Peter Zijlstra 1cef1150ef kthread, sched/core: Fix kthread_parkme() (again...) ... Gaurav reports that commit: 85f1abe001 ("kthread, sched/wait: Fix kthread_parkme() completion issue") isn't working for him. Because of the following race: > controller Thread CPUHP Thread > takedown_cpu > kthread_park > kthread_parkme > Set KTHREAD_SHOULD_PARK > smpboot_thread_fn > set Task interruptible > > > wake_up_process > if (!(p->state & state)) > goto out; > > Kthread_parkme > SET TASK_PARKED > schedule > raw_spin_lock(&rq->lock) > ttwu_remote > waiting for __task_rq_lock > context_switch > > finish_lock_switch > > > > Case TASK_PARKED > kthread_park_complete > > > SET Running Furthermore, Oleg noticed that the whole scheduler TASK_PARKED handling is buggered because the TASK_DEAD thing is done with preemption disabled, the current code can still complete early on preemption :/ So basically revert that earlier fix and go with a variant of the alternative mentioned in the commit. Promote TASK_PARKED to special state to avoid the store-store issue on task->state leading to the WARN in kthread_unpark() -> __kthread_bind(). But in addition, add wait_task_inactive() to kthread_park() to ensure the task really is PARKED when we return from kthread_park(). This avoids the whole kthread still gets migrated nonsense -- although it would be really good to get this done differently. Reported-by: Gaurav Kohli <gkohli@codeaurora.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 85f1abe001 ("kthread, sched/wait: Fix kthread_parkme() completion issue") Signed-off-by: Ingo Molnar <mingo@kernel.org>		2018-07-03 09:17:30 +02:00
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Makefile	…
autogroup.c	sched/autogroup: Fix possible Spectre-v1 indexing for sched_prio_to_weight[]	2018-05-05 08:34:42 +02:00
autogroup.h	…
clock.c	…
completion.c	…
core.c	kthread, sched/core: Fix kthread_parkme() (again...)	2018-07-03 09:17:30 +02:00
cpuacct.c	…
cpudeadline.c	…
cpudeadline.h	…
cpufreq.c	…
cpufreq_schedutil.c	sched/rt: Fix call to cpufreq_update_util()	2018-07-03 09:17:28 +02:00
cpupri.c	…
cpupri.h	…
cputime.c	…
deadline.c	sched/deadline: Fix missing clock update	2018-05-31 12:27:13 +02:00
debug.c	proc: introduce proc_create_seq{,_data}	2018-05-16 07:23:35 +02:00
fair.c	sched/util_est: Fix util_est_dequeue() for throttled cfs_rq	2018-07-03 09:17:30 +02:00
features.h	…
idle.c	…
isolation.c	…
loadavg.c	…
membarrier.c	…
rt.c	sched/rt: Fix call to cpufreq_update_util()	2018-07-03 09:17:28 +02:00
sched-pelt.h	…
sched.h	sched/fair: Fix bandwidth timer clock drift condition	2018-07-03 09:17:29 +02:00
stats.c	proc: introduce proc_create_seq{,_data}	2018-05-16 07:23:35 +02:00
stats.h	…
stop_task.c	…
swait.c	…
topology.c	treewide: kmalloc() -> kmalloc_array()	2018-06-12 16:19:22 -07:00
wait.c	…
wait_bit.c	…