires linux/sched.h to be included, which causes a lot of pain
      in terms of circular dependencies (aka 'header soup')

      This series moves it back into thread_info (where it came from)
      for all architectures that enable THREAD_INFO_IN_TASK, addressing
      the header soup issue as well as some pointless differences in the
      implementations of task_cpu() and set_task_cpu()'"

* tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  riscv: rely on core code to keep thread_info::cpu updated
  powerpc: smp: remove hack to obtain offset of task_struct::cpu
  sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y
  powerpc: add CPU field to struct thread_info
  s390: add CPU field to struct thread_info
  x86: add CPU field to struct thread_info
  arm64: add CPU field to struct thread_info
2021-11-01 17:00:05 -07:00
Linus Torvalds 9a7e0a90a4 Scheduler updates:
- Revert the printk format based wchan() symbol resolution as it can leak
    the raw value in case that the symbol is not resolvable.
 
  - Make wchan() more robust and work with all kind of unwinders by
    enforcing that the task stays blocked while unwinding is in progress.
 
  - Prevent sched_fork() from accessing an invalid sched_task_group
 
  - Improve asymmetric packing logic
 
  - Extend scheduler statistics to RT and DL scheduling classes and add
    statistics for bandwith burst to the SCHED_FAIR class.
 
  - Properly account SCHED_IDLE entities
 
  - Prevent a potential deadlock when initial priority is assigned to a
    newly created kthread. A recent change to plug a race between cpuset and
    __sched_setscheduler() introduced a new lock dependency which is now
    triggered. Break the lock dependency chain by moving the priority
    assignment to the thread function.
 
  - Fix the idle time reporting in /proc/uptime for NOHZ enabled systems.
 
  - Improve idle balancing in general and especially for NOHZ enabled
    systems.
 
  - Provide proper interfaces for live patching so it does not have to
    fiddle with scheduler internals.
 
  - Add cluster aware scheduling support.
 
  - A small set of tweaks for RT (irqwork, wait_task_inactive(), various
    scheduler options and delaying mmdrop)
 
  - The usual small tweaks and improvements all over the place
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Merge tag 'sched-core-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Thomas Gleixner:

 - Revert the printk format based wchan() symbol resolution as it can
   leak the raw value in case that the symbol is not resolvable.

 - Make wchan() more robust and work with all kind of unwinders by
   enforcing that the task stays blocked while unwinding is in progress.

 - Prevent sched_fork() from accessing an invalid sched_task_group

 - Improve asymmetric packing logic

 - Extend scheduler statistics to RT and DL scheduling classes and add
   statistics for bandwith burst to the SCHED_FAIR class.

 - Properly account SCHED_IDLE entities

 - Prevent a potential deadlock when initial priority is assigned to a
   newly created kthread. A recent change to plug a race between cpuset
   and __sched_setscheduler() introduced a new lock dependency which is
   now triggered. Break the lock dependency chain by moving the priority
   assignment to the thread function.

 - Fix the idle time reporting in /proc/uptime for NOHZ enabled systems.

 - Improve idle balancing in general and especially for NOHZ enabled
   systems.

 - Provide proper interfaces for live patching so it does not have to
   fiddle with scheduler internals.

 - Add cluster aware scheduling support.

 - A small set of tweaks for RT (irqwork, wait_task_inactive(), various
   scheduler options and delaying mmdrop)

 - The usual small tweaks and improvements all over the place

* tag 'sched-core-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (69 commits)
  sched/fair: Cleanup newidle_balance
  sched/fair: Remove sysctl_sched_migration_cost condition
  sched/fair: Wait before decaying max_newidle_lb_cost
  sched/fair: Skip update_blocked_averages if we are defering load balance
  sched/fair: Account update_blocked_averages in newidle_balance cost
  x86: Fix __get_wchan() for !STACKTRACE
  sched,x86: Fix L2 cache mask
  sched/core: Remove rq_relock()
  sched: Improve wake_up_all_idle_cpus() take #2
  irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RT
  irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RT
  irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.
  sched/rt: Annotate the RT balancing logic irqwork as IRQ_WORK_HARD_IRQ
  sched: Add cluster scheduler level for x86
  sched: Add cluster scheduler level in core and related Kconfig for ARM64
  topology: Represent clusters of CPUs within a die
  sched: Disable -Wunused-but-set-variable
  sched: Add wrapper for get_wchan() to keep task blocked
  x86: Fix get_wchan() to support the ORC unwinder
  proc: Use task_is_running() for wchan in /proc/$pid/stat
  ...
2021-11-01 13:48:52 -07:00
Linus Torvalds 595b28fb0c Locking updates:
- Move futex code into kernel/futex/ and split up the kitchen sink into
    seperate files to make integration of sys_futex_waitv() simpler.
 
  - Add a new sys_futex_waitv() syscall which allows to wait on multiple
    futexes. The main use case is emulating Windows' WaitForMultipleObjects
    which allows Wine to improve the performance of Windows Games. Also
    native Linux games can benefit from this interface as this is a common
    wait pattern for this kind of applications.
 
  - Add context to ww_mutex_trylock() to provide a path for i915 to rework
    their eviction code step by step without making lockdep upset until the
    final steps of rework are completed. It's also useful for regulator and
    TTM to avoid dropping locks in the non contended path.
 
  - Lockdep and might_sleep() cleanups and improvements
 
  - A few improvements for the RT substitutions.
 
  - The usual small improvements and cleanups.
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Merge tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Thomas Gleixner:

 - Move futex code into kernel/futex/ and split up the kitchen sink into
   seperate files to make integration of sys_futex_waitv() simpler.

 - Add a new sys_futex_waitv() syscall which allows to wait on multiple
   futexes.

   The main use case is emulating Windows' WaitForMultipleObjects which
   allows Wine to improve the performance of Windows Games. Also native
   Linux games can benefit from this interface as this is a common wait
   pattern for this kind of applications.

 - Add context to ww_mutex_trylock() to provide a path for i915 to
   rework their eviction code step by step without making lockdep upset
   until the final steps of rework are completed. It's also useful for
   regulator and TTM to avoid dropping locks in the non contended path.

 - Lockdep and might_sleep() cleanups and improvements

 - A few improvements for the RT substitutions.

 - The usual small improvements and cleanups.

* tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
  locking: Remove spin_lock_flags() etc
  locking/rwsem: Fix comments about reader optimistic lock stealing conditions
  locking: Remove rcu_read_{,un}lock() for preempt_{dis,en}able()
  locking/rwsem: Disable preemption for spinning region
  docs: futex: Fix kernel-doc references
  futex: Fix PREEMPT_RT build
  futex2: Documentation: Document sys_futex_waitv() uAPI
  selftests: futex: Test sys_futex_waitv() wouldblock
  selftests: futex: Test sys_futex_waitv() timeout
  selftests: futex: Add sys_futex_waitv() test
  futex,arm: Wire up sys_futex_waitv()
  futex,x86: Wire up sys_futex_waitv()
  futex: Implement sys_futex_waitv()
  futex: Simplify double_lock_hb()
  futex: Split out wait/wake
  futex: Split out requeue
  futex: Rename mark_wake_futex()
  futex: Rename: match_futex()
  futex: Rename: hb_waiter_{inc,dec,pending}()
  futex: Split out PI futex
  ...
2021-11-01 13:15:36 -07:00
Linus Torvalds 33c8846c81 for-5.16/block-2021-10-29
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Merge tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:

 - mq-deadline accounting improvements (Bart)

 - blk-wbt timer fix (Andrea)

 - Untangle the block layer includes (Christoph)

 - Rework the poll support to be bio based, which will enable adding
   support for polling for bio based drivers (Christoph)

 - Block layer core support for multi-actuator drives (Damien)

 - blk-crypto improvements (Eric)

 - Batched tag allocation support (me)

 - Request completion batching support (me)

 - Plugging improvements (me)

 - Shared tag set improvements (John)

 - Concurrent queue quiesce support (Ming)

 - Cache bdev in ->private_data for block devices (Pavel)

 - bdev dio improvements (Pavel)

 - Block device invalidation and block size improvements (Xie)

 - Various cleanups, fixes, and improvements (Christoph, Jackie,
   Masahira, Tejun, Yu, Pavel, Zheng, me)

* tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block: (174 commits)
  blk-mq-debugfs: Show active requests per queue for shared tags
  block: improve readability of blk_mq_end_request_batch()
  virtio-blk: Use blk_validate_block_size() to validate block size
  loop: Use blk_validate_block_size() to validate block size
  nbd: Use blk_validate_block_size() to validate block size
  block: Add a helper to validate the block size
  block: re-flow blk_mq_rq_ctx_init()
  block: prefetch request to be initialized
  block: pass in blk_mq_tags to blk_mq_rq_ctx_init()
  block: add rq_flags to struct blk_mq_alloc_data
  block: add async version of bio_set_polled
  block: kill DIO_MULTI_BIO
  block: kill unused polling bits in __blkdev_direct_IO()
  block: avoid extra iter advance with async iocb
  block: Add independent access ranges support
  blk-mq: don't issue request directly in case that current is to be blocked
  sbitmap: silence data race warning
  blk-cgroup: synchronize blkg creation against policy deactivation
  block: refactor bio_iov_bvec_set()
  block: add single bio async direct IO helper
  ...
2021-11-01 09:19:50 -07:00
Vincent Guittot 8ea9183db4 sched/fair: Cleanup newidle_balance
update_next_balance() uses sd->last_balance which is not modified by
load_balance() so we can merge the 2 calls in one place.

No functional change

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-6-vincent.guittot@linaro.org
2021-10-31 11:11:38 +01:00
Vincent Guittot c5b0a7eefc sched/fair: Remove sysctl_sched_migration_cost condition
With a default value of 500us, sysctl_sched_migration_cost is
significanlty higher than the cost of load_balance. Remove the
condition and rely on the sd->max_newidle_lb_cost to abort
newidle_balance.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-5-vincent.guittot@linaro.org
2021-10-31 11:11:38 +01:00
Vincent Guittot e60b56e46b sched/fair: Wait before decaying max_newidle_lb_cost
Decay max_newidle_lb_cost only when it has not been updated for a while
and ensure to not decay a recently changed value.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-4-vincent.guittot@linaro.org
2021-10-31 11:11:38 +01:00
Vincent Guittot 9d783c8dd1 sched/fair: Skip update_blocked_averages if we are defering load balance
In newidle_balance(), the scheduler skips load balance to the new idle cpu
when the 1st sd of this_rq is:

   this_rq->avg_idle < sd->max_newidle_lb_cost

Doing a costly call to update_blocked_averages() will not be useful and
simply adds overhead when this condition is true.

Check the condition early in newidle_balance() to skip
update_blocked_averages() when possible.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-3-vincent.guittot@linaro.org
2021-10-31 11:11:37 +01:00
Vincent Guittot 9e9af819db sched/fair: Account update_blocked_averages in newidle_balance cost
The time spent to update the blocked load can be significant depending of
the complexity fo the cgroup hierarchy. Take this time into account in
the cost of the 1st load balance of a newly idle cpu.

Also reduce the number of call to sched_clock_cpu() and track more actual
work.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-2-vincent.guittot@linaro.org
2021-10-31 11:11:37 +01:00
Peng Wang eaed27d0d0 sched/core: Remove rq_relock()
After the removal of migrate_tasks(), there is no user of
rq_relock() left, so remove it.

Signed-off-by: Peng Wang <rocking@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/449948fdf9be4764b3929c52572917dd25eef758.1634611953.git.rocking@linux.alibaba.com
2021-10-22 15:32:46 +02:00
Christoph Hellwig 008f75a20e block: cleanup the flush plug helpers
Consolidate the various helpers into a single blk_flush_plug helper that
takes a plk_plug and the from_scheduler bool and switch all callsites to
call it directly.  Checks that the plug is non-NULL must be performed by
the caller, something that most already do anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211020144119.142582-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-10-20 09:56:11 -06:00
Woody Lin 63acd42c0d sched/scs: Reset the shadow stack when idle_task_exit
Commit f1a0a376ca ("sched/core: Initialize the idle task with
preemption disabled") removed the init_idle() call from
idle_thread_get(). This was the sole call-path on hotplug that resets
the Shadow Call Stack (scs) Stack Pointer (sp).

Not resetting the scs-sp leads to scs overflow after enough hotplug
cycles. Therefore add an explicit scs_task_reset() to the hotplug code
to make sure the scs-sp does get reset on hotplug.

Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Signed-off-by: Woody Lin <woodylin@google.com>
[peterz: Changelog]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211012083521.973587-1-woodylin@google.com
2021-10-19 17:46:11 +02:00
Christoph Hellwig 6a5850d129 sched: move the <linux/blkdev.h> include out of kernel/sched/sched.h
Only core.c needs blkdev.h, so move the #include statement there.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-10-18 06:17:01 -06:00
Sebastian Andrzej Siewior da6ff09943 sched/rt: Annotate the RT balancing logic irqwork as IRQ_WORK_HARD_IRQ
The push-IPI logic for RT tasks expects to be invoked from hardirq
context. One reason is that a RT task on the remote CPU would block the
softirq processing on PREEMPT_RT and so avoid pulling / balancing the RT
tasks as intended.

Annotate root_domain::rto_push_work as IRQ_WORK_HARD_IRQ.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-2-bigeasy@linutronix.de
2021-10-15 11:25:16 +02:00
Barry Song 778c558f49 sched: Add cluster scheduler level in core and related Kconfig for ARM64
This patch adds scheduler level for clusters and automatically enables
the load balance among clusters. It will directly benefit a lot of
workload which loves more resources such as memory bandwidth, caches.

Testing has widely been done in two different hardware configurations of
Kunpeng920:

 24 cores in one NUMA(6 clusters in each NUMA node);
 32 cores in one NUMA(8 clusters in each NUMA node)

Workload is running on either one NUMA node or four NUMA nodes, thus,
this can estimate the effect of cluster spreading w/ and w/o NUMA load
balance.

* Stream benchmark:

4threads stream (on 1NUMA * 24cores = 24cores)
                stream                 stream
                w/o patch              w/ patch
MB/sec copy     29929.64 (   0.00%)    32932.68 (  10.03%)
MB/sec scale    29861.10 (   0.00%)    32710.58 (   9.54%)
MB/sec add      27034.42 (   0.00%)    32400.68 (  19.85%)
MB/sec triad    27225.26 (   0.00%)    31965.36 (  17.41%)

6threads stream (on 1NUMA * 24cores = 24cores)
                stream                 stream
                w/o patch              w/ patch
MB/sec copy     40330.24 (   0.00%)    42377.68 (   5.08%)
MB/sec scale    40196.42 (   0.00%)    42197.90 (   4.98%)
MB/sec add      37427.00 (   0.00%)    41960.78 (  12.11%)
MB/sec triad    37841.36 (   0.00%)    42513.64 (  12.35%)

12threads stream (on 1NUMA * 24cores = 24cores)
                stream                 stream
                w/o patch              w/ patch
MB/sec copy     52639.82 (   0.00%)    53818.04 (   2.24%)
MB/sec scale    52350.30 (   0.00%)    53253.38 (   1.73%)
MB/sec add      53607.68 (   0.00%)    55198.82 (   2.97%)
MB/sec triad    54776.66 (   0.00%)    56360.40 (   2.89%)

Thus, it could help memory-bound workload especially under medium load.
Similar improvement is also seen in lkp-pbzip2:

* lkp-pbzip2 benchmark

2-96 threads (on 4NUMA * 24cores = 96cores)
                  lkp-pbzip2              lkp-pbzip2
                  w/o patch               w/ patch
Hmean     tput-2   11062841.57 (   0.00%)  11341817.51 *   2.52%*
Hmean     tput-5   26815503.70 (   0.00%)  27412872.65 *   2.23%*
Hmean     tput-8   41873782.21 (   0.00%)  43326212.92 *   3.47%*
Hmean     tput-12  61875980.48 (   0.00%)  64578337.51 *   4.37%*
Hmean     tput-21 105814963.07 (   0.00%) 111381851.01 *   5.26%*
Hmean     tput-30 150349470.98 (   0.00%) 156507070.73 *   4.10%*
Hmean     tput-48 237195937.69 (   0.00%) 242353597.17 *   2.17%*
Hmean     tput-79 360252509.37 (   0.00%) 362635169.23 *   0.66%*
Hmean     tput-96 394571737.90 (   0.00%) 400952978.48 *   1.62%*

2-24 threads (on 1NUMA * 24cores = 24cores)
                 lkp-pbzip2               lkp-pbzip2
                 w/o patch                w/ patch
Hmean     tput-2   11071705.49 (   0.00%)  11296869.10 *   2.03%*
Hmean     tput-4   20782165.19 (   0.00%)  21949232.15 *   5.62%*
Hmean     tput-6   30489565.14 (   0.00%)  33023026.96 *   8.31%*
Hmean     tput-8   40376495.80 (   0.00%)  42779286.27 *   5.95%*
Hmean     tput-12  61264033.85 (   0.00%)  62995632.78 *   2.83%*
Hmean     tput-18  86697139.39 (   0.00%)  86461545.74 (  -0.27%)
Hmean     tput-24 104854637.04 (   0.00%) 104522649.46 *  -0.32%*

In the case of 6 threads and 8 threads, we see the greatest performance
improvement.

Similar improvement can be seen on lkp-pixz though the improvement is
smaller:

* lkp-pixz benchmark

2-24 threads lkp-pixz (on 1NUMA * 24cores = 24cores)
                  lkp-pixz               lkp-pixz
                  w/o patch              w/ patch
Hmean     tput-2   6486981.16 (   0.00%)  6561515.98 *   1.15%*
Hmean     tput-4  11645766.38 (   0.00%) 11614628.43 (  -0.27%)
Hmean     tput-6  15429943.96 (   0.00%) 15957350.76 *   3.42%*
Hmean     tput-8  19974087.63 (   0.00%) 20413746.98 *   2.20%*
Hmean     tput-12 28172068.18 (   0.00%) 28751997.06 *   2.06%*
Hmean     tput-18 39413409.54 (   0.00%) 39896830.55 *   1.23%*
Hmean     tput-24 49101815.85 (   0.00%) 49418141.47 *   0.64%*

* SPECrate benchmark

4,8,16 copies mcf_r(on 1NUMA * 32cores = 32cores)
		Base     	 	Base
		Run Time   	 	Rate
		-------  	 	---------
4 Copies	w/o 580 (w/ 570)       	w/o 11.1 (w/ 11.3)
8 Copies	w/o 647 (w/ 605)       	w/o 20.0 (w/ 21.4, +7%)
16 Copies	w/o 844 (w/ 844)       	w/o 30.6 (w/ 30.6)

32 Copies(on 4NUMA * 32 cores = 128cores)
[w/o patch]
                 Base     Base        Base
Benchmarks       Copies  Run Time     Rate
--------------- -------  ---------  ---------
500.perlbench_r      32        584       87.2  *
502.gcc_r            32        503       90.2  *
505.mcf_r            32        745       69.4  *
520.omnetpp_r        32       1031       40.7  *
523.xalancbmk_r      32        597       56.6  *
525.x264_r            1         --            CE
531.deepsjeng_r      32        336      109    *
541.leela_r          32        556       95.4  *
548.exchange2_r      32        513      163    *
557.xz_r             32        530       65.2  *
 Est. SPECrate2017_int_base              80.3

[w/ patch]
                  Base     Base        Base
Benchmarks       Copies  Run Time     Rate
--------------- -------  ---------  ---------
500.perlbench_r      32        580      87.8 (+0.688%)  *
502.gcc_r            32        477      95.1 (+5.432%)  *
505.mcf_r            32        644      80.3 (+13.574%) *
520.omnetpp_r        32        942      44.6 (+9.58%)   *
523.xalancbmk_r      32        560      60.4 (+6.714%%) *
525.x264_r            1         --           CE
531.deepsjeng_r      32        337      109  (+0.000%) *
541.leela_r          32        554      95.6 (+0.210%) *
548.exchange2_r      32        515      163  (+0.000%) *
557.xz_r             32        524      66.0 (+1.227%) *
 Est. SPECrate2017_int_base              83.7 (+4.062%)

On the other hand, it is slightly helpful to CPU-bound tasks like
kernbench:

* 24-96 threads kernbench (on 4NUMA * 24cores = 96cores)
                     kernbench              kernbench
                     w/o cluster            w/ cluster
Min       user-24    12054.67 (   0.00%)    12024.19 (   0.25%)
Min       syst-24     1751.51 (   0.00%)     1731.68 (   1.13%)
Min       elsp-24      600.46 (   0.00%)      598.64 (   0.30%)
Min       user-48    12361.93 (   0.00%)    12315.32 (   0.38%)
Min       syst-48     1917.66 (   0.00%)     1892.73 (   1.30%)
Min       elsp-48      333.96 (   0.00%)      332.57 (   0.42%)
Min       user-96    12922.40 (   0.00%)    12921.17 (   0.01%)
Min       syst-96     2143.94 (   0.00%)     2110.39 (   1.56%)
Min       elsp-96      211.22 (   0.00%)      210.47 (   0.36%)
Amean     user-24    12063.99 (   0.00%)    12030.78 *   0.28%*
Amean     syst-24     1755.20 (   0.00%)     1735.53 *   1.12%*
Amean     elsp-24      601.60 (   0.00%)      600.19 (   0.23%)
Amean     user-48    12362.62 (   0.00%)    12315.56 *   0.38%*
Amean     syst-48     1921.59 (   0.00%)     1894.95 *   1.39%*
Amean     elsp-48      334.10 (   0.00%)      332.82 *   0.38%*
Amean     user-96    12925.27 (   0.00%)    12922.63 (   0.02%)
Amean     syst-96     2146.66 (   0.00%)     2122.20 *   1.14%*
Amean     elsp-96      211.96 (   0.00%)      211.79 (   0.08%)

Note this patch isn't an universal win, it might hurt those workload
which can benefit from packing. Though tasks which want to take
advantages of lower communication latency of one cluster won't
necessarily been packed in one cluster while kernel is not aware of
clusters, they have some chance to be randomly packed. But this
patch will make them more likely spread.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Tested-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2021-10-15 11:25:16 +02:00
Peter Zijlstra 37b47298ab sched: Disable -Wunused-but-set-variable
The compilers can't deal with obvious DCE vs that warning, resulting
in code like:

	if (0) {
		sched sched_statistics *stats;

		stats = __schedstats_from_se(se);

		...
	}

triggering the warning. Kill the warning to make the robots stop
reporting this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YWWPLnaZGybHsTkv@hirez.programming.kicks-ass.net
2021-10-15 11:25:15 +02:00
Kees Cook 42a20f86dc sched: Add wrapper for get_wchan() to keep task blocked
Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> [arm]
Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64]
Link: https://lkml.kernel.org/r/20211008111626.332092234@infradead.org
2021-10-15 11:25:14 +02:00
Zhang Qiao 4ef0c5c6b5 kernel/sched: Fix sched_fork() access an invalid sched_task_group
There is a small race between copy_process() and sched_fork()
where child->sched_task_group point to an already freed pointer.

	parent doing fork()      | someone moving the parent
				 | to another cgroup
  -------------------------------+-------------------------------
  copy_process()
      + dup_task_struct()<1>
				  parent move to another cgroup,
				  and free the old cgroup. <2>
      + sched_fork()
	+ __set_task_cpu()<3>
	+ task_fork_fair()
	  + sched_slice()<4>

In the worst case, this bug can lead to "use-after-free" and
cause panic as shown above:

  (1) parent copy its sched_task_group to child at <1>;

  (2) someone move the parent to another cgroup and free the old
      cgroup at <2>;

  (3) the sched_task_group and cfs_rq that belong to the old cgroup
      will be accessed at <3> and <4>, which cause a panic:

  [] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
  [] PGD 8000001fa0a86067 P4D 8000001fa0a86067 PUD 2029955067 PMD 0
  [] Oops: 0000 [#1] SMP PTI
  [] CPU: 7 PID: 648398 Comm: ebizzy Kdump: loaded Tainted: G           OE    --------- -  - 4.18.0.x86_64+ #1
  [] RIP: 0010:sched_slice+0x84/0xc0

  [] Call Trace:
  []  task_fork_fair+0x81/0x120
  []  sched_fork+0x132/0x240
  []  copy_process.part.5+0x675/0x20e0
  []  ? __handle_mm_fault+0x63f/0x690
  []  _do_fork+0xcd/0x3b0
  []  do_syscall_64+0x5d/0x1d0
  []  entry_SYSCALL_64_after_hwframe+0x65/0xca
  [] RIP: 0033:0x7f04418cd7e1

Between cgroup_can_fork() and cgroup_post_fork(), the cgroup
membership and thus sched_task_group can't change. So update child's
sched_task_group at sched_post_fork() and move task_fork() and
__set_task_cpu() (where accees the sched_task_group) from sched_fork()
to sched_post_fork().

Fixes: 8323f26ce3 ("sched: Fix race in task_group")
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lkml.kernel.org/r/20210915064030.2231-1-zhangqiao22@huawei.com
2021-10-14 13:09:58 +02:00
Yicong Yang f9ec6fea20 sched/topology: Remove unused numa_distance in cpu_attach_domain()
numa_distance in cpu_attach_domain() is introduced in
commit b5b217346d ("sched/topology: Warn when NUMA diameter > 2")
to warn user when NUMA diameter > 2 as we'll misrepresent
the scheduler topology structures at that time. This is
fixed by Barry in commit 585b6d2723 ("sched/topology: fix the issue
groups don't span domain->span for NUMA diameter > 2") and
numa_distance is unused now. So remove it.

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20210915063158.80639-1-yangyicong@hisilicon.com
2021-10-14 13:09:58 +02:00
Bharata B Rao 7d380f24fe sched/numa: Fix a few comments
Fix a few comments to help understand them better.

Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-4-bharata@amd.com
2021-10-14 13:09:58 +02:00
Bharata B Rao 5b763a14a5 sched/numa: Remove the redundant member numa_group::fault_cpus
numa_group::fault_cpus is actually a pointer to the region
in numa_group::faults[] where NUMA_CPU stats are located.

Remove this redundant member and use numa_group::faults[NUMA_CPU]
directly like it is done for similar per-process numa fault stats.

There is no functionality change due to this commit.

Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-3-bharata@amd.com
2021-10-14 13:09:58 +02:00
Bharata B Rao 7a2341fc1f sched/numa: Replace hard-coded number by a define in numa_task_group()
While allocating group fault stats, task_numa_group()
is using a hard coded number 4. Replace this by
NR_NUMA_HINT_FAULT_STATS.

No functionality change in this commit.

Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-2-bharata@amd.com
2021-10-14 13:09:58 +02:00
Peter Zijlstra 8850cb663b sched: Simplify wake_up_*idle*()
Simplify and make wake_up_if_idle() more robust, also don't iterate
the whole machine with preempt_disable() in it's caller:
wake_up_all_idle_cpus().

This prepares for another wake_up_if_idle() user that needs a full
do_idle() cycle.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.769328779@infradead.org
2021-10-07 13:51:15 +02:00
Peter Zijlstra 9b3c4ab304 sched,rcu: Rework try_invoke_on_locked_down_task()
Give try_invoke_on_locked_down_task() a saner name and have it return
an int so that the caller might distinguish between different reasons
of failure.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.649944917@infradead.org
2021-10-07 13:51:15 +02:00
Peter Zijlstra f6ac18fafc sched: Improve try_invoke_on_locked_down_task()
Clarify and tighten try_invoke_on_locked_down_task().

Basically the function calls @func under task_rq_lock(), except it
avoids taking rq->lock when possible.

This makes calling @func unconditional (the function will get renamed
in a later patch to remove the try).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.589323576@infradead.org
2021-10-07 13:51:15 +02:00
Peter Zijlstra 769fdf83df sched: Fix DEBUG && !SCHEDSTATS warn
When !SCHEDSTATS schedstat_enabled() is an unconditional 0 and the
whole block doesn't exist, however GCC figures the scoped variable
'stats' is unused and complains about it.

Upgrade the warning from -Wunused-variable to -Wunused-but-set-variable
by writing it in two statements. This fixes the build because the new
warning is in W=1.

Given that whole if(0) {} thing, I don't feel motivated to change
things overly much and quite strongly feel this is the compiler being
daft.

Fixes: cb3e971c435d ("sched: Make struct sched_statistics independent of fair sched class")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2021-10-06 10:30:57 +02:00
Vincent Guittot a7ba894821 sched/fair: Removed useless update of p->recent_used_cpu
Since commit 89aafd67f2 ("sched/fair: Use prev instead of new target as recent_used_cpu"),
p->recent_used_cpu is unconditionnaly set with prev.

Fixes: 89aafd67f2 ("sched/fair: Use prev instead of new target as recent_used_cpu")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20210928103544.27489-1-vincent.guittot@linaro.org
2021-10-05 15:52:17 +02:00
Thomas Gleixner b945efcdd0 sched: Remove pointless preemption disable in sched_submit_work()
Neither wq_worker_sleeping() nor io_wq_worker_sleeping() require to be invoked
with preemption disabled:

  - The worker flag checks operations only need to be serialized against
    the worker thread itself.

  - The accounting and worker pool operations are serialized with locks.

which means that disabling preemption has neither a reason nor a
value. Remove it and update the stale comment.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lkml.kernel.org/r/8735pnafj7.ffs@tglx
2021-10-05 15:52:15 +02:00
Thomas Gleixner 670721c7bd sched: Move kprobes cleanup out of finish_task_switch()
Doing cleanups in the tail of schedule() is a latency punishment for the
incoming task. The point of invoking kprobes_task_flush() for a dead task
is that the instances are returned and cannot leak when __schedule() is
kprobed.

Move it into the delayed cleanup.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.de
2021-10-05 15:52:14 +02:00
Thomas Gleixner 539fbb5be0 sched: Disable TTWU_QUEUE on RT
The queued remote wakeup mechanism has turned out to be suboptimal for RT
enabled kernels. The maximum latencies go up by a factor of > 5x in certain
scenarious.

This is caused by either long wake lists or by a large number of TTWU IPIs
which are processed back to back.

Disable it for RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.482262764@linutronix.de
2021-10-05 15:52:12 +02:00
Thomas Gleixner 691925f3dd sched: Limit the number of task migrations per batch on RT
Batched task migrations are a source for large latencies as they keep the
scheduler from running while processing the migrations.

Limit the batch size to 8 instead of 32 when running on a RT enabled
kernel.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.425097596@linutronix.de
2021-10-05 15:52:11 +02:00
Thomas Gleixner 8d491de6ed sched: Move mmdrop to RCU on RT
mmdrop() is invoked from finish_task_switch() by the incoming task to drop
the mm which was handed over by the previous task. mmdrop() can be quite
expensive which prevents an incoming real-time task from getting useful
work done.

Provide mmdrop_sched() which maps to mmdrop() on !RT kernels. On RT kernels
it delagates the eventually required invocation of __mmdrop() to RCU.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.648582026@linutronix.de
2021-10-05 15:52:09 +02:00
Shaokun Zhang d07b2eee45 sched: Make cookie functions static
Make cookie functions static as these are no longer invoked directly
by other code.

No functional change intended.

Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210922085735.52812-1-zhangshaokun@hisilicon.com
2021-10-05 15:52:07 +02:00
Ricardo Neri 4006a72bdd sched/fair: Consider SMT in ASYM_PACKING load balance
When deciding to pull tasks in ASYM_PACKING, it is necessary not only to
check for the idle state of the destination CPU, dst_cpu, but also of
its SMT siblings.

If dst_cpu is idle but its SMT siblings are busy, performance suffers
if it pulls tasks from a medium priority CPU that does not have SMT
siblings.

Implement asym_smt_can_pull_tasks() to inspect the state of the SMT
siblings of both dst_cpu and the CPUs in the candidate busiest group.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-7-ricardo.neri-calderon@linux.intel.com
2021-10-05 15:52:06 +02:00
Ricardo Neri aafc917a3c sched/fair: Carve out logic to mark a group for asymmetric packing
Create a separate function, sched_asym(). A subsequent changeset will
introduce logic to deal with SMT in conjunction with asmymmetric
packing. Such logic will need the statistics of the scheduling
group provided as argument. Update them before calling sched_asym().

Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-6-ricardo.neri-calderon@linux.intel.com
2021-10-05 15:52:04 +02:00
Ricardo Neri c0d14b57fe sched/fair: Provide update_sg_lb_stats() with sched domain statistics
Before deciding to pull tasks when using asymmetric packing of tasks,
on some architectures (e.g., x86) it is necessary to know not only the
state of dst_cpu but also of its SMT siblings. The decision to classify
a candidate busiest group as group_asym_packing is done in
update_sg_lb_stats(). Give this function access to the scheduling domain
statistics, which contains the statistics of the local group.

Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-5-ricardo.neri-calderon@linux.intel.com
2021-10-05 15:52:03 +02:00
Ricardo Neri 6025643596 sched/fair: Optimize checking for group_asym_packing
sched_asmy_prefer() always returns false when called on the local group. By
checking local_group, we can avoid additional checks and invoking
sched_asmy_prefer() when it is not needed. No functional changes are
introduced.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-4-ricardo.neri-calderon@linux.intel.com
2021-10-05 15:52:02 +02:00
Ricardo Neri 16d364ba6e sched/topology: Introduce sched_group::flags
There exist situations in which the load balance needs to know the
properties of the CPUs in a scheduling group. When using asymmetric
packing, for instance, the load balancer needs to know not only the
state of dst_cpu but also of its SMT siblings, if any.

Use the flags of the child scheduling domains to initialize scheduling
group flags. This will reflect the properties of the CPUs in the
group.

A subsequent changeset will make use of these new flags. No functional
changes are introduced.

Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-3-ricardo.neri-calderon@linux.intel.com
2021-10-05 15:52:00 +02:00
Frederic Weisbecker c597bfddc9 sched: Provide Kconfig support for default dynamic preempt mode
Currently the boot defined preempt behaviour (aka dynamic preempt)
selects full preemption by default when the "preempt=" boot parameter
is omitted. However distros may rather want to default to either
no preemption or voluntary preemption.

To provide with this flexibility, make dynamic preemption a visible
Kconfig option and adapt the preemption behaviour selected by the user
to either static or dynamic preemption.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210914103134.11309-1-frederic@kernel.org
2021-10-05 15:51:56 +02:00
YueHaibing 32ed980c30 sched: Remove unused inline function __rq_clock_broken()
These is no caller in tree since commit
523e979d31 ("sched/core: Use PELT for scale_rt_capacity()")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210914095244.52780-1-yuehaibing@huawei.com
2021-10-05 15:51:55 +02:00
Yafang Shao b5eb4a5f65 sched/dl: Support schedstats for deadline sched class
After we make the struct sched_statistics and the helpers of it
independent of fair sched class, we can easily use the schedstats
facility for deadline sched class.

The schedstat usage in DL sched class is similar with fair sched class,
for example,
                    fair                        deadline
    enqueue         update_stats_enqueue_fair   update_stats_enqueue_dl
    dequeue         update_stats_dequeue_fair   update_stats_dequeue_dl
    put_prev_task   update_stats_wait_start     update_stats_wait_start_dl
    set_next_task   update_stats_wait_end       update_stats_wait_end_dl

The user can get the schedstats information in the same way in fair sched
class. For example,
           fair                            deadline
           /proc/[pid]/sched               /proc/[pid]/sched

The output of a deadline task's schedstats as follows,

$ cat /proc/69662/sched
...
se.sum_exec_runtime                          :          3067.696449
se.nr_migrations                             :                    0
sum_sleep_runtime                            :        720144.029661
sum_block_runtime                            :             0.547853
wait_start                                   :             0.000000
sleep_start                                  :      14131540.828955
block_start                                  :             0.000000
sleep_max                                    :          2999.974045
block_max                                    :             0.283637
exec_max                                     :             1.000269
slice_max                                    :             0.000000
wait_max                                     :             0.002217
wait_sum                                     :             0.762179
wait_count                                   :                  733
iowait_sum                                   :             0.547853
iowait_count                                 :                    3
nr_migrations_cold                           :                    0
nr_failed_migrations_affine                  :                    0
nr_failed_migrations_running                 :                    0
nr_failed_migrations_hot                     :                    0
nr_forced_migrations                         :                    0
nr_wakeups                                   :                  246
nr_wakeups_sync                              :                    2
nr_wakeups_migrate                           :                    0
nr_wakeups_local                             :                  244
nr_wakeups_remote                            :                    2
nr_wakeups_affine                            :                    0
nr_wakeups_affine_attempts                   :                    0
nr_wakeups_passive                           :                    0
nr_wakeups_idle                              :                    0
...

The sched:sched_stat_{wait, sleep, iowait, blocked} tracepoints can
be used to trace deadlline tasks as well.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210905143547.4668-9-laoar.shao@gmail.com
2021-10-05 15:51:53 +02:00
Yafang Shao 95fd58e8da sched/dl: Support sched_stat_runtime tracepoint for deadline sched class
The runtime of a DL task has already been there, so we only need to
add a tracepoint.

One difference between fair task and DL task is that there is no vruntime
in dl task. To reuse the sched_stat_runtime tracepoint, '0' is passed as
vruntime for DL task.

The output of this tracepoint for DL task as follows,
             top-36462   [047] d.h.  6083.452103: sched_stat_runtime: comm=top pid=36462 runtime=409898 [ns] vruntime=0 [ns]

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210905143547.4668-8-laoar.shao@gmail.com
2021-10-05 15:51:52 +02:00
Yafang Shao 57a5c2dafc sched/rt: Support schedstats for RT sched class
We want to measure the latency of RT tasks in our production
environment with schedstats facility, but currently schedstats is only
supported for fair sched class. This patch enable it for RT sched class
as well.

After we make the struct sched_statistics and the helpers of it
independent of fair sched class, we can easily use the schedstats
facility for RT sched class.

The schedstat usage in RT sched class is similar with fair sched class,
for example,
                fair                        RT
enqueue         update_stats_enqueue_fair   update_stats_enqueue_rt
dequeue         update_stats_dequeue_fair   update_stats_dequeue_rt
put_prev_task   update_stats_wait_start     update_stats_wait_start_rt
set_next_task   update_stats_wait_end       update_stats_wait_end_rt

The user can get the schedstats information in the same way in fair sched
class. For example,
       fair                            RT
       /proc/[pid]/sched               /proc/[pid]/sched

schedstats is not supported for RT group.

The output of a RT task's schedstats as follows,
$ cat /proc/10349/sched
...
sum_sleep_runtime                            :           972.434535
sum_block_runtime                            :           960.433522
wait_start                                   :        188510.871584
sleep_start                                  :             0.000000
block_start                                  :             0.000000
sleep_max                                    :            12.001013
block_max                                    :           952.660622
exec_max                                     :             0.049629
slice_max                                    :             0.000000
wait_max                                     :             0.018538
wait_sum                                     :             0.424340
wait_count                                   :                   49
iowait_sum                                   :           956.495640
iowait_count                                 :                   24
nr_migrations_cold                           :                    0
nr_failed_migrations_affine                  :                    0
nr_failed_migrations_running                 :                    0
nr_failed_migrations_hot                     :                    0
nr_forced_migrations                         :                    0
nr_wakeups                                   :                   49
nr_wakeups_sync                              :                    0
nr_wakeups_migrate                           :                    0
nr_wakeups_local                             :                   49
nr_wakeups_remote                            :                    0
nr_wakeups_affine                            :                    0
nr_wakeups_affine_attempts                   :                    0
nr_wakeups_passive                           :                    0
nr_wakeups_idle                              :                    0
...

The sched:sched_stat_{wait, sleep, iowait, blocked} tracepoints can
be used to trace RT tasks as well. The output of these tracepoints for a
RT tasks as follows,

- runtime
          stress-10352   [004] d.h.  1035.382286: sched_stat_runtime: comm=stress pid=10352 runtime=995769 [ns] vruntime=0 [ns]
          [vruntime=0 means it is a RT task]

- wait
          <idle>-0       [004] dN..  1227.688544: sched_stat_wait: comm=stress pid=10352 delay=46849882 [ns]

- blocked
     kworker/4:1-465     [004] dN..  1585.676371: sched_stat_blocked: comm=stress pid=17194 delay=189963 [ns]

- iowait
     kworker/4:1-465     [004] dN..  1585.675330: sched_stat_iowait: comm=stress pid=17189 delay=182848 [ns]

- sleep
           sleep-18194   [023] dN..  1780.891840: sched_stat_sleep: comm=sleep.sh pid=17767 delay=1001160770 [ns]
           sleep-18196   [023] dN..  1781.893208: sched_stat_sleep: comm=sleep.sh pid=17767 delay=1001161970 [ns]
           sleep-18197   [023] dN..  1782.894544: sched_stat_sleep: comm=sleep.sh pid=17767 delay=1001128840 [ns]
           [ In sleep.sh, it sleeps 1 sec each time. ]

[lkp@intel.com: reported build failure in earlier version]

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210905143547.4668-7-laoar.shao@gmail.com
2021-10-05 15:51:51 +02:00
Yafang Shao ed7b564cfd sched/rt: Support sched_stat_runtime tracepoint for RT sched class
The runtime of a RT task has already been there, so we only need to
add a tracepoint.

One difference between fair task and RT task is that there is no vruntime
in RT task. To reuse the sched_stat_runtime tracepoint, '0' is passed as
vruntime for RT task.

The output of this tracepoint for RT task as follows,
          stress-9748    [039] d.h.   113.519352: sched_stat_runtime: comm=stress pid=9748 runtime=997573 [ns] vruntime=0 [ns]
          stress-9748    [039] d.h.   113.520352: sched_stat_runtime: comm=stress pid=9748 runtime=997627 [ns] vruntime=0 [ns]
          stress-9748    [039] d.h.   113.521352: sched_stat_runtime: comm=stress pid=9748 runtime=998203 [ns] vruntime=0 [ns]

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210905143547.4668-6-laoar.shao@gmail.com
2021-10-05 15:51:49 +02:00
Yafang Shao 847fc0cd06 sched: Introduce task block time in schedstats
Currently in schedstats we have sum_sleep_runtime and iowait_sum, but
there's no metric to show how long the task is in D state.  Once a task in
D state, it means the task is blocked in the kernel, for example the
task may be waiting for a mutex. The D state is more frequent than
iowait, and it is more critital than S state. So it is worth to add a
metric to measure it.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210905143547.4668-5-laoar.shao@gmail.com
2021-10-05 15:51:48 +02:00
Yafang Shao 60f2415e19 sched: Make schedstats helpers independent of fair sched class
The original prototype of the schedstats helpers are

  update_stats_wait_*(struct cfs_rq *cfs_rq, struct sched_entity *se)

The cfs_rq in these helpers is used to get the rq_clock, and the se is
used to get the struct sched_statistics and the struct task_struct. In
order to make these helpers available by all sched classes, we can pass
the rq, sched_statistics and task_struct directly.

Then the new helpers are

  update_stats_wait_*(struct rq *rq, struct task_struct *p,
                      struct sched_statistics *stats)

which are independent of fair sched class.

To avoid vmlinux growing too large or introducing ovehead when
!schedstat_enabled(), some new helpers after schedstat_enabled() are also
introduced, Suggested by Mel. These helpers are in sched/stats.c,

  __update_stats_wait_*(struct rq *rq, struct task_struct *p,
                        struct sched_statistics *stats)

The size of vmlinux as follows,
                      Before          After
  Size of vmlinux     826308552       826304640
The size is a litte smaller as some functions are not inlined again after
the change.

I also compared the sched performance with 'perf bench sched pipe',
suggested by Mel. The result as followsi (in usecs/op),
                             Before                After
  kernel.sched_schedstats=0  5.2~5.4               5.2~5.4
  kernel.sched_schedstats=1  5.3~5.5               5.3~5.5

[These data is a little difference with the prev version, that is
because my old test machine is destroyed so I have to use a new
different test machine.]
Almost no difference.

No functional change.

[lkp@intel.com: reported build failure in prev version]

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20210905143547.4668-4-laoar.shao@gmail.com
2021-10-05 15:51:47 +02:00
Yafang Shao ceeadb83ae sched: Make struct sched_statistics independent of fair sched class
If we want to use the schedstats facility to trace other sched classes, we
should make it independent of fair sched class. The struct sched_statistics
is the schedular statistics of a task_struct or a task_group. So we can
move it into struct task_struct and struct task_group to achieve the goal.

After the patch, schestats are orgnized as follows,

    struct task_struct {
       ...
       struct sched_entity se;
       struct sched_rt_entity rt;
       struct sched_dl_entity dl;
       ...
       struct sched_statistics stats;
       ...
   };

Regarding the task group, schedstats is only supported for fair group
sched, and a new struct sched_entity_stats is introduced, suggested by
Peter -

    struct sched_entity_stats {
        struct sched_entity     se;
        struct sched_statistics stats;
    } __no_randomize_layout;

Then with the se in a task_group, we can easily get the stats.

The sched_statistics members may be frequently modified when schedstats is
enabled, in order to avoid impacting on random data which may in the same
cacheline with them, the struct sched_statistics is defined as cacheline
aligned.

As this patch changes the core struct of scheduler, so I verified the
performance it may impact on the scheduler with 'perf bench sched
pipe', suggested by Mel. Below is the result, in which all the values
are in usecs/op.
                                  Before               After
      kernel.sched_schedstats=0  5.2~5.4               5.2~5.4
      kernel.sched_schedstats=1  5.3~5.5               5.3~5.5
[These data is a little difference with the earlier version, that is
 because my old test machine is destroyed so I have to use a new
 different test machine.]

Almost no impact on the sched performance.

No functional change.

[lkp@intel.com: reported build failure in earlier version]

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20210905143547.4668-3-laoar.shao@gmail.com
2021-10-05 15:51:45 +02:00
Yafang Shao a2dcb276ff sched/fair: Use __schedstat_set() in set_next_entity()
schedstat_enabled() has been already checked, so we can use
__schedstat_set() directly.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20210905143547.4668-2-laoar.shao@gmail.com
2021-10-05 15:51:44 +02:00
Huaixin Chang bcb1704a1e sched/fair: Add cfs bandwidth burst statistics
Two new statistics are introduced to show the internal of burst feature
and explain why burst helps or not.

nr_bursts:  number of periods bandwidth burst occurs
burst_time: cumulative wall-time (in nanoseconds) that any cpus has
	    used above quota in respective periods

Co-developed-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Signed-off-by: Shanpei Chen <shanpeic@linux.alibaba.com>
Co-developed-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Huaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210830032215.16302-2-changhuaixin@linux.alibaba.com
2021-10-05 15:51:40 +02:00
Josh Don 2cae3948ed sched: adjust sleeper credit for SCHED_IDLE entities
Give reduced sleeper credit to SCHED_IDLE entities. As a result, woken
SCHED_IDLE entities will take longer to preempt normal entities.

The benefit of this change is to make it less likely that a newly woken
SCHED_IDLE entity will preempt a short-running normal entity before it
blocks.

We still give a small sleeper credit to SCHED_IDLE entities, so that
idle<->idle competition retains some fairness.

Example: With HZ=1000, spawned four threads affined to one cpu, one of
which was set to SCHED_IDLE. Without this patch, wakeup latency for the
SCHED_IDLE thread was ~1-2ms, with the patch the wakeup latency was
~5ms.

Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Jiang Biao <benbjiang@tencent.com>
Link: https://lore.kernel.org/r/20210820010403.946838-5-joshdon@google.com
2021-10-05 15:51:39 +02:00
Josh Don 51ce83ed52 sched: reduce sched slice for SCHED_IDLE entities
Use a small, non-scaled min granularity for SCHED_IDLE entities, when
competing with normal entities. This reduces the latency of getting
a normal entity back on cpu, at the expense of increased context
switch frequency of SCHED_IDLE entities.

The benefit of this change is to reduce the round-robin latency for
normal entities when competing with a SCHED_IDLE entity.

Example: on a machine with HZ=1000, spawned two threads, one of which is
SCHED_IDLE, and affined to one cpu. Without this patch, the SCHED_IDLE
thread runs for 4ms then waits for 1.4s. With this patch, it runs for
1ms and waits 340ms (as it round-robins with the other thread).

Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210820010403.946838-4-joshdon@google.com
2021-10-05 15:51:37 +02:00
Josh Don a480addecc sched: Account number of SCHED_IDLE entities on each cfs_rq
Adds cfs_rq->idle_nr_running, which accounts the number of idle entities
directly enqueued on the cfs_rq.

Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210820010403.946838-3-joshdon@google.com
2021-10-05 15:51:36 +02:00
Peter Zijlstra bc9ffef31b sched/core: Simplify core-wide task selection
Tao suggested a two-pass task selection to avoid the retry loop.

Not only does it avoid the retry loop, it results in *much* simpler
code.

This also fixes an issue spotted by Josh Don where, for SMT3+, we can
forget to update max on the first pass and get to do an extra round.

Suggested-by: Tao Zhou <tao.zhou@linux.dev>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Don <joshdon@google.com>
Reviewed-by: Vineeth Pillai (Microsoft) <vineethrp@gmail.com>
Link: https://lkml.kernel.org/r/YSS9+k1teA9oPEKl@hirez.programming.kicks-ass.net
2021-10-05 15:51:33 +02:00
Sebastian Andrzej Siewior c33627e9a1 sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD
With PREEMPT_RT enabled all hrtimers callbacks will be invoked in
softirq mode unless they are explicitly marked as HRTIMER_MODE_HARD.
During boot kthread_bind() is used for the creation of per-CPU threads
and then hangs in wait_task_inactive() if the ksoftirqd is not
yet up and running.
The hang disappeared since commit
   26c7295be0 ("kthread: Do not preempt current task if it is going to call schedule()")

but enabling function trace on boot reliably leads to the freeze on boot
behaviour again.
The timer in wait_task_inactive() can not be directly used by a user
interface to abuse it and create a mass wake up of several tasks at the
same time leading to long sections with disabled interrupts.
Therefore it is safe to make the timer HRTIMER_MODE_REL_HARD.

Switch the timer to HRTIMER_MODE_REL_HARD.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210826170408.vm7rlj7odslshwch@linutronix.de
2021-10-05 15:51:32 +02:00
Valentin Schneider 7fd7a9e0ca sched/fair: Trigger nohz.next_balance updates when a CPU goes NOHZ-idle
Consider a system with some NOHZ-idle CPUs, such that

  nohz.idle_cpus_mask = S
  nohz.next_balance = T

When a new CPU k goes NOHZ idle (nohz_balance_enter_idle()), we end up
with:

  nohz.idle_cpus_mask = S \U {k}
  nohz.next_balance = T

Note that the nohz.next_balance hasn't changed - it won't be updated until
a NOHZ balance is triggered. This is problematic if the newly NOHZ idle CPU
has an earlier rq.next_balance than the other NOHZ idle CPUs, IOW if:

  cpu_rq(k).next_balance < nohz.next_balance

In such scenarios, the existing nohz.next_balance will prevent any NOHZ
balance from happening, which itself will prevent nohz.next_balance from
being updated to this new cpu_rq(k).next_balance. Unnecessary load balance
delays of over 12ms caused by this were observed on an arm64 RB5 board.

Use the new nohz.needs_update flag to mark the presence of newly-idle CPUs
that need their rq->next_balance to be collated into
nohz.next_balance. Trigger a NOHZ_NEXT_KICK when the flag is set.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210823111700.2842997-3-valentin.schneider@arm.com
2021-10-05 15:51:31 +02:00
Valentin Schneider efd984c481 sched/fair: Add NOHZ balancer flag for nohz.next_balance updates
A following patch will trigger NOHZ idle balances as a means to update
nohz.next_balance. Vincent noted that blocked load updates can have
non-negligible overhead, which should be avoided if the intent is to only
update nohz.next_balance.

Add a new NOHZ balance kick flag, NOHZ_NEXT_KICK. Gate NOHZ blocked load
update by the presence of NOHZ_STATS_KICK - currently all NOHZ balance
kicks will have the NOHZ_STATS_KICK flag set, so no change in behaviour is
expected.

Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210823111700.2842997-2-valentin.schneider@arm.com
2021-10-05 15:51:30 +02:00
Mel Gorman 703066188f sched/fair: Null terminate buffer when updating tunable_scaling
This patch null-terminates the temporary buffer in sched_scaling_write()
so kstrtouint() does not return failure and checks the value is valid.

Before:
  $ cat /sys/kernel/debug/sched/tunable_scaling
  1
  $ echo 0 > /sys/kernel/debug/sched/tunable_scaling
  -bash: echo: write error: Invalid argument
  $ cat /sys/kernel/debug/sched/tunable_scaling
  1

After:
  $ cat /sys/kernel/debug/sched/tunable_scaling
  1
  $ echo 0 > /sys/kernel/debug/sched/tunable_scaling
  $ cat /sys/kernel/debug/sched/tunable_scaling
  0
  $ echo 3 > /sys/kernel/debug/sched/tunable_scaling
  -bash: echo: write error: Invalid argument

Fixes: 8a99b6833c ("sched: Move SCHED_DEBUG sysctl to debugfs")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210927114635.GH3959@techsingularity.net
2021-10-01 13:57:57 +02:00
Michal Koutný 2630cde267 sched/fair: Add ancestors of unthrottled undecayed cfs_rq
Since commit a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to
list on unthrottle") we add cfs_rqs with no runnable tasks but not fully
decayed into the load (leaf) list. We may ignore adding some ancestors
and therefore breaking tmp_alone_branch invariant. This broke LTP test
cfs_bandwidth01 and it was partially fixed in commit fdaba61ef8
("sched/fair: Ensure that the CFS parent is added after unthrottling").

I noticed the named test still fails even with the fix (but with low
probability, 1 in ~1000 executions of the test). The reason is when
bailing out of unthrottle_cfs_rq early, we may miss adding ancestors of
the unthrottled cfs_rq, thus, not joining tmp_alone_branch properly.

Fix this by adding ancestors if we notice the unthrottled cfs_rq was
added to the load list.

Fixes: a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Odin Ugedal <odin@uged.al>
Link: https://lore.kernel.org/r/20210917153037.11176-1-mkoutny@suse.com
2021-10-01 13:57:57 +02:00
Thomas Gleixner 50e081b96e sched: Make RCU nest depth distinct in __might_resched()
For !RT kernels RCU nest depth in __might_resched() is always expected to
be 0, but on RT kernels it can be non zero while the preempt count is
expected to be always 0.

Instead of playing magic games in interpreting the 'preempt_offset'
argument, rename it to 'offsets' and use the lower 8 bits for the expected
preempt count, allow to hand in the expected RCU nest depth in the upper
bits and adopt the __might_resched() code and related checks and printks.

The affected call sites are updated in subsequent steps.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.243232823@linutronix.de
2021-10-01 13:57:51 +02:00
Thomas Gleixner 8d713b699e sched: Make might_sleep() output less confusing
might_sleep() output is pretty informative, but can be confusing at times
especially with PREEMPT_RCU when the check triggers due to a voluntary
sleep inside a RCU read side critical section:

 BUG: sleeping function called from invalid context at kernel/test.c:110
 in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
 Preemption disabled at: migrate_disable+0x33/0xa0

in_atomic() is 0, but it still tells that preemption was disabled at
migrate_disable(), which is completely useless because preemption is not
disabled. But the interesting information to decode the above, i.e. the RCU
nesting depth, is not printed.

That becomes even more confusing when might_sleep() is invoked from
cond_resched_lock() within a RCU read side critical section. Here the
expected preemption count is 1 and not 0.

 BUG: sleeping function called from invalid context at kernel/test.c:131
 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
 Preemption disabled at: test_cond_lock+0xf3/0x1c0

So in_atomic() is set, which is expected as the caller holds a spinlock,
but it's unclear why this is broken and the preempt disable IP is just
pointing at the correct place, i.e. spin_lock(), which is obviously not
helpful either.

Make that more useful in general:

 - Print preempt_count() and the expected value

and for the CONFIG_PREEMPT_RCU case:

 - Print the RCU read side critical section nesting depth

 - Print the preempt disable IP only when preempt count
   does not have the expected value.

So the might_sleep() dump from a within a preemptible RCU read side
critical section becomes:

 BUG: sleeping function called from invalid context at kernel/test.c:110
 in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
 preempt_count: 0, expected: 0
 RCU nest depth: 1, expected: 0

and the cond_resched_lock() case becomes:

 BUG: sleeping function called from invalid context at kernel/test.c:141
 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
 preempt_count: 1, expected: 1
 RCU nest depth: 1, expected: 0

which makes is pretty obvious what's going on. For all other cases the
preempt disable IP is still printed as before:

 BUG: sleeping function called from invalid context at kernel/test.c: 156
 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0
 preempt_count: 1, expected: 0
 RCU nest depth: 0, expected: 0
 Preemption disabled at:
 [<ffffffff82b48326>] test_might_sleep+0xbe/0xf8

 BUG: sleeping function called from invalid context at kernel/test.c: 163
 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0
 preempt_count: 1, expected: 0
 RCU nest depth: 1, expected: 0
 Preemption disabled at:
 [<ffffffff82b48326>] test_might_sleep+0x1e4/0x280

This also prepares to provide a better debugging output for RT enabled
kernels and their spinlock substitutions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.181022656@linutronix.de
2021-10-01 13:57:50 +02:00
Thomas Gleixner a45ed302b6 sched: Cleanup might_sleep() printks
Convert them to pr_*(). No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.117496067@linutronix.de
2021-10-01 13:57:50 +02:00
Thomas Gleixner 42a387566c sched: Remove preempt_offset argument from __might_sleep()
All callers hand in 0 and never will hand in anything else.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.054321586@linutronix.de
2021-10-01 13:57:50 +02:00
Thomas Gleixner 874f670e60 sched: Clean up the might_sleep() underscore zoo
__might_sleep() vs. ___might_sleep() is hard to distinguish. Aside of that
the three underscore variant is exposed to provide a checkpoint for
rescheduling points which are distinct from blocking points.

They are semantically a preemption point which means that scheduling is
state preserving. A real blocking operation, e.g. mutex_lock(), wait*(),
which cannot preserve a task state which is not equal to RUNNING.

While technically blocking on a "sleeping" spinlock in RT enabled kernels
falls into the voluntary scheduling category because it has to wait until
the contended spin/rw lock becomes available, the RT lock substitution code
can semantically be mapped to a voluntary preemption because the RT lock
substitution code and the scheduler are providing mechanisms to preserve
the task state and to take regular non-lock related wakeups into account.

Rename ___might_sleep() to __might_resched() to make the distinction of
these functions clear.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165357.928693482@linutronix.de
2021-10-01 13:57:49 +02:00
Ard Biesheuvel bcf9033e54 sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y
THREAD_INFO_IN_TASK moved the CPU field out of thread_info, but this
causes some issues on architectures that define raw_smp_processor_id()
in terms of this field, due to the fact that #include'ing linux/sched.h
to get at struct task_struct is problematic in terms of circular
dependencies.

Given that thread_info and task_struct are the same data structure
anyway when THREAD_INFO_IN_TASK=y, let's move it back so that having
access to the type definition of struct thread_info is sufficient to
reference the CPU number of the current task.

Note that this requires THREAD_INFO_IN_TASK's definition of the
task_thread_info() helper to be updated, as task_cpu() takes a
pointer-to-const, whereas task_thread_info() (which is used to generate
lvalues as well), needs a non-const pointer. So make it a macro instead.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
2021-09-30 16:13:10 +02:00
Eugene Syromiatnikov 61bc346ce6
uapi/linux/prctl: provide macro definitions for the PR_SCHED_CORE type argument
Commit 7ac592aa35 ("sched: prctl() core-scheduling interface")
made use of enum pid_type in prctl's arg4; this type and the associated
enumeration definitions are not exposed to userspace.  Christian
has suggested to provide additional macro definitions that convey
the meaning of the type argument more in alignment with its actual
usage, and this patch does exactly that.

Link: https://lore.kernel.org/r/20210825170613.GA3884@asgard.redhat.com
Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Complements: 7ac592aa35 ("sched: prctl() core-scheduling interface")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-09-29 13:00:05 +02:00
Linus Torvalds 56c244382f - Make sure the idle timer expires in hardirq context, on PREEMPT_RT
- Make sure the run-queue balance callback is invoked only on the outgoing CPU
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Merge tag 'sched_urgent_for_v5.15_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Borislav Petkov:

 - Make sure the idle timer expires in hardirq context, on PREEMPT_RT

 - Make sure the run-queue balance callback is invoked only on the
   outgoing CPU

* tag 'sched_urgent_for_v5.15_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Prevent balance_push() on remote runqueues
  sched/idle: Make the idle timer expire in hard interrupt context
2021-09-12 11:37:41 -07:00
Thomas Gleixner 868ad33bfa sched: Prevent balance_push() on remote runqueues
sched_setscheduler() and rt_mutex_setprio() invoke the run-queue balance
callback after changing priorities or the scheduling class of a task. The
run-queue for which the callback is invoked can be local or remote.

That's not a problem for the regular rq::push_work which is serialized with
a busy flag in the run-queue struct, but for the balance_push() work which
is only valid to be invoked on the outgoing CPU that's wrong. It not only
triggers the debug warning, but also leaves the per CPU variable push_work
unprotected, which can result in double enqueues on the stop machine list.

Remove the warning and validate that the function is invoked on the
outgoing CPU.

Fixes: ae79270232 ("sched: Optimize finish_lock_switch()")
Reported-by: Sebastian Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87zgt1hdw7.ffs@tglx
2021-09-09 11:27:23 +02:00
Sebastian Andrzej Siewior 9848417926 sched/idle: Make the idle timer expire in hard interrupt context
The intel powerclamp driver will setup a per-CPU worker with RT
priority. The worker will then invoke play_idle() in which it remains in
the idle poll loop until it is stopped by the timer it started earlier.

That timer needs to expire in hard interrupt context on PREEMPT_RT.
Otherwise the timer will expire in ksoftirqd as a SOFT timer but that task
won't be scheduled on the CPU because its priority is lower than the
priority of the worker which is in the idle loop.

Always expire the idle timer in hard interrupt context.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210906113034.jgfxrjdvxnjqgtmc@linutronix.de
2021-09-09 10:36:16 +02:00
Linus Torvalds 5cbba60596 Power management updates for 5.15-rc1
- Address 3 PCI device power management issues (Rafael Wysocki).
 
  - Add Power Limit4 support for Alder Lake to the Intel RAPL power
    capping driver (Sumeet Pawnikar).
 
  - Add HWP guaranteed performance change notification support to
    the intel_pstate driver (Srinivas Pandruvada).
 
  - Replace deprecated CPU-hotplug functions in code related to power
    management (Sebastian Andrzej Siewior).
 
  - Update CPU PM notifiers to use raw spinlocks (Valentin Schneider).
 
  - Add support for 'required-opps' DT property to the generic power
    domains (genpd) framework and use this property for I2C on ARM64
    sc7180 (Rajendra Nayak).
 
  - Fix Kconfig issue related to genpd (Geert Uytterhoeven).
 
  - Increase energy calculation precision in the Energy Model (Lukasz
    Luba).
 
  - Fix kobject deletion in the exit code of the schedutil cpufreq
    governor (Kevin Hao).
 
  - Unmark some functions as kernel-doc in the PM core to avoid
    false-positive documentation build warnings (Randy Dunlap).
 
  - Check RTC features instead of ops in suspend_test Alexandre
    Belloni).
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Merge tag 'pm-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management updates from Rafael Wysocki:
 "These address some PCI device power management issues, add new
  hardware support to the RAPL power capping driver, add HWP guaranteed
  performance change notification support to the intel_pstate driver,
  replace deprecated CPU-hotplug functions in a few places, update CPU
  PM notifiers to use raw spinlocks, update the PM domains framework
  (new DT property support, Kconfig fix), do a couple of cleanups in
  code related to system sleep, and improve the energy model and the
  schedutil cpufreq governor.

  Specifics:

   - Address 3 PCI device power management issues (Rafael Wysocki).

   - Add Power Limit4 support for Alder Lake to the Intel RAPL power
     capping driver (Sumeet Pawnikar).

   - Add HWP guaranteed performance change notification support to the
     intel_pstate driver (Srinivas Pandruvada).

   - Replace deprecated CPU-hotplug functions in code related to power
     management (Sebastian Andrzej Siewior).

   - Update CPU PM notifiers to use raw spinlocks (Valentin Schneider).

   - Add support for 'required-opps' DT property to the generic power
     domains (genpd) framework and use this property for I2C on ARM64
     sc7180 (Rajendra Nayak).

   - Fix Kconfig issue related to genpd (Geert Uytterhoeven).

   - Increase energy calculation precision in the Energy Model (Lukasz
     Luba).

   - Fix kobject deletion in the exit code of the schedutil cpufreq
     governor (Kevin Hao).

   - Unmark some functions as kernel-doc in the PM core to avoid
     false-positive documentation build warnings (Randy Dunlap).

   - Check RTC features instead of ops in suspend_test Alexandre
     Belloni)"

* tag 'pm-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM: domains: Fix domain attach for CONFIG_PM_OPP=n
  powercap: Add Power Limit4 support for Alder Lake SoC
  cpufreq: intel_pstate: Process HWP Guaranteed change notification
  thermal: intel: Allow processing of HWP interrupt
  notifier: Remove atomic_notifier_call_chain_robust()
  PM: cpu: Make notifier chain use a raw_spinlock_t
  PM: sleep: unmark 'state' functions as kernel-doc
  arm64: dts: sc7180: Add required-opps for i2c
  PM: domains: Add support for 'required-opps' to set default perf state
  opp: Don't print an error if required-opps is missing
  cpufreq: schedutil: Use kobject release() method to free sugov_tunables
  PM: EM: Increase energy calculation precision
  PM: sleep: check RTC features instead of ops in suspend_test
  PM: sleep: s2idle: Replace deprecated CPU-hotplug functions
  cpufreq: Replace deprecated CPU-hotplug functions
  powercap: intel_rapl: Replace deprecated CPU-hotplug functions
  PCI: PM: Enable PME if it can be signaled from D3cold
  PCI: PM: Avoid forcing PCI_D0 for wakeup reasons inconsistently
  PCI: Use pci_update_current_state() in pci_enable_device_flags()
2021-08-31 13:21:58 -07:00
Linus Torvalds e5e726f7bb Updates for locking and atomics:
The regular pile:
 
   - A few improvements to the mutex code
 
   - Documentation updates for atomics to clarify the difference between
     cmpxchg() and try_cmpxchg() and to explain the forward progress
     expectations.
 
   - Simplification of the atomics fallback generator
 
   - The addition of arch_atomic_long*() variants and generic arch_*()
     bitops based on them.
 
   - Add the missing might_sleep() invocations to the down*() operations of
     semaphores.
 
 The PREEMPT_RT locking core:
 
   - Scheduler updates to support the state preserving mechanism for
     'sleeping' spin- and rwlocks on RT. This mechanism is carefully
     preserving the state of the task when blocking on a 'sleeping' spin- or
     rwlock and takes regular wake-ups targeted at the same task into
     account. The preserved or updated (via a regular wakeup) state is
     restored when the lock has been acquired.
 
   - Restructuring of the rtmutex code so it can be utilized and extended
     for the RT specific lock variants.
 
   - Restructuring of the ww_mutex code to allow sharing of the ww_mutex
     specific functionality for rtmutex based ww_mutexes.
 
   - Header file disentangling to allow substitution of the regular lock
     implementations with the PREEMPT_RT variants without creating an
     unmaintainable #ifdef mess.
 
   - Shared base code for the PREEMPT_RT specific rw_semaphore and rwlock
     implementations. Contrary to the regular rw_semaphores and rwlocks the
     PREEMPT_RT implementation is writer unfair because it is infeasible to
     do priority inheritance on multiple readers. Experience over the years
     has shown that real-time workloads are not the typical workloads which
     are sensitive to writer starvation. The alternative solution would be
     to allow only a single reader which has been tried and discarded as it
     is a major bottleneck especially for mmap_sem. Aside of that many of
     the writer starvation critical usage sites have been converted to a
     writer side mutex/spinlock and RCU read side protections in the past
     decade so that the issue is less prominent than it used to be.
 
   - The actual rtmutex based lock substitutions for PREEMPT_RT enabled
     kernels which affect mutex, ww_mutex, rw_semaphore, spinlock_t and
     rwlock_t. The spin/rw_lock*() functions disable migration across the
     critical section to preserve the existing semantics vs. per CPU
     variables.
 
   - Rework of the futex REQUEUE_PI mechanism to handle the case of early
     wake-ups which interleave with a re-queue operation to prevent the
     situation that a task would be blocked on both the rtmutex associated
     to the outer futex and the rtmutex based hash bucket spinlock.
 
     While this situation cannot happen on !RT enabled kernels the changes
     make the underlying concurrency problems easier to understand in
     general. As a result the difference between !RT and RT kernels is
     reduced to the handling of waiting for the critical section. !RT
     kernels simply spin-wait as before and RT kernels utilize rcu_wait().
 
   - The substitution of local_lock for PREEMPT_RT with a spinlock which
     protects the critical section while staying preemptible. The CPU
     locality is established by disabling migration.
 
   The underlying concepts of this code have been in use in PREEMPT_RT for
   way more than a decade. The code has been refactored several times over
   the years and this final incarnation has been optimized once again to be
   as non-intrusive as possible, i.e. the RT specific parts are mostly
   isolated.
 
   It has been extensively tested in the 5.14-rt patch series and it has
   been verified that !RT kernels are not affected by these changes.
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Merge tag 'locking-core-2021-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking and atomics updates from Thomas Gleixner:
 "The regular pile:

   - A few improvements to the mutex code

   - Documentation updates for atomics to clarify the difference between
     cmpxchg() and try_cmpxchg() and to explain the forward progress
     expectations.

   - Simplification of the atomics fallback generator

   - The addition of arch_atomic_long*() variants and generic arch_*()
     bitops based on them.

   - Add the missing might_sleep() invocations to the down*() operations
     of semaphores.

  The PREEMPT_RT locking core:

   - Scheduler updates to support the state preserving mechanism for
     'sleeping' spin- and rwlocks on RT.

     This mechanism is carefully preserving the state of the task when
     blocking on a 'sleeping' spin- or rwlock and takes regular wake-ups
     targeted at the same task into account. The preserved or updated
     (via a regular wakeup) state is restored when the lock has been
     acquired.

   - Restructuring of the rtmutex code so it can be utilized and
     extended for the RT specific lock variants.

   - Restructuring of the ww_mutex code to allow sharing of the ww_mutex
     specific functionality for rtmutex based ww_mutexes.

   - Header file disentangling to allow substitution of the regular lock
     implementations with the PREEMPT_RT variants without creating an
     unmaintainable #ifdef mess.

   - Shared base code for the PREEMPT_RT specific rw_semaphore and
     rwlock implementations.

     Contrary to the regular rw_semaphores and rwlocks the PREEMPT_RT
     implementation is writer unfair because it is infeasible to do
     priority inheritance on multiple readers. Experience over the years
     has shown that real-time workloads are not the typical workloads
     which are sensitive to writer starvation.

     The alternative solution would be to allow only a single reader
     which has been tried and discarded as it is a major bottleneck
     especially for mmap_sem. Aside of that many of the writer
     starvation critical usage sites have been converted to a writer
     side mutex/spinlock and RCU read side protections in the past
     decade so that the issue is less prominent than it used to be.

   - The actual rtmutex based lock substitutions for PREEMPT_RT enabled
     kernels which affect mutex, ww_mutex, rw_semaphore, spinlock_t and
     rwlock_t. The spin/rw_lock*() functions disable migration across
     the critical section to preserve the existing semantics vs per-CPU
     variables.

   - Rework of the futex REQUEUE_PI mechanism to handle the case of
     early wake-ups which interleave with a re-queue operation to
     prevent the situation that a task would be blocked on both the
     rtmutex associated to the outer futex and the rtmutex based hash
     bucket spinlock.

     While this situation cannot happen on !RT enabled kernels the
     changes make the underlying concurrency problems easier to
     understand in general. As a result the difference between !RT and
     RT kernels is reduced to the handling of waiting for the critical
     section. !RT kernels simply spin-wait as before and RT kernels
     utilize rcu_wait().

   - The substitution of local_lock for PREEMPT_RT with a spinlock which
     protects the critical section while staying preemptible. The CPU
     locality is established by disabling migration.

  The underlying concepts of this code have been in use in PREEMPT_RT for
  way more than a decade. The code has been refactored several times over
  the years and this final incarnation has been optimized once again to be
  as non-intrusive as possible, i.e. the RT specific parts are mostly
  isolated.

  It has been extensively tested in the 5.14-rt patch series and it has
  been verified that !RT kernels are not affected by these changes"

* tag 'locking-core-2021-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (92 commits)
  locking/rtmutex: Return success on deadlock for ww_mutex waiters
  locking/rtmutex: Prevent spurious EDEADLK return caused by ww_mutexes
  locking/rtmutex: Dequeue waiter on ww_mutex deadlock
  locking/rtmutex: Dont dereference waiter lockless
  locking/semaphore: Add might_sleep() to down_*() family
  locking/ww_mutex: Initialize waiter.ww_ctx properly
  static_call: Update API documentation
  locking/local_lock: Add PREEMPT_RT support
  locking/spinlock/rt: Prepare for RT local_lock
  locking/rtmutex: Add adaptive spinwait mechanism
  locking/rtmutex: Implement equal priority lock stealing
  preempt: Adjust PREEMPT_LOCK_OFFSET for RT
  locking/rtmutex: Prevent lockdep false positive with PI futexes
  futex: Prevent requeue_pi() lock nesting issue on RT
  futex: Simplify handle_early_requeue_pi_wakeup()
  futex: Reorder sanity checks in futex_requeue()
  futex: Clarify comment in futex_requeue()
  futex: Restructure futex_requeue()
  futex: Correct the number of requeued waiters for PI
  futex: Remove bogus condition for requeue PI
  ...
2021-08-30 14:26:36 -07:00
Linus Torvalds 5d3c0db459 Scheduler changes for v5.15 are:
- The biggest change in this cycle is scheduler support for asymmetric
   scheduling affinity, to support the execution of legacy 32-bit tasks on
   AArch32 systems that also have 64-bit-only CPUs.
 
   Architectures can fill in this functionality by defining their
   own task_cpu_possible_mask(p). When this is done, the scheduler will
   make sure the task will only be scheduled on CPUs that support it.
 
   (The actual arm64 specific changes are not part of this tree.)
 
   For other architectures there will be no change in functionality.
 
 - Add cgroup SCHED_IDLE support
 
 - Increase node-distance flexibility & delay determining it until a CPU
   is brought online. (This enables platforms where node distance isn't
   final until the CPU is only.)
 
 - Deadline scheduler enhancements & fixes
 
 - Misc fixes & cleanups.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2021-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - The biggest change in this cycle is scheduler support for asymmetric
   scheduling affinity, to support the execution of legacy 32-bit tasks
   on AArch32 systems that also have 64-bit-only CPUs.

   Architectures can fill in this functionality by defining their own
   task_cpu_possible_mask(p). When this is done, the scheduler will make
   sure the task will only be scheduled on CPUs that support it.

   (The actual arm64 specific changes are not part of this tree.)

   For other architectures there will be no change in functionality.

 - Add cgroup SCHED_IDLE support

 - Increase node-distance flexibility & delay determining it until a CPU
   is brought online. (This enables platforms where node distance isn't
   final until the CPU is only.)

 - Deadline scheduler enhancements & fixes

 - Misc fixes & cleanups.

* tag 'sched-core-2021-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  eventfd: Make signal recursion protection a task bit
  sched/fair: Mark tg_is_idle() an inline in the !CONFIG_FAIR_GROUP_SCHED case
  sched: Introduce dl_task_check_affinity() to check proposed affinity
  sched: Allow task CPU affinity to be restricted on asymmetric systems
  sched: Split the guts of sched_setaffinity() into a helper function
  sched: Introduce task_struct::user_cpus_ptr to track requested affinity
  sched: Reject CPU affinity changes based on task_cpu_possible_mask()
  cpuset: Cleanup cpuset_cpus_allowed_fallback() use in select_fallback_rq()
  cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus()
  cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1
  sched: Introduce task_cpu_possible_mask() to limit fallback rq selection
  sched: Cgroup SCHED_IDLE support
  sched/topology: Skip updating masks for non-online nodes
  sched: Replace deprecated CPU-hotplug functions.
  sched: Skip priority checks with SCHED_FLAG_KEEP_PARAMS
  sched: Fix UCLAMP_FLAG_IDLE setting
  sched/deadline: Fix missing clock update in migrate_task_rq_dl()
  sched/fair: Avoid a second scan of target in select_idle_cpu
  sched/fair: Use prev instead of new target as recent_used_cpu
  sched: Don't report SCHED_FLAG_SUGOV in sched_getattr()
  ...
2021-08-30 13:42:10 -07:00
Linus Torvalds 4ca4256453 Merge branch 'core-rcu.2021.08.28a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU updates from Paul McKenney:
 "RCU changes for this cycle were:

   - Documentation updates

   - Miscellaneous fixes

   - Offloaded-callbacks updates

   - Updates to the nolibc library

   - Tasks-RCU updates

   - In-kernel torture-test updates

   - Torture-test scripting, perhaps most notably the pinning of
     torture-test guest OSes so as to force differences in memory
     latency. For example, in a two-socket system, a four-CPU guest OS
     will have one pair of its CPUs pinned to threads in a single core
     on one socket and the other pair pinned to threads in a single core
     on the other socket. This approach proved able to force race
     conditions that earlier testing missed. Some of these race
     conditions are still being tracked down"

* 'core-rcu.2021.08.28a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (61 commits)
  torture: Replace deprecated CPU-hotplug functions.
  rcu: Replace deprecated CPU-hotplug functions
  rcu: Print human-readable message for schedule() in RCU reader
  rcu: Explain why rcu_all_qs() is a stub in preemptible TREE RCU
  rcu: Use per_cpu_ptr to get the pointer of per_cpu variable
  rcu: Remove useless "ret" update in rcu_gp_fqs_loop()
  rcu: Mark accesses in tree_stall.h
  rcu: Make rcu_gp_init() and rcu_gp_fqs_loop noinline to conserve stack
  rcu: Mark lockless ->qsmask read in rcu_check_boost_fail()
  srcutiny: Mark read-side data races
  rcu: Start timing stall repetitions after warning complete
  rcu: Do not disable GP stall detection in rcu_cpu_stall_reset()
  rcu/tree: Handle VM stoppage in stall detection
  rculist: Unify documentation about missing list_empty_rcu()
  rcu: Mark accesses to ->rcu_read_lock_nesting
  rcu: Weaken ->dynticks accesses and updates
  rcu: Remove special bit at the bottom of the ->dynticks counter
  rcu: Fix stall-warning deadlock due to non-release of rcu_node ->lock
  rcu: Fix to include first blocked task in stall warning
  torture: Make kvm-test-1-run-qemu.sh check for reboot loops
  ...
2021-08-30 12:48:01 -07:00
Sebastian Andrzej Siewior e681dcbaa4 sched: Fix get_push_task() vs migrate_disable()
push_rt_task() attempts to move the currently running task away if the
next runnable task has migration disabled and therefore is pinned on the
current CPU.

The current task is retrieved via get_push_task() which only checks for
nr_cpus_allowed == 1, but does not check whether the task has migration
disabled and therefore cannot be moved either. The consequence is a
pointless invocation of the migration thread which correctly observes
that the task cannot be moved.

Return NULL if the task has migration disabled and cannot be moved to
another CPU.

Fixes: a7c81556ec ("sched: Fix migrate_disable() vs rt/dl balancing")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210826133738.yiotqbtdaxzjsnfj@linutronix.de
2021-08-26 19:02:00 +02:00
Ingo Molnar 366e7ad6ba sched/fair: Mark tg_is_idle() an inline in the !CONFIG_FAIR_GROUP_SCHED case
It's not actually used in the !CONFIG_FAIR_GROUP_SCHED case:

  kernel/sched/fair.c:488:12: warning: ‘tg_is_idle’ defined but not used [-Wunused-function]

Keep around a placeholder nevertheless, for API completeness. Mark it inline,
so the compiler doesn't think it must be used.

Fixes: 304000390f88: ("sched: Cgroup SCHED_IDLE support")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Josh Don <joshdon@google.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
2021-08-26 10:49:24 +02:00
Rafael J. Wysocki 43dde64bb1 Merge back cpufreq changes for v5.15. 2021-08-23 13:48:40 +02:00
Will Deacon 234b8ab647 sched: Introduce dl_task_check_affinity() to check proposed affinity
In preparation for restricting the affinity of a task during execve()
on arm64, introduce a new dl_task_check_affinity() helper function to
give an indication as to whether the restricted mask is admissible for
a deadline task.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lore.kernel.org/r/20210730112443.23245-10-will@kernel.org
2021-08-20 12:33:00 +02:00
Will Deacon 07ec77a1d4 sched: Allow task CPU affinity to be restricted on asymmetric systems
Asymmetric systems may not offer the same level of userspace ISA support
across all CPUs, meaning that some applications cannot be executed by
some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do
not feature support for 32-bit applications on both clusters.

Although userspace can carefully manage the affinity masks for such
tasks, one place where it is particularly problematic is execve()
because the CPU on which the execve() is occurring may be incompatible
with the new application image. In such a situation, it is desirable to
restrict the affinity mask of the task and ensure that the new image is
entered on a compatible CPU. From userspace's point of view, this looks
the same as if the incompatible CPUs have been hotplugged off in the
task's affinity mask. Similarly, if a subsequent execve() reverts to
a compatible image, then the old affinity is restored if it is still
valid.

In preparation for restricting the affinity mask for compat tasks on
arm64 systems without uniform support for 32-bit applications, introduce
{force,relax}_compatible_cpus_allowed_ptr(), which respectively restrict
and restore the affinity mask for a task based on the compatible CPUs.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20210730112443.23245-9-will@kernel.org
2021-08-20 12:33:00 +02:00
Will Deacon db3b02ae89 sched: Split the guts of sched_setaffinity() into a helper function
In preparation for replaying user affinity requests using a saved mask,
split sched_setaffinity() up so that the initial task lookup and
security checks are only performed when the request is coming directly
from userspace.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-8-will@kernel.org
2021-08-20 12:33:00 +02:00
Will Deacon b90ca8badb sched: Introduce task_struct::user_cpus_ptr to track requested affinity
In preparation for saving and restoring the user-requested CPU affinity
mask of a task, add a new cpumask_t pointer to 'struct task_struct'.

If the pointer is non-NULL, then the mask is copied across fork() and
freed on task exit.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-7-will@kernel.org
2021-08-20 12:33:00 +02:00
Will Deacon 234a503e67 sched: Reject CPU affinity changes based on task_cpu_possible_mask()
Reject explicit requests to change the affinity mask of a task via
set_cpus_allowed_ptr() if the requested mask is not a subset of the
mask returned by task_cpu_possible_mask(). This ensures that the
'cpus_mask' for a given task cannot contain CPUs which are incapable of
executing it, except in cases where the affinity is forced.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Reviewed-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20210730112443.23245-6-will@kernel.org
2021-08-20 12:32:59 +02:00
Will Deacon 97c0054dbe cpuset: Cleanup cpuset_cpus_allowed_fallback() use in select_fallback_rq()
select_fallback_rq() only needs to recheck for an allowed CPU if the
affinity mask of the task has changed since the last check.

Return a 'bool' from cpuset_cpus_allowed_fallback() to indicate whether
the affinity mask was updated, and use this to elide the allowed check
when the mask has been left alone.

No functional change.

Suggested-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-5-will@kernel.org
2021-08-20 12:32:59 +02:00
Will Deacon 9ae606bc74 sched: Introduce task_cpu_possible_mask() to limit fallback rq selection
Asymmetric systems may not offer the same level of userspace ISA support
across all CPUs, meaning that some applications cannot be executed by
some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do
not feature support for 32-bit applications on both clusters.

On such a system, we must take care not to migrate a task to an
unsupported CPU when forcefully moving tasks in select_fallback_rq()
in response to a CPU hot-unplug operation.

Introduce a task_cpu_possible_mask() hook which, given a task argument,
allows an architecture to return a cpumask of CPUs that are capable of
executing that task. The default implementation returns the
cpu_possible_mask, since sane machines do not suffer from per-cpu ISA
limitations that affect scheduling. The new mask is used when selecting
the fallback runqueue as a last resort before forcing a migration to the
first active CPU.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Reviewed-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20210730112443.23245-2-will@kernel.org
2021-08-20 12:32:58 +02:00
Josh Don 304000390f sched: Cgroup SCHED_IDLE support
This extends SCHED_IDLE to cgroups.

Interface: cgroup/cpu.idle.
 0: default behavior
 1: SCHED_IDLE

Extending SCHED_IDLE to cgroups means that we incorporate the existing
aspects of SCHED_IDLE; a SCHED_IDLE cgroup will count all of its
descendant threads towards the idle_h_nr_running count of all of its
ancestor cgroups. Thus, sched_idle_rq() will work properly.
Additionally, SCHED_IDLE cgroups are configured with minimum weight.

There are two key differences between the per-task and per-cgroup
SCHED_IDLE interface:

  - The cgroup interface allows tasks within a SCHED_IDLE hierarchy to
    maintain their relative weights. The entity that is "idle" is the
    cgroup, not the tasks themselves.

  - Since the idle entity is the cgroup, our SCHED_IDLE wakeup preemption
    decision is not made by comparing the current task with the woken
    task, but rather by comparing their matching sched_entity.

A typical use-case for this is a user that creates an idle and a
non-idle subtree. The non-idle subtree will dominate competition vs
the idle subtree, but the idle subtree will still be high priority vs
other users on the system. The latter is accomplished via comparing
matching sched_entity in the waken preemption path (this could also be
improved by making the sched_idle_rq() decision dependent on the
perspective of a specific task).

For now, we maintain the existing SCHED_IDLE semantics. Future patches
may make improvements that extend how we treat SCHED_IDLE entities.

The per-task_group idle field is an integer that currently only holds
either a 0 or a 1. This is explicitly typed as an integer to allow for
further extensions to this API. For example, a negative value may
indicate a highly latency-sensitive cgroup that should be preferred
for preemption/placement/etc.

Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210730020019.1487127-2-joshdon@google.com
2021-08-20 12:32:58 +02:00
Valentin Schneider 0083242c93 sched/topology: Skip updating masks for non-online nodes
The scheduler currently expects NUMA node distances to be stable from
init onwards, and as a consequence builds the related data structures
once-and-for-all at init (see sched_init_numa()).

Unfortunately, on some architectures node distance is unreliable for
offline nodes and may very well change upon onlining.

Skip over offline nodes during sched_init_numa(). Track nodes that have
been onlined at least once, and trigger a build of a node's NUMA masks
when it is first onlined post-init.

Reported-by: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210818074333.48645-1-srikar@linux.vnet.ibm.com
2021-08-20 12:32:57 +02:00
Peter Zijlstra 3c474b3239 sched: Fix Core-wide rq->lock for uninitialized CPUs
Eugene tripped over the case where rq_lock(), as called in a
for_each_possible_cpu() loop came apart because rq->core hadn't been
setup yet.

This is a somewhat unusual, but valid case.

Rework things such that rq->core is initialized to point at itself. IOW
initialize each CPU as a single threaded Core. CPU online will then join
the new CPU (thread) to an existing Core where needed.

For completeness sake, have CPU offline fully undo the state so as to
not presume the topology will match the next time it comes online.

Fixes: 9edeaea1bc ("sched: Core-wide rq->lock")
Reported-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Don <joshdon@google.com>
Tested-by: Eugene Syromiatnikov <esyr@redhat.com>
Link: https://lkml.kernel.org/r/YR473ZGeKqMs6kw+@hirez.programming.kicks-ass.net
2021-08-20 12:32:53 +02:00
Thomas Gleixner 6991436c2b sched/core: Provide a scheduling point for RT locks
RT enabled kernels substitute spin/rwlocks with 'sleeping' variants based
on rtmutexes. Blocking on such a lock is similar to preemption versus:

 - I/O scheduling and worker handling, because these functions might block
   on another substituted lock, or come from a lock contention within these
   functions.

 - RCU considers this like a preemption, because the task might be in a read
   side critical section.

Add a separate scheduling point for this, and hand a new scheduling mode
argument to __schedule() which allows, along with separate mode masks, to
handle this gracefully from within the scheduler, without proliferating that
to other subsystems like RCU.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.372319055@linutronix.de
2021-08-17 16:57:17 +02:00
Thomas Gleixner b4bfa3fcfe sched/core: Rework the __schedule() preempt argument
PREEMPT_RT needs to hand a special state into __schedule() when a task
blocks on a 'sleeping' spin/rwlock. This is required to handle
rcu_note_context_switch() correctly without having special casing in the
RCU code. From an RCU point of view the blocking on the sleeping spinlock
is equivalent to preemption, because the task might be in a read side
critical section.

schedule_debug() also has a check which would trigger with the !preempt
case, but that could be handled differently.

To avoid adding another argument and extra checks which cannot be optimized
out by the compiler, the following solution has been chosen:

 - Replace the boolean 'preempt' argument with an unsigned integer
   'sched_mode' argument and define constants to hand in:
   (0 == no preemption, 1 = preemption).

 - Add two masks to apply on that mode: one for the debug/rcu invocations,
   and one for the actual scheduling decision.

   For a non RT kernel these masks are UINT_MAX, i.e. all bits are set,
   which allows the compiler to optimize the AND operation out, because it is
   not masking out anything. IOW, it's not different from the boolean.

   RT enabled kernels will define these masks separately.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.315473019@linutronix.de
2021-08-17 16:53:43 +02:00
Thomas Gleixner 5f220be214 sched/wakeup: Prepare for RT sleeping spin/rwlocks
Waiting for spinlocks and rwlocks on non RT enabled kernels is task::state
preserving. Any wakeup which matches the state is valid.

RT enabled kernels substitutes them with 'sleeping' spinlocks. This creates
an issue vs. task::__state.

In order to block on the lock, the task has to overwrite task::__state and a
consecutive wakeup issued by the unlocker sets the state back to
TASK_RUNNING. As a consequence the task loses the state which was set
before the lock acquire and also any regular wakeup targeted at the task
while it is blocked on the lock.

To handle this gracefully, add a 'saved_state' member to task_struct which
is used in the following way:

 1) When a task blocks on a 'sleeping' spinlock, the current state is saved
    in task::saved_state before it is set to TASK_RTLOCK_WAIT.

 2) When the task unblocks and after acquiring the lock, it restores the saved
    state.

 3) When a regular wakeup happens for a task while it is blocked then the
    state change of that wakeup is redirected to operate on task::saved_state.

    This is also required when the task state is running because the task
    might have been woken up from the lock wait and has not yet restored
    the saved state.

To make it complete, provide the necessary helpers to save and restore the
saved state along with the necessary documentation how the RT lock blocking
is supposed to work.

For non-RT kernels there is no functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.258751046@linutronix.de
2021-08-17 16:49:02 +02:00
Thomas Gleixner 43295d73ad sched/wakeup: Split out the wakeup ->__state check
RT kernels have a slightly more complicated handling of wakeups due to
'sleeping' spin/rwlocks. If a task is blocked on such a lock then the
original state of the task is preserved over the blocking period, and
any regular (non lock related) wakeup has to be targeted at the
saved state to ensure that these wakeups are not lost.

Once the task acquires the lock it restores the task state from the saved state.

To avoid cluttering try_to_wake_up() with that logic, split the wakeup
state check out into an inline helper and use it at both places where
task::__state is checked against the state argument of try_to_wake_up().

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.088945085@linutronix.de
2021-08-17 16:40:54 +02:00
Sebastian Andrzej Siewior 746f5ea9c4 sched: Replace deprecated CPU-hotplug functions.
The functions get_online_cpus() and put_online_cpus() have been
deprecated during the CPU hotplug rework. They map directly to
cpus_read_lock() and cpus_read_unlock().

Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210803141621.780504-33-bigeasy@linutronix.de
2021-08-10 14:53:00 +02:00
Frederic Weisbecker 508958259b rcu: Explain why rcu_all_qs() is a stub in preemptible TREE RCU
The cond_resched() function reports an RCU quiescent state only in
non-preemptible TREE RCU implementation.  This commit therefore adds a
comment explaining why cond_resched() does nothing in preemptible kernels.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-08-06 13:41:49 -07:00
Kevin Hao e5c6b312ce cpufreq: schedutil: Use kobject release() method to free sugov_tunables
The struct sugov_tunables is protected by the kobject, so we can't free
it directly. Otherwise we would get a call trace like this:
  ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x30
  WARNING: CPU: 3 PID: 720 at lib/debugobjects.c:505 debug_print_object+0xb8/0x100
  Modules linked in:
  CPU: 3 PID: 720 Comm: a.sh Tainted: G        W         5.14.0-rc1-next-20210715-yocto-standard+ #507
  Hardware name: Marvell OcteonTX CN96XX board (DT)
  pstate: 40400009 (nZcv daif +PAN -UAO -TCO BTYPE=--)
  pc : debug_print_object+0xb8/0x100
  lr : debug_print_object+0xb8/0x100
  sp : ffff80001ecaf910
  x29: ffff80001ecaf910 x28: ffff00011b10b8d0 x27: ffff800011043d80
  x26: ffff00011a8f0000 x25: ffff800013cb3ff0 x24: 0000000000000000
  x23: ffff80001142aa68 x22: ffff800011043d80 x21: ffff00010de46f20
  x20: ffff800013c0c520 x19: ffff800011d8f5b0 x18: 0000000000000010
  x17: 6e6968207473696c x16: 5f72656d6974203a x15: 6570797420746365
  x14: 6a626f2029302065 x13: 303378302f307830 x12: 2b6e665f72656d69
  x11: ffff8000124b1560 x10: ffff800012331520 x9 : ffff8000100ca6b0
  x8 : 000000000017ffe8 x7 : c0000000fffeffff x6 : 0000000000000001
  x5 : ffff800011d8c000 x4 : ffff800011d8c740 x3 : 0000000000000000
  x2 : ffff0001108301c0 x1 : ab3c90eedf9c0f00 x0 : 0000000000000000
  Call trace:
   debug_print_object+0xb8/0x100
   __debug_check_no_obj_freed+0x1c0/0x230
   debug_check_no_obj_freed+0x20/0x88
   slab_free_freelist_hook+0x154/0x1c8
   kfree+0x114/0x5d0
   sugov_exit+0xbc/0xc0
   cpufreq_exit_governor+0x44/0x90
   cpufreq_set_policy+0x268/0x4a8
   store_scaling_governor+0xe0/0x128
   store+0xc0/0xf0
   sysfs_kf_write+0x54/0x80
   kernfs_fop_write_iter+0x128/0x1c0
   new_sync_write+0xf0/0x190
   vfs_write+0x2d4/0x478
   ksys_write+0x74/0x100
   __arm64_sys_write+0x24/0x30
   invoke_syscall.constprop.0+0x54/0xe0
   do_el0_svc+0x64/0x158
   el0_svc+0x2c/0xb0
   el0t_64_sync_handler+0xb0/0xb8
   el0t_64_sync+0x198/0x19c
  irq event stamp: 5518
  hardirqs last  enabled at (5517): [<ffff8000100cbd7c>] console_unlock+0x554/0x6c8
  hardirqs last disabled at (5518): [<ffff800010fc0638>] el1_dbg+0x28/0xa0
  softirqs last  enabled at (5504): [<ffff8000100106e0>] __do_softirq+0x4d0/0x6c0
  softirqs last disabled at (5483): [<ffff800010049548>] irq_exit+0x1b0/0x1b8

So split the original sugov_tunables_free() into two functions,
sugov_clear_global_tunables() is just used to clear the global_tunables
and the new sugov_tunables_free() is used as kobj_type::release to
release the sugov_tunables safely.

Fixes: 9bdcb44e39 ("cpufreq: schedutil: New governor based on scheduler utilization data")
Cc: 4.7+ <stable@vger.kernel.org> # 4.7+
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2021-08-06 15:34:55 +02:00
Quentin Perret f4dddf90d5 sched: Skip priority checks with SCHED_FLAG_KEEP_PARAMS
SCHED_FLAG_KEEP_PARAMS can be passed to sched_setattr to specify that
the call must not touch scheduling parameters (nice or priority). This
is particularly handy for uclamp when used in conjunction with
SCHED_FLAG_KEEP_POLICY as that allows to issue a syscall that only
impacts uclamp values.

However, sched_setattr always checks whether the priorities and nice
values passed in sched_attr are valid first, even if those never get
used down the line. This is useless at best since userspace can
trivially bypass this check to set the uclamp values by specifying low
priorities. However, it is cumbersome to do so as there is no single
expression of this that skips both RT and CFS checks at once. As such,
userspace needs to query the task policy first with e.g. sched_getattr
and then set sched_attr.sched_priority accordingly. This is racy and
slower than a single call.

As the priority and nice checks are useless when SCHED_FLAG_KEEP_PARAMS
is specified, simply inherit them in this case to match the policy
inheritance of SCHED_FLAG_KEEP_POLICY.

Reported-by: Wei Wang <wvw@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Link: https://lore.kernel.org/r/20210805102154.590709-3-qperret@google.com
2021-08-06 14:25:25 +02:00
Quentin Perret ca4984a7dd sched: Fix UCLAMP_FLAG_IDLE setting
The UCLAMP_FLAG_IDLE flag is set on a runqueue when dequeueing the last
uclamp active task (that is, when buckets.tasks reaches 0 for all
buckets) to maintain the last uclamp.max and prevent blocked util from
suddenly becoming visible.

However, there is an asymmetry in how the flag is set and cleared which
can lead to having the flag set whilst there are active tasks on the rq.
Specifically, the flag is cleared in the uclamp_rq_inc() path, which is
called at enqueue time, but set in uclamp_rq_dec_id() which is called
both when dequeueing a task _and_ in the update_uclamp_active() path. As
a result, when both uclamp_rq_{dec,ind}_id() are called from
update_uclamp_active(), the flag ends up being set but not cleared,
hence leaving the runqueue in a broken state.

Fix this by clearing the flag in update_uclamp_active() as well.

Fixes: e496187da7 ("sched/uclamp: Enforce last task's UCLAMP_MAX")
Reported-by: Rick Yiu <rickyiu@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20210805102154.590709-2-qperret@google.com
2021-08-06 14:25:25 +02:00
Dietmar Eggemann b4da13aa28 sched/deadline: Fix missing clock update in migrate_task_rq_dl()
A missing clock update is causing the following warning:

rq->clock_update_flags < RQCF_ACT_SKIP
WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453
sub_running_bw.isra.0+0x190/0x1a0
...
CPU: 112 PID: 2041 Comm: sugov:112 Tainted: G W 5.14.0-rc1 #1
Hardware name: WIWYNN Mt.Jade Server System
B81.030Z1.0007/Mt.Jade Motherboard, BIOS 1.6.20210526 (SCP:
1.06.20210526) 2021/05/26
...
Call trace:
  sub_running_bw.isra.0+0x190/0x1a0
  migrate_task_rq_dl+0xf8/0x1e0
  set_task_cpu+0xa8/0x1f0
  try_to_wake_up+0x150/0x3d4
  wake_up_q+0x64/0xc0
  __up_write+0xd0/0x1c0
  up_write+0x4c/0x2b0
  cppc_set_perf+0x120/0x2d0
  cppc_cpufreq_set_target+0xe0/0x1a4 [cppc_cpufreq]
  __cpufreq_driver_target+0x74/0x140
  sugov_work+0x64/0x80
  kthread_worker_fn+0xe0/0x230
  kthread+0x138/0x140
  ret_from_fork+0x10/0x18

The task causing this is the `cppc_fie` DL task introduced by
commit 1eb5dde674 ("cpufreq: CPPC: Add support for frequency
invariance").

With CONFIG_ACPI_CPPC_CPUFREQ_FIE=y and schedutil cpufreq governor on
slow-switching system (like on this Ampere Altra WIWYNN Mt. Jade Arm
Server):

DL task `curr=sugov:112` lets `p=cppc_fie` migrate and since the latter
is in `non_contending` state, migrate_task_rq_dl() calls

  sub_running_bw()->__sub_running_bw()->cpufreq_update_util()->
  rq_clock()->assert_clock_updated()

on p.

Fix this by updating the clock for a non_contending task in
migrate_task_rq_dl() before calling sub_running_bw().

Reported-by: Bruno Goncalves <bgoncalv@redhat.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20210804135925.3734605-1-dietmar.eggemann@arm.com
2021-08-06 14:25:24 +02:00
Mel Gorman 56498cfb04 sched/fair: Avoid a second scan of target in select_idle_cpu
When select_idle_cpu starts scanning for an idle CPU, it starts with
a target CPU that has already been checked by select_idle_sibling.
This patch starts with the next CPU instead.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210804115857.6253-3-mgorman@techsingularity.net
2021-08-04 15:16:44 +02:00
Mel Gorman 89aafd67f2 sched/fair: Use prev instead of new target as recent_used_cpu
After select_idle_sibling, p->recent_used_cpu is set to the
new target. However on the next wakeup, prev will be the same as
recent_used_cpu unless the load balancer has moved the task since the
last wakeup. It still works, but is less efficient than it could be.
This patch preserves recent_used_cpu for longer.

The impact on SIS efficiency is tiny so the SIS statistic patches were
used to track the hit rate for using recent_used_cpu. With perf bench
pipe on a 2-socket Cascadelake machine, the hit rate went from 57.14%
to 85.32%. For more intensive wakeup loads like hackbench, the hit rate
is almost negligible but rose from 0.21% to 6.64%. For scaling loads
like tbench, the hit rate goes from almost 0% to 25.42% overall. Broadly
speaking, on tbench, the success rate is much higher for lower thread
counts and drops to almost 0 as the workload scales to towards saturation.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210804115857.6253-2-mgorman@techsingularity.net
2021-08-04 15:16:44 +02:00
Quentin Perret 7ad721bf10 sched: Don't report SCHED_FLAG_SUGOV in sched_getattr()
SCHED_FLAG_SUGOV is supposed to be a kernel-only flag that userspace
cannot interact with. However, sched_getattr() currently reports it
in sched_flags if called on a sugov worker even though it is not
actually defined in a UAPI header. To avoid this, make sure to
clean-up the sched_flags field in sched_getattr() before returning to
userspace.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210727101103.2729607-3-qperret@google.com
2021-08-04 15:16:44 +02:00
Quentin Perret f95091536f sched/deadline: Fix reset_on_fork reporting of DL tasks
It is possible for sched_getattr() to incorrectly report the state of
the reset_on_fork flag when called on a deadline task.

Indeed, if the flag was set on a deadline task using sched_setattr()
with flags (SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_KEEP_PARAMS), then
p->sched_reset_on_fork will be set, but __setscheduler() will bail out
early, which means that the dl_se->flags will not get updated by
__setscheduler_params()->__setparam_dl(). Consequently, if
sched_getattr() is then called on the task, __getparam_dl() will
override kattr.sched_flags with the now out-of-date copy in dl_se->flags
and report the stale value to userspace.

To fix this, make sure to only copy the flags that are relevant to
sched_deadline to and from the dl_se->flags field.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210727101103.2729607-2-qperret@google.com
2021-08-04 15:16:43 +02:00
Wang Hui f912d05161 sched: remove redundant on_rq status change
activate_task/deactivate_task will change on_rq status,
no need to do it again.

Signed-off-by: Wang Hui <john.wanghui@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210721091109.1406043-1-john.wanghui@huawei.com
2021-08-04 15:16:43 +02:00
Mika Penttilä 1c6829cfd3 sched/numa: Fix is_core_idle()
Use the loop variable instead of the function argument to test the
other SMT siblings for idle.

Fixes: ff7db0bf24 ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks")
Signed-off-by: Mika Penttilä <mika.penttila@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Link: https://lkml.kernel.org/r/20210722063946.28951-1-mika.penttila@gmail.com
2021-08-04 15:16:43 +02:00
Peter Zijlstra f558c2b834 sched/rt: Fix double enqueue caused by rt_effective_prio
Double enqueues in rt runqueues (list) have been reported while running
a simple test that spawns a number of threads doing a short sleep/run
pattern while being concurrently setscheduled between rt and fair class.

  WARNING: CPU: 3 PID: 2825 at kernel/sched/rt.c:1294 enqueue_task_rt+0x355/0x360
  CPU: 3 PID: 2825 Comm: setsched__13
  RIP: 0010:enqueue_task_rt+0x355/0x360
  Call Trace:
   __sched_setscheduler+0x581/0x9d0
   _sched_setscheduler+0x63/0xa0
   do_sched_setscheduler+0xa0/0x150
   __x64_sys_sched_setscheduler+0x1a/0x30
   do_syscall_64+0x33/0x40
   entry_SYSCALL_64_after_hwframe+0x44/0xae

  list_add double add: new=ffff9867cb629b40, prev=ffff9867cb629b40,
		       next=ffff98679fc67ca0.
  kernel BUG at lib/list_debug.c:31!
  invalid opcode: 0000 [#1] PREEMPT_RT SMP PTI
  CPU: 3 PID: 2825 Comm: setsched__13
  RIP: 0010:__list_add_valid+0x41/0x50
  Call Trace:
   enqueue_task_rt+0x291/0x360
   __sched_setscheduler+0x581/0x9d0
   _sched_setscheduler+0x63/0xa0
   do_sched_setscheduler+0xa0/0x150
   __x64_sys_sched_setscheduler+0x1a/0x30
   do_syscall_64+0x33/0x40
   entry_SYSCALL_64_after_hwframe+0x44/0xae

__sched_setscheduler() uses rt_effective_prio() to handle proper queuing
of priority boosted tasks that are setscheduled while being boosted.
rt_effective_prio() is however called twice per each
__sched_setscheduler() call: first directly by __sched_setscheduler()
before dequeuing the task and then by __setscheduler() to actually do
the priority change. If the priority of the pi_top_task is concurrently
being changed however, it might happen that the two calls return
different results. If, for example, the first call returned the same rt
priority the task was running at and the second one a fair priority, the
task won't be removed by the rt list (on_list still set) and then
enqueued in the fair runqueue. When eventually setscheduled back to rt
it will be seen as enqueued already and the WARNING/BUG be issued.

Fix this by calling rt_effective_prio() only once and then reusing the
return value. While at it refactor code as well for clarity. Concurrent
priority inheritance handling is still safe and will eventually converge
to a new state by following the inheritance chain(s).

Fixes: 0782e63bc6 ("sched: Handle priority boosted tasks proper in setscheduler()")
[squashed Peterz changes; added changelog]
Reported-by: Mark Simmons <msimmons@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210803104501.38333-1-juri.lelli@redhat.com
2021-08-04 15:16:31 +02:00
Linus Torvalds 877029d921 Three fixes:
- Fix load tracking bug/inconsistency
  - Fix a sporadic CFS bandwidth constraints enforcement bug
  - Fix a uclamp utilization tracking bug for newly woken tasks
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2021-07-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:
 "Three fixes:

   - Fix load tracking bug/inconsistency

   - Fix a sporadic CFS bandwidth constraints enforcement bug

   - Fix a uclamp utilization tracking bug for newly woken tasks"

* tag 'sched-urgent-2021-07-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/uclamp: Ignore max aggregation if rq is idle
  sched/fair: Fix CFS bandwidth hrtimer expiry type
  sched/fair: Sync load_sum with load_avg after dequeue
2021-07-11 11:13:57 -07:00
Linus Torvalds aef4226f91 More power management updates for 5.14-rc1
- Drop the ->stop_cpu() (not really useful) and ->resolve_freq()
    (unused) cpufreq driver callbacks and modify the users of the
    former accordingly (Viresh Kumar, Rafael Wysocki).
 
  - Add frequency invariance support to the ACPI CPPC cpufreq driver
    again along with the related fixes and cleanups (Viresh Kumar).
 
  - Update the Meditak, qcom and SCMI ARM cpufreq drivers (Fabien
    Parent, Seiya Wang, Sibi Sankar, Christophe JAILLET).
 
  - Rename black/white-lists in the DT cpufreq driver (Viresh Kumar).
 
  - Add generic performance domains support to the dvfs DT bindings
    (Sudeep Holla).
 
  - Refine locking in the generic power domains (genpd) support code
    to avoid lock dependency issues (Stephen Boyd).
 
  - Update the MSM and qcom ARM cpuidle drivers (Bartosz Dudziak).
 
  - Simplify the PM core debug code by using ktime_us_delta() to
    compute time interval lengths (Mark-PK Tsai).
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Merge tag 'pm-5.14-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull more power management updates from Rafael Wysocki:
 "These include cpufreq core simplifications and fixes, cpufreq driver
  updates, cpuidle driver update, a generic power domains (genpd)
  locking fix and a debug-related simplification of the PM core.

  Specifics:

   - Drop the ->stop_cpu() (not really useful) and ->resolve_freq()
     (unused) cpufreq driver callbacks and modify the users of the
     former accordingly (Viresh Kumar, Rafael Wysocki).

   - Add frequency invariance support to the ACPI CPPC cpufreq driver
     again along with the related fixes and cleanups (Viresh Kumar).

   - Update the Meditak, qcom and SCMI ARM cpufreq drivers (Fabien
     Parent, Seiya Wang, Sibi Sankar, Christophe JAILLET).

   - Rename black/white-lists in the DT cpufreq driver (Viresh Kumar).

   - Add generic performance domains support to the dvfs DT bindings
     (Sudeep Holla).

   - Refine locking in the generic power domains (genpd) support code to
     avoid lock dependency issues (Stephen Boyd).

   - Update the MSM and qcom ARM cpuidle drivers (Bartosz Dudziak).

   - Simplify the PM core debug code by using ktime_us_delta() to
     compute time interval lengths (Mark-PK Tsai)"

* tag 'pm-5.14-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (21 commits)
  PM: domains: Shrink locking area of the gpd_list_lock
  PM: sleep: Use ktime_us_delta() in initcall_debug_report()
  cpufreq: CPPC: Add support for frequency invariance
  arch_topology: Avoid use-after-free for scale_freq_data
  cpufreq: CPPC: Pass structure instance by reference
  cpufreq: CPPC: Fix potential memleak in cppc_cpufreq_cpu_init
  cpufreq: Remove ->resolve_freq()
  cpufreq: Reuse cpufreq_driver_resolve_freq() in __cpufreq_driver_target()
  cpufreq: Remove the ->stop_cpu() driver callback
  cpufreq: powernv: Migrate to ->exit() callback instead of ->stop_cpu()
  cpufreq: CPPC: Migrate to ->exit() callback instead of ->stop_cpu()
  cpufreq: intel_pstate: Combine ->stop_cpu() and ->offline()
  cpuidle: qcom: Add SPM register data for MSM8226
  dt-bindings: arm: msm: Add SAW2 for MSM8226
  dt-bindings: cpufreq: update cpu type and clock name for MT8173 SoC
  clk: mediatek: remove deprecated CLK_INFRA_CA57SEL for MT8173 SoC
  cpufreq: dt: Rename black/white-lists
  cpufreq: scmi: Fix an error message
  cpufreq: mediatek: add support for mt8365
  dt-bindings: dvfs: Add support for generic performance domains
  ...
2021-07-07 13:22:59 -07:00
Xuewen Yan 3e1493f463 sched/uclamp: Ignore max aggregation if rq is idle
When a task wakes up on an idle rq, uclamp_rq_util_with() would max
aggregate with rq value. But since there is no task enqueued yet, the
values are stale based on the last task that was running. When the new
task actually wakes up and enqueued, then the rq uclamp values should
reflect that of the newly woken up task effective uclamp values.

This is a problem particularly for uclamp_max because it default to
1024. If a task p with uclamp_max = 512 wakes up, then max aggregation
would ignore the capping that should apply when this task is enqueued,
which is wrong.

Fix that by ignoring max aggregation if the rq is idle since in that
case the effective uclamp value of the rq will be the ones of the task
that will wake up.

Fixes: 9d20ad7dfc ("sched/uclamp: Add uclamp_util_with()")
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
[qias: Changelog]
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Link: https://lore.kernel.org/r/20210630141204.8197-1-xuewen.yan94@gmail.com
2021-07-02 15:58:24 +02:00
Odin Ugedal 72d0ad7cb5 sched/fair: Fix CFS bandwidth hrtimer expiry type
The time remaining until expiry of the refresh_timer can be negative.
Casting the type to an unsigned 64-bit value will cause integer
underflow, making the runtime_refresh_within return false instead of
true. These situations are rare, but they do happen.

This does not cause user-facing issues or errors; other than
possibly unthrottling cfs_rq's using runtime from the previous period(s),
making the CFS bandwidth enforcement less strict in those (special)
situations.

Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al
2021-07-02 15:58:24 +02:00
Vincent Guittot ceb6ba45dc sched/fair: Sync load_sum with load_avg after dequeue
commit 9e077b52d8 ("sched/pelt: Check that *_avg are null when *_sum are")
reported some inconsitencies between *_avg and *_sum.

commit 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")
fixed some but one remains when dequeuing load.

sync the cfs's load_sum with its load_avg after dequeuing the load of a
sched_entity.

Fixes: 9e077b52d8 ("sched/pelt: Check that *_avg are null when *_sum are")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Odin Ugedal <odin@uged.al>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20210701171837.32156-1-vincent.guittot@linaro.org
2021-07-02 15:58:23 +02:00
Linus Torvalds 3dbdb38e28 Merge branch 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:

 - cgroup.kill is added which implements atomic killing of the whole
   subtree.

   Down the line, this should be able to replace the multiple userland
   implementations of "keep killing till empty".

 - PSI can now be turned off at boot time to avoid overhead for
   configurations which don't care about PSI.

* 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: make per-cgroup pressure stall tracking configurable
  cgroup: Fix kernel-doc
  cgroup: inline cgroup_task_freeze()
  tests/cgroup: test cgroup.kill
  tests/cgroup: move cg_wait_for(), cg_prepare_for_wait()
  tests/cgroup: use cgroup.kill in cg_killall()
  docs/cgroup: add entry for cgroup.kill
  cgroup: introduce cgroup.kill
2021-07-01 17:22:14 -07:00
Viresh Kumar 1eb5dde674 cpufreq: CPPC: Add support for frequency invariance
The Frequency Invariance Engine (FIE) is providing a frequency scaling
correction factor that helps achieve more accurate load-tracking.

Normally, this scaling factor can be obtained directly with the help of
the cpufreq drivers as they know the exact frequency the hardware is
running at. But that isn't the case for CPPC cpufreq driver.

Another way of obtaining that is using the arch specific counter
support, which is already present in kernel, but that hardware is
optional for platforms.

This patch updates the CPPC driver to register itself with the topology
core to provide its own implementation (cppc_scale_freq_tick()) of
topology_scale_freq_tick() which gets called by the scheduler on every
tick. Note that the arch specific counters have higher priority than
CPPC counters, if available, though the CPPC driver doesn't need to have
any special handling for that.

On an invocation of cppc_scale_freq_tick(), we schedule an irq work
(since we reach here from hard-irq context), which then schedules a
normal work item and cppc_scale_freq_workfn() updates the per_cpu
arch_freq_scale variable based on the counter updates since the last
tick.

To allow platforms to disable this CPPC counter-based frequency
invariance support, this is all done under CONFIG_ACPI_CPPC_CPUFREQ_FIE,
which is enabled by default.

This also exports sched_setattr_nocheck() as the CPPC driver can be
built as a module.

Cc: linux-acpi@vger.kernel.org
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
2021-07-01 07:32:14 +05:30
Linus Torvalds a6eaf3850c - Fix a small inconsistency (bug) in load tracking, caught by a
new warning that several people reported.
 
 - Flip CONFIG_SCHED_CORE to default-disabled, and update the
   Kconfig help text.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2021-06-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:

 - Fix a small inconsistency (bug) in load tracking, caught by a new
   warning that several people reported.

 - Flip CONFIG_SCHED_CORE to default-disabled, and update the Kconfig
   help text.

* tag 'sched-urgent-2021-06-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Disable CONFIG_SCHED_CORE by default
  sched/fair: Ensure _sum and _avg values stay consistent
2021-06-30 15:37:49 -07:00
Linus Torvalds df668a5fe4 for-5.14/block-2021-06-29
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Merge tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block

Pull core block updates from Jens Axboe:

 - disk events cleanup (Christoph)

 - gendisk and request queue allocation simplifications (Christoph)

 - bdev_disk_changed cleanups (Christoph)

 - IO priority improvements (Bart)

 - Chained bio completion trace fix (Edward)

 - blk-wbt fixes (Jan)

 - blk-wbt enable/disable fix (Zhang)

 - Scheduler dispatch improvements (Jan, Ming)

 - Shared tagset scheduler improvements (John)

 - BFQ updates (Paolo, Luca, Pietro)

 - BFQ lock inversion fix (Jan)

 - Documentation improvements (Kir)

 - CLONE_IO block cgroup fix (Tejun)

 - Remove of ancient and deprecated block dump feature (zhangyi)

 - Discard merge fix (Ming)

 - Misc fixes or followup fixes (Colin, Damien, Dan, Long, Max, Thomas,
   Yang)

* tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block: (129 commits)
  block: fix discard request merge
  block/mq-deadline: Remove a WARN_ON_ONCE() call
  blk-mq: update hctx->dispatch_busy in case of real scheduler
  blk: Fix lock inversion between ioc lock and bfqd lock
  bfq: Remove merged request already in bfq_requests_merged()
  block: pass a gendisk to bdev_disk_changed
  block: move bdev_disk_changed
  block: add the events* attributes to disk_attrs
  block: move the disk events code to a separate file
  block: fix trace completion for chained bio
  block/partitions/msdos: Fix typo inidicator -> indicator
  block, bfq: reset waker pointer with shared queues
  block, bfq: check waker only for queues with no in-flight I/O
  block, bfq: avoid delayed merge of async queues
  block, bfq: boost throughput by extending queue-merging times
  block, bfq: consider also creation time in delayed stable merge
  block, bfq: fix delayed stable merge check
  block, bfq: let also stably merged queues enjoy weight raising
  blk-wbt: make sure throttle is enabled properly
  blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled()
  ...
2021-06-30 12:12:56 -07:00