Pull cgroup hierarchy update from Tejun Heo:
"Currently, different cgroup subsystems handle nested cgroups
completely differently. There's no consistency among subsystems and
the behaviors often are outright broken.
People at least seem to agree that the broken hierarhcy behaviors need
to be weeded out if any progress is gonna be made on this front and
that the fallouts from deprecating the broken behaviors should be
acceptable especially given that the current behaviors don't make much
sense when nested.
This patch makes cgroup emit warning messages if cgroups for
subsystems with broken hierarchy behavior are nested to prepare for
fixing them in the future. This was put in a separate branch because
more related changes were expected (didn't make it this round) and the
memory cgroup wanted to pull in this and make changes on top."
* 'for-3.7-hierarchy' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them
Pull cgroup updates from Tejun Heo:
- xattr support added. The implementation is shared with tmpfs. The
usage is restricted and intended to be used to manage per-cgroup
metadata by system software. tmpfs changes are routed through this
branch with Hugh's permission.
- cgroup subsystem ID handling simplified.
* 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: Define CGROUP_SUBSYS_COUNT according the configuration
cgroup: Assign subsystem IDs during compile time
cgroup: Do not depend on a given order when populating the subsys array
cgroup: Wrap subsystem selection macro
cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT
cgroup: net_prio: Do not define task_netpioidx() when not selected
cgroup: net_cls: Do not define task_cls_classid() when not selected
cgroup: net_cls: Move sock_update_classid() declaration to cls_cgroup.h
cgroup: trivial fixes for Documentation/cgroups/cgroups.txt
xattr: mark variable as uninitialized to make both gcc and smatch happy
fs: add missing documentation to simple_xattr functions
cgroup: add documentation on extended attributes usage
cgroup: rename subsys_bits to subsys_mask
cgroup: add xattr support
cgroup: revise how we re-populate root directory
xattr: extract simple_xattr code from tmpfs
Pull workqueue changes from Tejun Heo:
"This is workqueue updates for v3.7-rc1. A lot of activities this
round including considerable API and behavior cleanups.
* delayed_work combines a timer and a work item. The handling of the
timer part has always been a bit clunky leading to confusing
cancelation API with weird corner-case behaviors. delayed_work is
updated to use new IRQ safe timer and cancelation now works as
expected.
* Another deficiency of delayed_work was lack of the counterpart of
mod_timer() which led to cancel+queue combinations or open-coded
timer+work usages. mod_delayed_work[_on]() are added.
These two delayed_work changes make delayed_work provide interface
and behave like timer which is executed with process context.
* A work item could be executed concurrently on multiple CPUs, which
is rather unintuitive and made flush_work() behavior confusing and
half-broken under certain circumstances. This problem doesn't
exist for non-reentrant workqueues. While non-reentrancy check
isn't free, the overhead is incurred only when a work item bounces
across different CPUs and even in simulated pathological scenario
the overhead isn't too high.
All workqueues are made non-reentrant. This removes the
distinction between flush_[delayed_]work() and
flush_[delayed_]_work_sync(). The former is now as strong as the
latter and the specified work item is guaranteed to have finished
execution of any previous queueing on return.
* In addition to the various bug fixes, Lai redid and simplified CPU
hotplug handling significantly.
* Joonsoo introduced system_highpri_wq and used it during CPU
hotplug.
There are two merge commits - one to pull in IRQ safe timer from
tip/timers/core and the other to pull in CPU hotplug fixes from
wq/for-3.6-fixes as Lai's hotplug restructuring depended on them."
Fixed a number of trivial conflicts, but the more interesting conflicts
were silent ones where the deprecated interfaces had been used by new
code in the merge window, and thus didn't cause any real data conflicts.
Tejun pointed out a few of them, I fixed a couple more.
* 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (46 commits)
workqueue: remove spurious WARN_ON_ONCE(in_irq()) from try_to_grab_pending()
workqueue: use cwq_set_max_active() helper for workqueue_set_max_active()
workqueue: introduce cwq_set_max_active() helper for thaw_workqueues()
workqueue: remove @delayed from cwq_dec_nr_in_flight()
workqueue: fix possible stall on try_to_grab_pending() of a delayed work item
workqueue: use hotcpu_notifier() for workqueue_cpu_down_callback()
workqueue: use __cpuinit instead of __devinit for cpu callbacks
workqueue: rename manager_mutex to assoc_mutex
workqueue: WORKER_REBIND is no longer necessary for idle rebinding
workqueue: WORKER_REBIND is no longer necessary for busy rebinding
workqueue: reimplement idle worker rebinding
workqueue: deprecate __cancel_delayed_work()
workqueue: reimplement cancel_delayed_work() using try_to_grab_pending()
workqueue: use mod_delayed_work() instead of __cancel + queue
workqueue: use irqsafe timer for delayed_work
workqueue: clean up delayed_work initializers and add missing one
workqueue: make deferrable delayed_work initializer names consistent
workqueue: cosmetic whitespace updates for macro definitions
workqueue: deprecate system_nrt[_freezable]_wq
workqueue: deprecate flush[_delayed]_work_sync()
...
As we skipped the merge window for 3.6-rc1 for the tty tree, everything
is now settled down and working properly, so we are ready for 3.7-rc1.
Here's the patchset, it's big, but the large changes are removing a
firmware file and adding a staging tty driver (it depended on the tty
core changes, so it's going through this tree instead of the staging
tree.)
All of these patches have been in the linux-next tree for a while.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull TTY changes from Greg Kroah-Hartman:
"As we skipped the merge window for 3.6-rc1 for the tty tree,
everything is now settled down and working properly, so we are ready
for 3.7-rc1. Here's the patchset, it's big, but the large changes are
removing a firmware file and adding a staging tty driver (it depended
on the tty core changes, so it's going through this tree instead of
the staging tree.)
All of these patches have been in the linux-next tree for a while.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>"
Fix up more-or-less trivial conflicts in
- drivers/char/pcmcia/synclink_cs.c:
tty NULL dereference fix vs tty_port_cts_enabled() helper function
- drivers/staging/{Kconfig,Makefile}:
add-add conflict (dgrp driver added close to other staging drivers)
- drivers/staging/ipack/devices/ipoctal.c:
"split ipoctal_channel from iopctal" vs "TTY: use tty_port_register_device"
* tag 'tty-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (235 commits)
tty/serial: Add kgdb_nmi driver
tty/serial/amba-pl011: Quiesce interrupts in poll_get_char
tty/serial/amba-pl011: Implement poll_init callback
tty/serial/core: Introduce poll_init callback
kdb: Turn KGDB_KDB=n stubs into static inlines
kdb: Implement disable_nmi command
kernel/debug: Mask KGDB NMI upon entry
serial: pl011: handle corruption at high clock speeds
serial: sccnxp: Make 'default' choice in switch last
serial: sccnxp: Remove mask termios caps for SW flow control
serial: sccnxp: Report actual baudrate back to core
serial: samsung: Add poll_get_char & poll_put_char
Powerpc 8xx CPM_UART setting MAXIDL register proportionaly to baud rate
Powerpc 8xx CPM_UART maxidl should not depend on fifo size
Powerpc 8xx CPM_UART too many interrupts
Powerpc 8xx CPM_UART desynchronisation
serial: set correct baud_base for EXSYS EX-41092 Dual 16950
serial: omap: fix the reciever line error case
8250: blacklist Winbond CIR port
8250_pnp: do pnp probe before legacy probe
...
Features currently supported:
- 39-bit address space for user and kernel (each)
- 4KB and 64KB page configurations
- Compat (32-bit) user applications (ARMv7, EABI only)
- Flattened Device Tree (mandated for all AArch64 platforms)
- ARM generic timers
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Merge tag 'arm64-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64
Pull arm64 support from Catalin Marinas:
"Linux support for the 64-bit ARM architecture (AArch64)
Features currently supported:
- 39-bit address space for user and kernel (each)
- 4KB and 64KB page configurations
- Compat (32-bit) user applications (ARMv7, EABI only)
- Flattened Device Tree (mandated for all AArch64 platforms)
- ARM generic timers"
* tag 'arm64-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64: (35 commits)
arm64: ptrace: remove obsolete ptrace request numbers from user headers
arm64: Do not set the SMP/nAMP processor bit
arm64: MAINTAINERS update
arm64: Build infrastructure
arm64: Miscellaneous header files
arm64: Generic timers support
arm64: Loadable modules
arm64: Miscellaneous library functions
arm64: Performance counters support
arm64: Add support for /proc/sys/debug/exception-trace
arm64: Debugging support
arm64: Floating point and SIMD
arm64: 32-bit (compat) applications support
arm64: User access library functions
arm64: Signal handling support
arm64: VDSO support
arm64: System calls handling
arm64: ELF definitions
arm64: SMP support
arm64: DMA mapping API
...
Pull x86/asm changes from Ingo Molnar:
"The one change that stands out is the alternatives patching change
that prevents us from ever patching back instructions from SMP to UP:
this simplifies things and speeds up CPU hotplug.
Other than that it's smaller fixes, cleanups and improvements."
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86: Unspaghettize do_trap()
x86_64: Work around old GAS bug
x86: Use REP BSF unconditionally
x86: Prefer TZCNT over BFS
x86/64: Adjust types of temporaries used by ffs()/fls()/fls64()
x86: Drop unnecessary kernel_eflags variable on 64-bit
x86/smp: Don't ever patch back to UP if we unplug cpus
Pull scheduler changes from Ingo Molnar:
"Continued quest to clean up and enhance the cputime code by Frederic
Weisbecker, in preparation for future tickless kernel features.
Other than that, smallish changes."
Fix up trivial conflicts due to additions next to each other in arch/{x86/}Kconfig
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
cputime: Make finegrained irqtime accounting generally available
cputime: Gather time/stats accounting config options into a single menu
ia64: Reuse system and user vtime accounting functions on task switch
ia64: Consolidate user vtime accounting
vtime: Consolidate system/idle context detection
cputime: Use a proper subsystem naming for vtime related APIs
sched: cpu_power: enable ARCH_POWER
sched/nohz: Clean up select_nohz_load_balancer()
sched: Fix load avg vs. cpu-hotplug
sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW
sched: Fix nohz_idle_balance()
sched: Remove useless code in yield_to()
sched: Add time unit suffix to sched sysctl knobs
sched/debug: Limit sd->*_idx range on sysctl
sched: Remove AFFINE_WAKEUPS feature flag
s390: Remove leftover account_tick_vtime() header
cputime: Consolidate vtime handling on context switch
sched: Move cputime code to its own file
cputime: Generalize CONFIG_VIRT_CPU_ACCOUNTING
tile: Remove SD_PREFER_LOCAL leftover
...
Pull perf update from Ingo Molnar:
"Lots of changes in this cycle as well, with hundreds of commits from
over 30 contributors. Most of the activity was on the tooling side.
Higher level changes:
- New 'perf kvm' analysis tool, from Xiao Guangrong.
- New 'perf trace' system-wide tracing tool
- uprobes fixes + cleanups from Oleg Nesterov.
- Lots of patches to make perf build on Android out of box, from
Irina Tirdea
- Extend ftrace function tracing utility to be more dynamic for its
users. It allows for data passing to the callback functions, as
well as reading regs as if a breakpoint were to trigger at function
entry.
The main goal of this patch series was to allow kprobes to use
ftrace as an optimized probe point when a probe is placed on an
ftrace nop. With lots of help from Masami Hiramatsu, and going
through lots of iterations, we finally came up with a good
solution.
- Add cpumask for uncore pmu, use it in 'stat', from Yan, Zheng.
- Various tracing updates from Steve Rostedt
- Clean up and improve 'perf sched' performance by elliminating lots
of needless calls to libtraceevent.
- Event group parsing support, from Jiri Olsa
- UI/gtk refactorings and improvements from Namhyung Kim
- Add support for non-tracepoint events in perf script python, from
Feng Tang
- Add --symbols to 'script', similar to the one in 'report', from
Feng Tang.
Infrastructure enhancements and fixes:
- Convert the trace builtins to use the growing evsel/evlist
tracepoint infrastructure, removing several open coded constructs
like switch like series of strcmp to dispatch events, etc.
Basically what had already been showcased in 'perf sched'.
- Add evsel constructor for tracepoints, that uses libtraceevent just
to parse the /format events file, use it in a new 'perf test' to
make sure the libtraceevent format parsing regressions can be more
readily caught.
- Some strange errors were happening in some builds, but not on the
next, reported by several people, problem was some parser related
files, generated during the build, didn't had proper make deps, fix
from Eric Sandeen.
- Introduce struct and cache information about the environment where
a perf.data file was captured, from Namhyung Kim.
- Fix handling of unresolved samples when --symbols is used in
'report', from Feng Tang.
- Add union member access support to 'probe', from Hyeoncheol Lee.
- Fixups to die() removal, from Namhyung Kim.
- Render fixes for the TUI, from Namhyung Kim.
- Don't enable annotation in non symbolic view, from Namhyung Kim.
- Fix pipe mode in 'report', from Namhyung Kim.
- Move related stats code from stat to util/, will be used by the
'stat' kvm tool, from Xiao Guangrong.
- Remove die()/exit() calls from several tools.
- Resolve vdso callchains, from Jiri Olsa
- Don't pass const char pointers to basename, so that we can
unconditionally use libgen.h and thus avoid ifdef BIONIC lines,
from David Ahern
- Refactor hist formatting so that it can be reused with the GTK
browser, From Namhyung Kim
- Fix build for another rbtree.c change, from Adrian Hunter.
- Make 'perf diff' command work with evsel hists, from Jiri Olsa.
- Use the only field_sep var that is set up: symbol_conf.field_sep,
fix from Jiri Olsa.
- .gitignore compiled python binaries, from Namhyung Kim.
- Get rid of die() in more libtraceevent places, from Namhyung Kim.
- Rename libtraceevent 'private' struct member to 'priv' so that it
works in C++, from Steven Rostedt
- Remove lots of exit()/die() calls from tools so that the main perf
exit routine can take place, from David Ahern
- Fix x86 build on x86-64, from David Ahern.
- {int,str,rb}list fixes from Suzuki K Poulose
- perf.data header fixes from Namhyung Kim
- Allow user to indicate objdump path, needed in cross environments,
from Maciek Borzecki
- Fix hardware cache event name generation, fix from Jiri Olsa
- Add round trip test for sw, hw and cache event names, catching the
problem Jiri fixed, after Jiri's patch, the test passes
successfully.
- Clean target should do clean for lib/traceevent too, fix from David
Ahern
- Check the right variable for allocation failure, fix from Namhyung
Kim
- Set up evsel->tp_format regardless of evsel->name being set
already, fix from Namhyung Kim
- Oprofile fixes from Robert Richter.
- Remove perf_event_attr needless version inflation, from Jiri Olsa
- Introduce libtraceevent strerror like error reporting facility,
from Namhyung Kim
- Add pmu mappings to perf.data header and use event names from cmd
line, from Robert Richter
- Fix include order for bison/flex-generated C files, from Ben
Hutchings
- Build fixes and documentation corrections from David Ahern
- Assorted cleanups from Robert Richter
- Let O= makes handle relative paths, from Steven Rostedt
- perf script python fixes, from Feng Tang.
- Initial bash completion support, from Frederic Weisbecker
- Allow building without libelf, from Namhyung Kim.
- Support DWARF CFI based unwind to have callchains when %bp based
unwinding is not possible, from Jiri Olsa.
- Symbol resolution fixes, while fixing support PPC64 files with an
.opt ELF section was the end goal, several fixes for code that
handles all architectures and cleanups are included, from Cody
Schafer.
- Assorted fixes for Documentation and build in 32 bit, from Robert
Richter
- Cache the libtraceevent event_format associated to each evsel
early, so that we avoid relookups, i.e. calling pevent_find_event
repeatedly when processing tracepoint events.
[ This is to reduce the surface contact with libtraceevents and
make clear what is that the perf tools needs from that lib: so
far parsing the common and per event fields. ]
- Don't stop the build if the audit libraries are not installed, fix
from Namhyung Kim.
- Fix bfd.h/libbfd detection with recent binutils, from Markus
Trippelsdorf.
- Improve warning message when libunwind devel packages not present,
from Jiri Olsa"
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (282 commits)
perf trace: Add aliases for some syscalls
perf probe: Print an enum type variable in "enum variable-name" format when showing accessible variables
perf tools: Check libaudit availability for perf-trace builtin
perf hists: Add missing period_* fields when collapsing a hist entry
perf trace: New tool
perf evsel: Export the event_format constructor
perf evsel: Introduce rawptr() method
perf tools: Use perf_evsel__newtp in the event parser
perf evsel: The tracepoint constructor should store sys:name
perf evlist: Introduce set_filter() method
perf evlist: Renane set_filters method to apply_filters
perf test: Add test to check we correctly parse and match syscall open parms
perf evsel: Handle endianity in intval method
perf evsel: Know if byte swap is needed
perf tools: Allow handling a NULL cpu_map as meaning "all cpus"
perf evsel: Improve tracepoint constructor setup
tools lib traceevent: Fix error path on pevent_parse_event
perf test: Fix build failure
trace: Move trace event enable from fs_initcall to core_initcall
tracing: Add an option for disabling markers
...
Pull core locking changes from Ingo Molnar:
"It includes a lockdep improvement plus a spinlock inlining Kconfig
cleanup."
* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking: Adjust spin lock inlining Kconfig options
lockdep: Check if nested lock is actually held
Pull core kernel fixes from Ingo Molnar:
"This is a complex task_work series from Oleg that fixes the bug that
this VFS commit tried to fix:
d35abdb288 hold task_lock around checks in keyctl
but solves the problem without the lockup regression that d35abdb288
introduced in v3.6.
This series came late in v3.6 and I did not feel confident about it so
late in the cycle. Might be worth backporting to -stable if it proves
itself upstream."
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
task_work: Simplify the usage in ptrace_notify() and get_signal_to_deliver()
task_work: Revert "hold task_lock around checks in keyctl"
task_work: task_work_add() should not succeed after exit_task_work()
task_work: Make task_work_add() lockless
Make default just return 0. The current default (checking
TIF_POLLING_NRFLAG) is taken to architectures that need it;
ones that don't do polling in their idle threads don't need
to defined TIF_POLLING_NRFLAG at all.
ia64 defined both TS_POLLING (used by its tsk_is_polling())
and TIF_POLLING_NRFLAG (not used at all). Killed the latter...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Let architectures select GENERIC_KERNEL_THREAD and have their copy_thread()
treat NULL regs as "it came from kernel_thread(), sp argument contains
the function new thread will be calling and stack_size - the argument for
that function". Switching the architectures begins shortly...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
After the previous change is_swbp_at_addr() is always called with
current->mm. Remove this check and move it close to its single caller.
Also, remove the obsolete comment about is_swbp_at_addr() and
uprobe_state.count.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Unlike set_swbp(), set_orig_insn()->is_swbp_at_addr() makes sense,
although it can't prevent all confusions.
But the usage of is_swbp_at_addr() is equally confusing, and it adds
the extra get_user_pages() we can avoid.
This patch removes set_orig_insn()->is_swbp_at_addr() but changes
write_opcode() to do the necessary checks before replace_page().
Perhaps it also makes sense to ensure PAGE_MAPPING_ANON in unregister
case.
find_active_uprobe() becomes the only user of is_swbp_at_addr(),
we can change its semantics.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
No functional changes, preparations.
1. Extract the kmap-and-memcpy code from read_opcode() into the
new trivial helper, copy_opcode(). The next patch will add
another user.
2. read_opcode() becomes really trivial, fold it into its single
caller, is_swbp_at_addr().
3. Remove "auprobe" argument from write_opcode(), it is not used
since f403072c6.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
A separate patch for better documentation.
set_swbp()->is_swbp_at_addr() is not needed for correctness, it is
harmless to do the unnecessary __replace_page(old_page, new_page)
when these 2 pages are identical.
And it can not be counted as optimization. mmap/register races are
very unlikely, while in the likely case is_swbp_at_addr() adds the
extra get_user_pages() even if the caller is uprobe_mmap(current->mm)
and returns false.
Note also that the semantics/usage of is_swbp_at_addr() in uprobe.c
is confusing. set_swbp() uses it to detect the case when this insn
was already modified by uprobes, that is why it should always compare
the opcode with UPROBE_SWBP_INSN even if the hardware (like powerpc)
has other trap insns. It doesn't matter if this breakpoint was in fact
installed by gdb or application itself, we are going to "steal" this
breakpoint anyway and execute the original insn from vm_file even if
it no longer matches the memory.
OTOH, handle_swbp()->find_active_uprobe() uses is_swbp_at_addr() to
figure out whether we need to send SIGTRAP or not if we can not find
uprobe, so in this case it should return true for all trap variants,
not only for UPROBE_SWBP_INSN.
This patch removes set_swbp()->is_swbp_at_addr(), the next patches
will remove it from set_orig_insn() which is similar to set_swbp()
in this respect. So the only caller will be handle_swbp() and we
can make its semantics clear.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
valid_vma(false) ignores ->vm_flags, this is not actually right.
We should never try to write into MAP_SHARED mapping, this can
confuse an apllication which actually writes to ->vm_file.
With this patch valid_vma(false) ignores VM_WRITE only but checks
other (immutable) bits checked by valid_vma(true). This can also
speedup uprobe_munmap() and uprobe_unregister().
Note: even after this patch _unregister can confuse the probed
application if it does mprotect(PROT_WRITE) after _register and
installs "int3", but this is hardly possible to avoid and this
doesn't differ from gdb case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
uprobe_register() or uprobe_mmap() requires VM_READ | VM_EXEC, this
is not right. An apllication can do mprotect(PROT_EXEC) later and
execute this code.
Change valid_vma(is_register => true) to check VM_MAYEXEC instead.
No need to check VM_MAYREAD, it is always set.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
write_opcode()->get_user_pages() needs FOLL_FORCE to ensure we can
read the page even if the probed task did mprotect(PROT_NONE) after
uprobe_register(). Without FOLL_WRITE, FOLL_FORCE doesn't have any
side effect but allows to read the !VM_READ memory.
Otherwiese the subsequent uprobe_unregister()->set_orig_insn() fails
and we leak "int3". If that task does mprotect(PROT_READ | EXEC) and
execute the probed insn later it will be killed.
Note: in fact this is also needed for _register, see the next patch.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Kill UTASK_BP_HIT state, it buys nothing but complicates the code.
It is only used in uprobe_notify_resume() to decide who should be
called, we can check utask->active_uprobe != NULL instead. And this
allows us to simplify handle_swbp(), no need to clear utask->state.
Likewise we could kill UTASK_SSTEP, but UTASK_BP_HIT is worse and
imho should die. The problem is, it creates the special case when
task->utask is NULL, we can't distinguish RUNNING and BP_HIT. With
this patch utask == NULL always means RUNNING.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
If handle_swbp()->add_utask() fails but UPROBE_SKIP_SSTEP is set,
cleanup_ret: path do not restart the insn, this is wrong. Remove
this check and add the additional label for can_skip_sstep() = T
case.
Note also that UPROBE_SKIP_SSTEP can be false positive, we simply
can not trust it unless arch_uprobe_skip_sstep() was already called.
Also, move another UPROBE_SKIP_SSTEP check before can_skip_sstep()
into this helper, this looks more clean and understandable.
Note: probably we should rename "skip" to "emulate" and I think
that "clear UPROBE_SKIP_SSTEP" should be moved to arch_can_skip.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
handle_swbp() sets utask->active_uprobe before handler_chain(),
and UTASK_SSTEP before pre_ssout(). This complicates the code
for no reason, arch_ hooks or consumer->handler() should not
(and can't) use this info.
Change handle_swbp() to initialize them after pre_ssout(), and
remove the no longer needed cleanup-utask code.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
cked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
If handle_swbp()->find_active_uprobe() fails we return with
utask->state = UTASK_BP_HIT.
Change handle_swbp() to reset utask->state at the start. Note
that we do this unconditionally, see the next patch(es).
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Conflicts:
drivers/net/team/team.c
drivers/net/usb/qmi_wwan.c
net/batman-adv/bat_iv_ogm.c
net/ipv4/fib_frontend.c
net/ipv4/route.c
net/l2tp/l2tp_netlink.c
The team, fib_frontend, route, and l2tp_netlink conflicts were simply
overlapping changes.
qmi_wwan and bat_iv_ogm were of the "use HEAD" variety.
With help from Antonio Quartulli.
Signed-off-by: David S. Miller <davem@davemloft.net>
Use generic steal operation on pipe buffer to allow stealing
ring buffer's read page from pipe buffer.
Note that this could reduce the performance of splice on the
splice_write side operation without affinity setting.
Since the ring buffer's read pages are allocated on the
tracing-node, but the splice user does not always execute
splice write side operation on the same node. In this case,
the page will be accessed from the another node.
Thus, it is strongly recommended to assign the splicing
thread to corresponding node.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
The original module-init-tools module loader used a fnctl lock on the
.ko file to avoid attempts to simultaneously load a module.
Unfortunately, you can't get an exclusive fcntl lock on a read-only
fd, making this not work for read-only mounted filesystems.
module-init-tools has a hacky sleep-and-loop for this now.
It's not that hard to wait in the kernel, and only return -EEXIST once
the first module has finished loading (or continue loading the module
if the first one failed to initialize for some reason). It's also
consistent with what we do for dependent modules which are still loading.
Suggested-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We use resolve_symbol_wait(), which blocks if the module containing
the symbol is still loading. However:
1) The module_wq we use is only woken after calling the modules' init
function, but there are other failure paths after the module is
placed in the linked list where we need to do the same thing.
2) wake_up() only wakes one waiter, and our waitqueue is shared by all
modules, so we need to wake them all.
3) wake_up_all() doesn't imply a memory barrier: I feel happier calling
it after we've grabbed and dropped the module_mutex, not just after
the state assignment.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Use the mapping of Elf_[SPE]hdr, Elf_Addr, Elf_Sym, Elf_Dyn, Elf_Rel/Rela,
ELF_R_TYPE() and ELF_R_SYM() to either the 32-bit version or the 64-bit version
into asm-generic/module.h for all arches bar MIPS.
Also, use the generic definition mod_arch_specific where possible.
To this end, I've defined three new config bools:
(*) HAVE_MOD_ARCH_SPECIFIC
Arches define this if they don't want to use the empty generic
mod_arch_specific struct.
(*) MODULES_USE_ELF_RELA
Arches define this if their modules can contain RELA records. This causes
the Elf_Rela mapping to be emitted and allows apply_relocate_add() to be
defined by the arch rather than have the core emit an error message.
(*) MODULES_USE_ELF_REL
Arches define this if their modules can contain REL records. This causes
the Elf_Rel mapping to be emitted and allows apply_relocate() to be
defined by the arch rather than have the core emit an error message.
Note that it is possible to allow both REL and RELA records: m68k and mips are
two arches that do this.
With this, some arch asm/module.h files can be deleted entirely and replaced
with a generic-y marker in the arch Kbuild file.
Additionally, I have removed the bits from m32r and score that handle the
unsupported type of relocation record as that's now handled centrally.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cloudlinux have a product called lve that includes a kernel module. This
was previously GPLed but is now under a proprietary license, but the
module continues to declare MODULE_LICENSE("GPL") and makes use of some
EXPORT_SYMBOL_GPL symbols. Forcibly taint it in order to avoid this.
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Alex Lyashkov <umka@cloudlinux.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org
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Merge tag 'v3.6-rc7' into next
Linux 3.6-rc7
Requested by David Howells so he can merge his key susbsystem work into
my tree with requisite -linus changesets.
descriptor-related parts of daemonize, done right. As the
result we simplify the locking rules for ->files - we
hold task_lock in *all* cases when we modify ->files.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This command disables NMI-entry. If NMI source has been previously shared
with a serial console ("debug port"), this effectively releases the port
from KDB exclusive use, and makes the console available for normal use.
Of course, NMI can be reenabled, enable_nmi modparam is used for that:
echo 1 > /sys/module/kdb/parameters/enable_nmi
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The new arch callback should manage NMIs that usually cause KGDB to
enter. That is, not all NMIs should be enabled/disabled, but only
those that issue kgdb_handle_exception().
We must mask it as serial-line interrupt can be used as an NMI, so
if the original KGDB-entry cause was say a breakpoint, then every
input to KDB console will cause KGDB to reenter, which we don't want.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Checking "user" before "is_idle_task()" allows better optimizations
in cases where inlining is possible. Also, "bool" should be passed
"true" or "false" rather than "1" or "0". This commit therefore makes
these changes, as noted in Josh's review.
Reported-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Provide a config option that enables the userspace
RCU extended quiescent state on every CPUs by default.
This is for testing purpose.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
When exceptions or irq are about to resume userspace, if
the task needs to be rescheduled, the arch low level code
calls schedule() directly.
If we call it, it is because we have the TIF_RESCHED flag:
- It can be set after random local calls to set_need_resched()
(RCU, drm, ...)
- A wake up happened and the CPU needs preemption. This can
happen in several ways:
* Remotely: the remote waking CPU has set TIF_RESCHED and send the
wakee an IPI to schedule the new task.
* Remotely enqueued: the remote waking CPU sends an IPI to the target
and the wake up is made by the target.
* Locally: waking CPU == wakee CPU and the wakeup is done locally.
set_need_resched() is called without IPI.
In the case of local and remotely enqueued wake ups, the tick can
be restarted when we enqueue the new task and RCU can exit the
extended quiescent state at the same time. Then by the time we reach
irq exit path and we call schedule, we are not in RCU user mode.
But if we call schedule() only because something called set_need_resched(),
RCU may still be in user mode when we reach schedule.
Also if a wake up is done remotely, the CPU might see the TIF_RESCHED
flag and call schedule while the IPI has not yet happen to restart the
tick and exit RCU user mode.
We need to manually protect against these corner cases.
Create a new API schedule_user() that calls schedule() inside
rcu_user_exit()-rcu_user_enter() in order to protect it. Archs
will need to rely on it now to implement user preemption safely.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
When an exception or an irq exits, and we are going to resume into
interrupted kernel code, the low level architecture code calls
preempt_schedule_irq() if there is a need to reschedule.
If the interrupt/exception occured between a call to rcu_user_enter()
(from syscall exit, exception exit, do_notify_resume exit, ...) and
a real resume to userspace (iret,...), preempt_schedule_irq() can be
called whereas RCU thinks we are in userspace. But preempt_schedule_irq()
is going to run kernel code and may be some RCU read side critical
section. We must exit the userspace extended quiescent state before
we call it.
To solve this, just call rcu_user_exit() in the beginning of
preempt_schedule_irq().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Clear the syscalls hook of a task when it's scheduled out so that if
the task migrates, it doesn't run the syscall slow path on a CPU
that might not need it.
Also set the syscalls hook on the next task if needed.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
By default we don't want to enter into RCU extended quiescent
state while in userspace because doing this produces some overhead
(eg: use of syscall slowpath). Set it off by default and ready to
run when some feature like adaptive tickless need it.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Allow calls to rcu_user_enter() even if we are already
in userspace (as seen by RCU) and allow calls to rcu_user_exit()
even if we are already in the kernel.
This makes the APIs more flexible to be called from architectures.
Exception entries for example won't need to know if they come from
userspace before calling rcu_user_exit().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Create a new config option under the RCU menu that put
CPUs under RCU extended quiescent state (as in dynticks
idle mode) when they run in userspace. This require
some contribution from architectures to hook into kernel
and userspace boundaries.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The current implementation of RCU_FAST_NO_HZ tries reasonably hard to rid
the current CPU of RCU callbacks. This is appropriate when the CPU is
entering idle, where it doesn't have much useful to do anyway, but is most
definitely not what you want when transitioning to user-mode execution.
This commit therefore detects the adaptive-tick case, and refrains from
burning CPU time getting rid of RCU callbacks in that case.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
In some cases, it is necessary to enter or exit userspace-RCU-idle mode
from an interrupt handler, for example, if some other CPU sends this
CPU a resched IPI. In this case, the current CPU would enter the IPI
handler in userspace-RCU-idle mode, but would need to exit the IPI handler
after having exited that mode.
To allow this to work, this commit adds two new APIs to TREE_RCU:
- rcu_user_enter_after_irq(). This must be called from an interrupt between
rcu_irq_enter() and rcu_irq_exit(). After the irq calls rcu_irq_exit(),
the irq handler will return into an RCU extended quiescent state.
In theory, this interrupt is never a nested interrupt, but in practice
it might interrupt softirq, which looks to RCU like a nested interrupt.
- rcu_user_exit_after_irq(). This must be called from a non-nesting
interrupt, interrupting an RCU extended quiescent state, also
between rcu_irq_enter() and rcu_irq_exit(). After the irq calls
rcu_irq_exit(), the irq handler will return in an RCU non-quiescent
state.
[ Combined with "Allow calls to rcu_exit_user_irq from nesting irqs." ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
RCU currently insists that only idle tasks can enter RCU idle mode, which
prohibits an adaptive tickless kernel (AKA nohz cpusets), which in turn
would mean that usermode execution would always take scheduling-clock
interrupts, even when there is only one task runnable on the CPU in
question.
This commit therefore adds rcu_user_enter() and rcu_user_exit(), which
allow non-idle tasks to enter RCU idle mode. These are quite similar
to rcu_idle_enter() and rcu_idle_exit(), respectively, except that they
omit the idle-task checks.
[ Updated to use "user" flag rather than separate check functions. ]
[ paulmck: Updated to drop exports of new functions based on Josh's patch
getting rid of the need for them. ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The conflicts between kernel/rcutree.h and kernel/rcutree_plugin.h
were due to adjacent insertions and deletions, which were resolved
by simply accepting the changes on both branches.
Move the code that finds out to which context we account the
cputime into generic layer.
Archs that consider the whole time spent in the idle task as idle
time (ia64, powerpc) can rely on the generic vtime_account()
and implement vtime_account_system() and vtime_account_idle(),
letting the generic code to decide when to call which API.
Archs that have their own meaning of idle time, such as s390
that only considers the time spent in CPU low power mode as idle
time, can just override vtime_account().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Use a naming based on vtime as a prefix for virtual based
cputime accounting APIs:
- account_system_vtime() -> vtime_account()
- account_switch_vtime() -> vtime_task_switch()
It makes it easier to allow for further declension such
as vtime_account_system(), vtime_account_idle(), ... if we
want to find out the context we account to from generic code.
This also make it better to know on which subsystem these APIs
refer to.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
bigrt.2012.09.23a contains additional commits to reduce scheduling latency
from RCU on huge systems (many hundrends or thousands of CPUs).
doctorture.2012.09.23a contains documentation changes and rcutorture fixes.
fixes.2012.09.23a contains miscellaneous fixes.
hotplug.2012.09.23a contains CPU-hotplug-related changes.
idle.2012.09.23a fixes architectures for which RCU no longer considered
the idle loop to be a quiescent state due to earlier
adaptive-dynticks changes. Affected architectures are alpha,
cris, frv, h8300, m32r, m68k, mn10300, parisc, score, xtensa,
and ia64.
We currently use a per socket order-0 page cache for tcp_sendmsg()
operations.
This page is used to build fragments for skbs.
Its done to increase probability of coalescing small write() into
single segments in skbs still in write queue (not yet sent)
But it wastes a lot of memory for applications handling many mostly
idle sockets, since each socket holds one page in sk->sk_sndmsg_page
Its also quite inefficient to build TSO 64KB packets, because we need
about 16 pages per skb on arches where PAGE_SIZE = 4096, so we hit
page allocator more than wanted.
This patch adds a per task frag allocator and uses bigger pages,
if available. An automatic fallback is done in case of memory pressure.
(up to 32768 bytes per frag, thats order-3 pages on x86)
This increases TCP stream performance by 20% on loopback device,
but also benefits on other network devices, since 8x less frags are
mapped on transmit and unmapped on tx completion. Alexander Duyck
mentioned a probable performance win on systems with IOMMU enabled.
Its possible some SG enabled hardware cant cope with bigger fragments,
but their ndo_start_xmit() should already handle this, splitting a
fragment in sub fragments, since some arches have PAGE_SIZE=65536
Successfully tested on various ethernet devices.
(ixgbe, igb, bnx2x, tg3, mellanox mlx4)
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Vijay Subramanian <subramanian.vijay@gmail.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch splits trace event initialization in two stages:
* ftrace enable
* sysfs event entry creation
This allows to capture trace events from an earlier point
by using 'trace_event' kernel parameter and is important
to trace boot-up allocations.
Note that, in order to enable events at core_initcall,
it's necessary to move init_ftrace_syscalls() from
core_initcall to early_initcall.
Link: http://lkml.kernel.org/r/1347461277-25302-1-git-send-email-elezegarcia@gmail.com
Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
In our application, we have trace markers spread through user-space.
We have markers in GL, X, etc. These are super handy for Chrome's
about:tracing feature (Chrome + system + kernel trace view), but
can be very distracting when you're trying to debug a kernel issue.
I normally, use "grep -v tracing_mark_write" but it would be nice
if I could just temporarily disable markers all together.
Link: http://lkml.kernel.org/r/1347066739-26285-1-git-send-email-msb@chromium.org
CC: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
We only do rounding to the next nanosecond so we don't see minor
1ns inconsistencies in the vsyscall implementations. Since we're
changing the vsyscall implementations to avoid this, conditionalize
the rounding only to the GENERIC_TIME_VSYSCALL_OLD architectures.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Now that we moved everyone over to GENERIC_TIME_VSYSCALL_OLD,
introduce the new declaration and config option for the new
update_vsyscall method.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
To help migrate archtectures over to the new update_vsyscall method,
redfine CONFIG_GENERIC_TIME_VSYSCALL as CONFIG_GENERIC_TIME_VSYSCALL_OLD
Cc: Tony Luck <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Since users will need to include timekeeper_internal.h, move
update_vsyscall definitions to timekeeper_internal.h.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
We're going to need to access the timekeeper in update_vsyscall,
so make the structure available for those who need it.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
CLOCK_TICK_RATE is used to accurately caclulate exactly how
a tick will be at a given HZ.
This is useful, because while we'd expect NSEC_PER_SEC/HZ,
the underlying hardware will have some granularity limit,
so we won't be able to have exactly HZ ticks per second.
This slight error can cause timekeeping quality problems
when using the jiffies or other jiffies driven clocksources.
Thus we currently use compile time CLOCK_TICK_RATE value to
generate SHIFTED_HZ and NSEC_PER_JIFFIES, which we then use
to adjust the jiffies clocksource to correct this error.
Unfortunately though, since CLOCK_TICK_RATE is a compile
time value, and the jiffies clocksource is registered very
early during boot, there are a number of cases where there
are different possible hardware timers that have different
tick rates. This causes problems in cases like ARM where
there are numerous different types of hardware, each having
their own compile-time CLOCK_TICK_RATE, making it hard to
accurately support different hardware with a single kernel.
For the most part, this doesn't matter all that much, as not
too many systems actually utilize the jiffies or jiffies driven
clocksource. Usually there are other highres clocksources
who's granularity error is negligable.
Even so, we have some complicated calcualtions that we do
everywhere to handle these edge cases.
This patch removes the compile time SHIFTED_HZ value, and
introduces a register_refined_jiffies() function. This results
in the default jiffies clock as being assumed a perfect HZ
freq, and allows archtectures that care about jiffies accuracy
to call register_refined_jiffies() with the tick rate, specified
dynamically at boot.
This allows us, where necessary, to not have a compile time
CLOCK_TICK_RATE constant, simplifies the jiffies code, and
still provides a way to have an accurate jiffies clock.
NOTE: Since this patch does not add register_refinied_jiffies()
calls for every arch, it may cause time quality regressions
in some cases. Its likely these will not be noticable, but
if they are an issue, adding the following to the end of
setup_arch() should resolve the regression:
register_refinied_jiffies(CLOCK_TICK_RATE)
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Now that alarmtimer_remove has been simplified, change
its name to _dequeue to better match its paired _enqueue
function.
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Colin Cross <ccross@android.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Arve Hjønnevåg reported numerous crashes from the
"BUG_ON(timer->state != HRTIMER_STATE_CALLBACK)" check
in __run_hrtimer after it called alarmtimer_fired.
It ends up the alarmtimer code was not properly handling
possible failures of hrtimer_try_to_cancel, and because
these faulres occur when the underlying base hrtimer is
being run, this limits the ability to properly handle
modifications to any alarmtimers on that base.
Because much of the logic duplicates the hrtimer logic,
it seems that we might as well have a per-alarmtimer
hrtimer, and avoid the extra complextity of trying to
multiplex many alarmtimers off of one hrtimer.
Thus this patch moves the hrtimer to the alarm structure
and simplifies the management logic.
Changelog:
v2:
* Includes a fix for double alarm_start calls found by
Arve
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Colin Cross <ccross@android.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Arve Hjønnevåg <arve@android.com>
Tested-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
alarmtimer suspend return -EBUSY if the next alarm will fire in less
than 2 seconds. This allows one RTC seconds tick to occur subsequent
to this check before the alarm wakeup time is set, ensuring the wakeup
time is still in the future (assuming the RTC does not tick one more
second prior to setting the alarm).
If suspend is rejected due to an imminent alarm, hold a wakeup source
for 2 seconds to process the alarm prior to reattempting suspend.
If setting the alarm incurs an -ETIME for an alarm set in the past,
or any other problem setting the alarm, abort suspend and hold a
wakelock for 1 second while the alarm is allowed to be serviced or
other hopefully transient conditions preventing the alarm clear up.
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Rabik and Paul reported two different issues related to the same few
lines of code.
Rabik's issue is that the nr_uninterruptible migration code is wrong in
that he sees artifacts due to this (Rabik please do expand in more
detail).
Paul's issue is that this code as it stands relies on us using
stop_machine() for unplug, we all would like to remove this assumption
so that eventually we can remove this stop_machine() usage altogether.
The only reason we'd have to migrate nr_uninterruptible is so that we
could use for_each_online_cpu() loops in favour of
for_each_possible_cpu() loops, however since nr_uninterruptible() is the
only such loop and its using possible lets not bother at all.
The problem Rabik sees is (probably) caused by the fact that by
migrating nr_uninterruptible we screw rq->calc_load_active for both rqs
involved.
So don't bother with fancy migration schemes (meaning we now have to
keep using for_each_possible_cpu()) and instead fold any nr_active delta
after we migrate all tasks away to make sure we don't have any skewed
nr_active accounting.
[ paulmck: Move call to calc_load_migration to CPU_DEAD to avoid
miscounting noted by Rakib. ]
Reported-by: Rakib Mullick <rakib.mullick@gmail.com>
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Posting a callback after the CPU_DEAD notifier effectively leaks
that callback unless/until that CPU comes back online. Silence is
unhelpful when attempting to track down such leaks, so this commit emits
a WARN_ON_ONCE() and unconditionally leaks the callback when an offline
CPU attempts to register a callback. The rdp->nxttail[RCU_NEXT_TAIL] is
set to NULL in the CPU_DEAD notifier and restored in the CPU_UP_PREPARE
notifier, allowing _call_rcu() to determine exactly when posting callbacks
is illegal.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Currently, _rcu_barrier() relies on preempt_disable() to prevent
any CPU from going offline, which in turn depends on CPU hotplug's
use of __stop_machine().
This patch therefore makes _rcu_barrier() use get_online_cpus() to
block CPU-hotplug operations. This has the added benefit of removing
the need for _rcu_barrier() to adopt callbacks: Because CPU-hotplug
operations are excluded, there can be no callbacks to adopt. This
commit simplifies the code accordingly.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The print_cpu_stall_fast_no_hz() function attempts to print -1 when
the ->idle_gp_timer is not pending, but unsigned arithmetic causes it
to instead print ULONG_MAX, which is 4294967295 on 32-bit systems and
18446744073709551615 on 64-bit systems. Neither of these are the most
reader-friendly values, so this commit instead causes "timer not pending"
to be printed when ->idle_gp_timer is not pending.
Reported-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
TINY_RCU's rcu_idle_enter_common() invokes rcu_sched_qs() in order
to inform the RCU core of the quiescent state implied by idle entry.
Of course, idle is also an extended quiescent state, so that the call
to rcu_sched_qs() speeds up RCU's invoking of any callbacks that might
be queued. This speed-up is important when entering into dyntick-idle
mode -- if there are no further scheduling-clock interrupts, the callbacks
might never be invoked, which could result in a system hang.
However, processing callbacks does event tracing, which in turn
implies RCU read-side critical sections, which are illegal in extended
quiescent states. This patch therefore moves the call to rcu_sched_qs()
so that it precedes the point at which we inform lockdep that RCU has
entered an extended quiescent state.
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The can_stop_idle_tick() function complains if a softirq vector is
raised too late in the idle-entry process, presumably in order to
prevent dangling softirq invocations from being delayed across the
full idle period, which might be indefinitely long -- and if softirq
was asserted any later than the call to this function, such a delay
might well happen.
However, RCU needs to be able to use softirq to stop idle entry in
order to be able to drain RCU callbacks from the current CPU, which in
turn enables faster entry into dyntick-idle mode, which in turn reduces
power consumption. Because RCU takes this action at a well-defined
point in the idle-entry path, it is safe for RCU to take this approach.
This commit therefore silences the error message that is sometimes
produced when the going-idle CPU suddenly finds that it has an RCU_SOFTIRQ
to process. The error message will continue to be issued for other
softirq vectors.
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The use of raw_local_irq_save() is unnecessary, given that local_irq_save()
really does disable interrupts. Also, it appears to interfere with lockdep.
Therefore, this commit moves to local_irq_save().
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
The first memory barrier in __call_rcu() is supposed to order any
updates done beforehand by the caller against the actual queuing
of the callback. However, the second memory barrier (which is intended
to order incrementing the queue lengths before queuing the callback)
is also between the caller's updates and the queuing of the callback.
The second memory barrier can therefore serve both purposes.
This commit therefore removes the first memory barrier.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
If a given CPU avoids the idle loop but also avoids starting a new
RCU grace period for a full minute, RCU can issue spurious RCU CPU
stall warnings. This commit fixes this issue by adding a check for
ongoing grace period to avoid these spurious stall warnings.
Reported-by: Becky Bruce <bgillbruce@gmail.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The print_other_cpu_stall() function accesses a number of rcu_node
fields without protection from the ->lock. In theory, this is not
a problem because the fields accessed are all integers, but in
practice the compiler can get nasty. Therefore, the commit extends
the existing critical section to cover the entire loop body.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The rcu_print_detail_task_stall_rnp() function invokes
rcu_preempt_blocked_readers_cgp() to verify that there are some preempted
RCU readers blocking the current grace period outside of the protection
of the rcu_node structure's ->lock. This means that the last blocked
reader might exit its RCU read-side critical section and remove itself
from the ->blkd_tasks list before the ->lock is acquired, resulting in
a segmentation fault when the subsequent code attempts to dereference
the now-NULL gp_tasks pointer.
This commit therefore moves the test under the lock. This will not
have measurable effect on lock contention because this code is invoked
only when printing RCU CPU stall warnings, in other words, in the common
case, never.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The increment_cpu_stall_ticks() function listed each RCU flavor
explicitly, with an ifdef to handle preemptible RCU. This commit
therefore applies for_each_rcu_flavor() to save a line of code.
Because this commit switches from a code-based enumeration of the
flavors of RCU to an rcu_state-list-based enumeration, it is no longer
possible to apply __get_cpu_var() to the per-CPU rcu_data structures.
We instead use __this_cpu_var() on the rcu_state structure's ->rda field
that references the corresponding rcu_data structures.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Commit 1217ed1b (rcu: permit rcu_read_unlock() to be called while holding
runqueue locks) made rcu_initiate_boost() restore irq state when releasing
the rcu_node structure's ->lock, but failed to update the header comment
accordingly. This commit therefore brings the header comment up to date.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The rcu_implicit_offline_qs() function implicitly assumed that execution
would progress predictably when interrupts are disabled, which is of course
not guaranteed when running on a hypervisor. Furthermore, this function
is short, and is called from one place only in a short function.
This commit therefore ensures that the timing is checked before
checking the condition, which guarantees correct behavior even given
indefinite delays. It also inlines rcu_implicit_offline_qs() into
rcu_implicit_dynticks_qs().
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The rcu_preempt_offline_tasks() moves all tasks queued on a given leaf
rcu_node structure to the root rcu_node, which is done when the last CPU
corresponding the the leaf rcu_node structure goes offline. Now that
RCU-preempt's synchronize_rcu_expedited() implementation blocks CPU-hotplug
operations during the initialization of each rcu_node structure's
->boost_tasks pointer, rcu_preempt_offline_tasks() can do a better job
of setting the root rcu_node's ->boost_tasks pointer.
The key point is that rcu_preempt_offline_tasks() runs as part of the
CPU-hotplug process, so that a concurrent synchronize_rcu_expedited()
is guaranteed to either have not started on the one hand (in which case
there is no boosting on behalf of the expedited grace period) or to be
completely initialized on the other (in which case, in the absence of
other priority boosting, all ->boost_tasks pointers will be initialized).
Therefore, if rcu_preempt_offline_tasks() finds that the ->boost_tasks
pointer is equal to the ->exp_tasks pointer, it can be sure that it is
correctly placed.
In the case where there was boosting ongoing at the time that the
synchronize_rcu_expedited() function started, different nodes might start
boosting the tasks blocking the expedited grace period at different times.
In this mixed case, the root node will either be boosting tasks for
the expedited grace period already, or it will start as soon as it gets
done boosting for the normal grace period -- but in this latter case,
the root node's tasks needed to be boosted in any case.
This commit therefore adds a check of the ->boost_tasks pointer against
the ->exp_tasks pointer to the list that prevents updating ->boost_tasks.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
There is a need to use RCU from interrupt context, but either before
rcu_irq_enter() is called or after rcu_irq_exit() is called. If the
interrupt occurs from idle, then lockdep-RCU will complain about such
uses, as they appear to be illegal uses of RCU from the idle loop.
In other environments, RCU_NONIDLE() could be used to properly protect
the use of RCU, but RCU_NONIDLE() currently cannot be invoked except
from process context.
This commit therefore modifies RCU_NONIDLE() to permit its use more
globally.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
When rcu_preempt_offline_tasks() clears tasks from a leaf rcu_node
structure, it does not NULL out the structure's ->boost_tasks field.
This commit therefore fixes this issue.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Because TINY_RCU's idle detection keys directly off of the nesting
level, rather than from a separate variable as in TREE_RCU, the
TINY_RCU dyntick-idle tracing on transition to idle must happen
before the change to the nesting level. This commit therefore makes
this change by passing the desired new value (rather than the old value)
of the nesting level in to rcu_idle_enter_common().
[ paulmck: Add fix for wrong-variable bug spotted by
Michael Wang <wangyun@linux.vnet.ibm.com>. ]
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
There have been some recent bugs that were triggered only when
preemptible RCU's __rcu_read_unlock() was preempted just after setting
->rcu_read_lock_nesting to INT_MIN, which is a low-probability event.
Therefore, reproducing those bugs (to say nothing of gaining confidence
in alleged fixes) was quite difficult. This commit therefore creates
a new debug-only RCU kernel config option that forces a short delay
in __rcu_read_unlock() to increase the probability of those sorts of
bugs occurring.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
When you do something like "t = kthread_run(...)", it is possible that
the kthread will start running before the assignment to "t" happens.
If the child kthread expects to find a pointer to its task_struct in "t",
it will then be fatally disappointed. This commit therefore switches
such cases to kthread_create() followed by wake_up_process(), guaranteeing
that the assignment happens before the child kthread starts running.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Drop a few characters by switching kernel/rcutorture.c from
"printk(KERN_ALERT" to "pr_alert(".
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Many rcutorture runs include CPU-hotplug operations in their stress
testing. This commit accumulates statistics on the durations of these
operations in deference to the recent concern about the overhead and
latency of these operations.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
A number of new features have been added to rcutorture over the years, but
the defaults have not been updated to include them. This commit therefore
turns on a couple of them that have proven helpful and trustworthy, namely
periodic progress reports and testing of NO_HZ.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Currently, rcu_init_geometry() only reshapes RCU's combining trees
if the leaf fanout is changed at boot time. This means that by
default, kernels compiled with (say) NR_CPUS=4096 will keep oversized
data structures, even when running on systems with (say) four CPUs.
This commit therefore checks to see if the maximum number of CPUs on
the actual running system (nr_cpu_ids) differs from NR_CPUS, and if so
reshapes the combining trees accordingly.
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
If CONFIG_RCU_FANOUT_EXACT=y, if there are not enough CPUs (according
to nr_cpu_ids) to require more than a single rcu_node structure, but if
NR_CPUS is larger than would fit into a single rcu_node structure, then
the current rcu_init_levelspread() code is subject to integer overflow
in the eight-bit ->levelspread[] array in the rcu_state structure.
In this case, the solution is -not- to increase the size of the
elements in this array because the values in that array should be
constrained to the number of bits in an unsigned long. Instead, this
commit replaces NR_CPUS with nr_cpu_ids in the rcu_init_levelspread()
function's initialization of the cprv local variable. This results in
all of the arithmetic being consistently based off of the nr_cpu_ids
value, thus avoiding the overflow, which was caused by the mixing of
nr_cpu_ids and NR_CPUS.
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The current quiescent-state detection algorithm is needlessly
complex. It records the grace-period number corresponding to
the quiescent state at the time of the quiescent state, which
works, but it seems better to simply erase any record of previous
quiescent states at the time that the CPU notices the new grace
period. This has the further advantage of removing another piece
of RCU for which lockless reasoning is required.
Therefore, this commit makes this change.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The synchronize_rcu_expedited() function disables interrupts across a
scan of all leaf rcu_node structures, which is not good for real-time
scheduling latency on large systems (hundreds or especially thousands
of CPUs). This commit therefore holds off CPU-hotplug operations using
get_online_cpus(), and removes the prior acquisiion of the ->onofflock
(which required disabling interrupts).
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
In the C language, signed overflow is undefined. It is true that
twos-complement arithmetic normally comes to the rescue, but if the
compiler can subvert this any time it has any information about the values
being compared. For example, given "if (a - b > 0)", if the compiler
has enough information to realize that (for example) the value of "a"
is positive and that of "b" is negative, the compiler is within its
rights to optimize to a simple "if (1)", which might not be what you want.
This commit therefore converts synchronize_rcu_expedited()'s work-done
detection counter from signed to unsigned.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Now that the rcu_node structures' ->completed fields are unconditionally
assigned at grace-period cleanup time, they should already have the
correct value for the new grace period at grace-period initialization
time. This commit therefore inserts a WARN_ON_ONCE() to verify this
invariant.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Preemption greatly raised the probability of certain types of race
conditions, so this commit adds an anti-heisenbug to greatly increase
the collision cross section, also known as the probability of occurrence.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The current approach to grace-period initialization is vulnerable to
extremely low-probability races. These races stem from the fact that
the old grace period is marked completed on the same traversal through
the rcu_node structure that is marking the start of the new grace period.
This means that some rcu_node structures will believe that the old grace
period is still in effect at the same time that other rcu_node structures
believe that the new grace period has already started.
These sorts of disagreements can result in too-short grace periods,
as shown in the following scenario:
1. CPU 0 completes a grace period, but needs an additional
grace period, so starts initializing one, initializing all
the non-leaf rcu_node structures and the first leaf rcu_node
structure. Because CPU 0 is both completing the old grace
period and starting a new one, it marks the completion of
the old grace period and the start of the new grace period
in a single traversal of the rcu_node structures.
Therefore, CPUs corresponding to the first rcu_node structure
can become aware that the prior grace period has completed, but
CPUs corresponding to the other rcu_node structures will see
this same prior grace period as still being in progress.
2. CPU 1 passes through a quiescent state, and therefore informs
the RCU core. Because its leaf rcu_node structure has already
been initialized, this CPU's quiescent state is applied to the
new (and only partially initialized) grace period.
3. CPU 1 enters an RCU read-side critical section and acquires
a reference to data item A. Note that this CPU believes that
its critical section started after the beginning of the new
grace period, and therefore will not block this new grace period.
4. CPU 16 exits dyntick-idle mode. Because it was in dyntick-idle
mode, other CPUs informed the RCU core of its extended quiescent
state for the past several grace periods. This means that CPU 16
is not yet aware that these past grace periods have ended. Assume
that CPU 16 corresponds to the second leaf rcu_node structure --
which has not yet been made aware of the new grace period.
5. CPU 16 removes data item A from its enclosing data structure
and passes it to call_rcu(), which queues a callback in the
RCU_NEXT_TAIL segment of the callback queue.
6. CPU 16 enters the RCU core, possibly because it has taken a
scheduling-clock interrupt, or alternatively because it has
more than 10,000 callbacks queued. It notes that the second
most recent grace period has completed (recall that because it
corresponds to the second as-yet-uninitialized rcu_node structure,
it cannot yet become aware that the most recent grace period has
completed), and therefore advances its callbacks. The callback
for data item A is therefore in the RCU_NEXT_READY_TAIL segment
of the callback queue.
7. CPU 0 completes initialization of the remaining leaf rcu_node
structures for the new grace period, including the structure
corresponding to CPU 16.
8. CPU 16 again enters the RCU core, again, possibly because it has
taken a scheduling-clock interrupt, or alternatively because
it now has more than 10,000 callbacks queued. It notes that
the most recent grace period has ended, and therefore advances
its callbacks. The callback for data item A is therefore in
the RCU_DONE_TAIL segment of the callback queue.
9. All CPUs other than CPU 1 pass through quiescent states. Because
CPU 1 already passed through its quiescent state, the new grace
period completes. Note that CPU 1 is still in its RCU read-side
critical section, still referencing data item A.
10. Suppose that CPU 2 wais the last CPU to pass through a quiescent
state for the new grace period, and suppose further that CPU 2
did not have any callbacks queued, therefore not needing an
additional grace period. CPU 2 therefore traverses all of the
rcu_node structures, marking the new grace period as completed,
but does not initialize a new grace period.
11. CPU 16 yet again enters the RCU core, yet again possibly because
it has taken a scheduling-clock interrupt, or alternatively
because it now has more than 10,000 callbacks queued. It notes
that the new grace period has ended, and therefore advances
its callbacks. The callback for data item A is therefore in
the RCU_DONE_TAIL segment of the callback queue. This means
that this callback is now considered ready to be invoked.
12. CPU 16 invokes the callback, freeing data item A while CPU 1
is still referencing it.
This scenario represents a day-zero bug for TREE_RCU. This commit
therefore ensures that the old grace period is marked completed in
all leaf rcu_node structures before a new grace period is marked
started in any of them.
That said, it would have been insanely difficult to force this race to
happen before the grace-period initialization process was preemptible.
Therefore, this commit is not a candidate for -stable.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Conflicts:
kernel/rcutree.c
The module parameters blimit, qhimark, and qlomark (and more
recently, rcu_fanout_leaf) have permission masks of zero, so
that their values are not visible from sysfs. This is unnecessary
and inconvenient to administrators who might like an easy way to
see what these values are on a running system. This commit therefore
sets their permission masks to 0444, allowing them to be read but
not written.
Reported-by: Rusty Russell <rusty@ozlabs.org>
Reported-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Although almost everyone is well-served by the defaults, some uses of RCU
benefit from shorter grace periods, while others benefit more from the
greater efficiency provided by longer grace periods. Situations requiring
a large number of grace periods to elapse (and wireshark startup has
been called out as an example of this) are helped by lower-latency
grace periods. Furthermore, in some embedded applications, people are
willing to accept a small degradation in update efficiency (due to there
being more of the shorter grace-period operations) in order to gain the
lower latency.
In contrast, those few systems with thousands of CPUs need longer grace
periods because the CPU overhead of a grace period rises roughly
linearly with the number of CPUs. Such systems normally do not make
much use of facilities that require large numbers of grace periods to
elapse, so this is a good tradeoff.
Therefore, this commit allows the durations to be controlled from sysfs.
There are two sysfs parameters, one named "jiffies_till_first_fqs" that
specifies the delay in jiffies from the end of grace-period initialization
until the first attempt to force quiescent states, and the other named
"jiffies_till_next_fqs" that specifies the delay (again in jiffies)
between subsequent attempts to force quiescent states. They both default
to three jiffies, which is compatible with the old hard-coded behavior.
At some future time, it may be possible to automatically increase the
grace-period length with the number of CPUs, but we do not yet have
sufficient data to do a good job. Preliminary data indicates that we
should add an addiitonal jiffy to each of the delays for every 200 CPUs
in the system, but more experimentation is needed. For now, the number
of systems with more than 1,000 CPUs is small enough that this can be
relegated to boot-time hand tuning.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Large systems running RCU_FAST_NO_HZ kernels see extreme memory
contention on the rcu_state structure's ->fqslock field. This
can be avoided by disabling RCU_FAST_NO_HZ, either at compile time
or at boot time (via the nohz kernel boot parameter), but large
systems will no doubt become sensitive to energy consumption.
This commit therefore uses a combining-tree approach to spread the
memory contention across new cache lines in the leaf rcu_node structures.
This can be thought of as a tournament lock that has only a try-lock
acquisition primitive.
The effect on small systems is minimal, because such systems have
an rcu_node "tree" consisting of a single node. In addition, this
functionality is not used on fastpaths.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Moving quiescent-state forcing into a kthread dispenses with the need
for the ->n_rp_need_fqs field, so this commit removes it.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
RCU quiescent-state forcing is currently carried out without preemption
points, which can result in excessive latency spikes on large systems
(many hundreds or thousands of CPUs). This patch therefore inserts
a voluntary preemption point into force_qs_rnp(), which should greatly
reduce the magnitude of these spikes.
Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
As the first step towards allowing quiescent-state forcing to be
preemptible, this commit moves RCU quiescent-state forcing into the
same kthread that is now used to initialize and clean up after grace
periods. This is yet another step towards keeping scheduling
latency down to a dull roar.
Updated to change from raw_spin_lock_irqsave() to raw_spin_lock_irq()
and to remove the now-unused rcu_state structure fields as suggested by
Peter Zijlstra.
Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The fields in the rcu_state structure that are protected by the
root rcu_node structure's ->lock can share a cache line with the
fields protected by ->onofflock. This can result in excessive
memory contention on large systems, so this commit applies
____cacheline_internodealigned_in_smp to the ->onofflock field in
order to segregate them.
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
In kernels built with CONFIG_RCU_FAST_NO_HZ=y, CPUs can accumulate a
large number of lazy callbacks, which as the name implies will be slow
to be invoked. This can be a problem on small-memory systems, where the
default 6-second sleep for CPUs having only lazy RCU callbacks could well
be fatal. This commit therefore installs an OOM hander that ensures that
every CPU with lazy callbacks has at least one non-lazy callback, in turn
ensuring timely advancement for these callbacks.
Updated to fix bug that disabled OOM killing, noted by Lai Jiangshan.
Updated to push the for_each_rcu_flavor() loop into rcu_oom_notify_cpu(),
thus reducing the number of IPIs, as suggested by Steven Rostedt. Also
to make the for_each_online_cpu() loop be preemptible. (Later, it might
be good to use smp_call_function(), as suggested by Peter Zijlstra.)
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Earlier versions of RCU invoked the RCU core from the CPU_DYING notifier
in order to note a quiescent state for the outgoing CPU. Because the
CPU is marked "offline" during the execution of the CPU_DYING notifiers,
the RCU core had to tolerate being invoked from an offline CPU. However,
commit b1420f1c (Make rcu_barrier() less disruptive) left only tracing
code in the CPU_DYING notifier, so the RCU core need no longer execute
on offline CPUs. This commit therefore enforces this restriction.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Then rcu_gp_kthread() function is too large and furthermore needs to
have the force_quiescent_state() code pulled in. This commit therefore
breaks up rcu_gp_kthread() into rcu_gp_init() and rcu_gp_cleanup().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
RCU grace-period cleanup is currently carried out with interrupts
disabled, which can result in excessive latency spikes on large systems
(many hundreds or thousands of CPUs). This patch therefore makes the
RCU grace-period cleanup be preemptible, including voluntary preemption
points, which should eliminate those latency spikes. Similar spikes from
forcing of quiescent states will be dealt with similarly by later patches.
Updated to replace uses of spin_lock_irqsave() with spin_lock_irq(), as
suggested by Peter Zijlstra.
Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
As a first step towards allowing grace-period cleanup to be preemptible,
this commit moves the RCU grace-period cleanup into the same kthread
that is now used to initialize grace periods. This is needed to keep
scheduling latency down to a dull roar.
[ paulmck: Get rid of stray spin_lock_irqsave() calls. ]
Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
RCU grace-period initialization is currently carried out with interrupts
disabled, which can result in 200-microsecond latency spikes on systems
on which RCU has been configured for 4096 CPUs. This patch therefore
makes the RCU grace-period initialization be preemptible, which should
eliminate those latency spikes. Similar spikes from grace-period cleanup
and the forcing of quiescent states will be dealt with similarly by later
patches.
Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The next step in reducing RCU's grace-period initialization latency on
large systems will make this initialization preemptible. Unfortunately,
making the grace-period initialization subject to interrupts (let alone
preemption) exposes the following race on systems whose rcu_node tree
contains more than one node:
1. CPU 31 starts initializing the grace period, including the
first leaf rcu_node structures, and is then preempted.
2. CPU 0 refers to the first leaf rcu_node structure, and notes
that a new grace period has started. It passes through a
quiescent state shortly thereafter, and informs the RCU core
of this rite of passage.
3. CPU 0 enters an RCU read-side critical section, acquiring
a pointer to an RCU-protected data item.
4. CPU 31 takes an interrupt whose handler removes the data item
referenced by CPU 0 from the data structure, and registers an
RCU callback in order to free it.
5. CPU 31 resumes initializing the grace period, including its
own rcu_node structure. In invokes rcu_start_gp_per_cpu(),
which advances all callbacks, including the one registered
in #4 above, to be handled by the current grace period.
6. The remaining CPUs pass through quiescent states and inform
the RCU core, but CPU 0 remains in its RCU read-side critical
section, still referencing the now-removed data item.
7. The grace period completes and all the callbacks are invoked,
including the one that frees the data item that CPU 0 is still
referencing. Oops!!!
One way to avoid this race is to remove grace-period acceleration from
rcu_start_gp_per_cpu(). Now, the only reason for this acceleration was
to allow CPUs bringing RCU out of idle state to have their callbacks
invoked after only one grace period, rather than the two grace periods
that would otherwise be required. But this acceleration does not
work when RCU grace-period initialization is moved to a kthread because
the CPU posting the callback is no longer necessarily the CPU that is
initializing the resulting grace period.
This commit therefore removes this now-pointless (and soon to be dangerous)
grace-period acceleration, thus avoiding the above race.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
As the first step towards allowing grace-period initialization to be
preemptible, this commit moves the RCU grace-period initialization
into its own kthread. This is needed to keep large-system scheduling
latency at reasonable levels.
Also change raw_spin_lock_irqsave() to raw_spin_lock_irq() as suggested
by Peter Zijlstra in review comments.
Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Each grace period is supposed to have at least one callback waiting
for that grace period to complete. However, if CONFIG_NO_HZ=n, an
extra callback-free grace period is no big problem -- it will chew up
a tiny bit of CPU time, but it will complete normally. In contrast,
CONFIG_NO_HZ=y kernels have the potential for all the CPUs to go to
sleep indefinitely, in turn indefinitely delaying completion of the
callback-free grace period. Given that nothing is waiting on this grace
period, this is also not a problem.
That is, unless RCU CPU stall warnings are also enabled, as they are
in recent kernels. In this case, if a CPU wakes up after at least one
minute of inactivity, an RCU CPU stall warning will result. The reason
that no one noticed until quite recently is that most systems have enough
OS noise that they will never remain absolutely idle for a full minute.
But there are some embedded systems with cut-down userspace configurations
that consistently get into this situation.
All this begs the question of exactly how a callback-free grace period
gets started in the first place. This can happen due to the fact that
CPUs do not necessarily agree on which grace period is in progress.
If a CPU still believes that the grace period that just completed is
still ongoing, it will believe that it has callbacks that need to wait for
another grace period, never mind the fact that the grace period that they
were waiting for just completed. This CPU can therefore erroneously
decide to start a new grace period. Note that this can happen in
TREE_RCU and TREE_PREEMPT_RCU even on a single-CPU system: Deadlock
considerations mean that the CPU that detected the end of the grace
period is not necessarily officially informed of this fact for some time.
Once this CPU notices that the earlier grace period completed, it will
invoke its callbacks. It then won't have any callbacks left. If no
other CPU has any callbacks, we now have a callback-free grace period.
This commit therefore makes CPUs check more carefully before starting a
new grace period. This new check relies on an array of tail pointers
into each CPU's list of callbacks. If the CPU is up to date on which
grace periods have completed, it checks to see if any callbacks follow
the RCU_DONE_TAIL segment, otherwise it checks to see if any callbacks
follow the RCU_WAIT_TAIL segment. The reason that this works is that
the RCU_WAIT_TAIL segment will be promoted to the RCU_DONE_TAIL segment
as soon as the CPU is officially notified that the old grace period
has ended.
This change is to cpu_needs_another_gp(), which is called in a number
of places. The only one that really matters is in rcu_start_gp(), where
the root rcu_node structure's ->lock is held, which prevents any
other CPU from starting or completing a grace period, so that the
comparison that determines whether the CPU is missing the completion
of a grace period is stable.
Reported-by: Becky Bruce <bgillbruce@gmail.com>
Reported-by: Subodh Nijsure <snijsure@grid-net.com>
Reported-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Paul Walmsley <paul@pwsan.com> # OMAP3730, OMAP4430
Cc: stable@vger.kernel.org
Pull timer fix from Ingo Molnar:
"One more timekeeping fix for v3.6"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time: Fix timeekeping_get_ns overflow on 32bit systems
e0aecdd874 ("workqueue: use irqsafe timer for delayed_work") made
try_to_grab_pending() safe to use from irq context but forgot to
remove WARN_ON_ONCE(in_irq()). Remove it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Pull workqueue / powernow-k8 fix from Tejun Heo:
"This is the fix for the bug where cpufreq/powernow-k8 was tripping
BUG_ON() in try_to_wake_up_local() by migrating workqueue worker to a
different CPU.
https://bugzilla.kernel.org/show_bug.cgi?id=47301
As discussed, the fix is now two parts - one to reimplement
work_on_cpu() so that it doesn't create a new kthread each time and
the actual fix which makes powernow-k8 use work_on_cpu() instead of
performing manual migration.
While pretty late in the merge cycle, both changes are on the safer
side. Jiri and I verified two existing users of work_on_cpu() and
Duncan confirmed that the powernow-k8 fix survived about 18 hours of
testing."
* 'for-3.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
cpufreq/powernow-k8: workqueue user shouldn't migrate the kworker to another CPU
workqueue: reimplement work_on_cpu() using system_wq
workqueue_set_max_active() may increase ->max_active without
activating delayed works and may make the activation order differ from
the queueing order. Both aren't strictly bugs but the resulting
behavior could be a bit odd.
To make things more consistent, use cwq_set_max_active() helper which
immediately makes use of the newly increased max_mactive if there are
delayed work items and also keeps the activation order.
tj: Slight update to description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Using a helper instead of open code makes thaw_workqueues() clearer.
The helper will also be used by the next patch.
tj: Slight update to comment and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The existing work_on_cpu() implementation is hugely inefficient. It
creates a new kthread, execute that single function and then let the
kthread die on each invocation.
Now that system_wq can handle concurrent executions, there's no
advantage of doing this. Reimplement work_on_cpu() using system_wq
which makes it simpler and way more efficient.
stable: While this isn't a fix in itself, it's needed to fix a
workqueue related bug in cpufreq/powernow-k8. AFAICS, this
shouldn't break other existing users.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: stable@vger.kernel.org
@delayed is now always false for all callers, remove it.
tj: Updated description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, when try_to_grab_pending() grabs a delayed work item, it
leaves its linked work items alone on the delayed_works. The linked
work items are always NO_COLOR and will cause future
cwq_activate_first_delayed() increase cwq->nr_active incorrectly, and
may cause the whole cwq to stall. For example,
state: cwq->max_active = 1, cwq->nr_active = 1
one work in cwq->pool, many in cwq->delayed_works.
step1: try_to_grab_pending() removes a work item from delayed_works
but leaves its NO_COLOR linked work items on it.
step2: Later on, cwq_activate_first_delayed() activates the linked
work item increasing ->nr_active.
step3: cwq->nr_active = 1, but all activated work items of the cwq are
NO_COLOR. When they finish, cwq->nr_active will not be
decreased due to NO_COLOR, and no further work items will be
activated from cwq->delayed_works. the cwq stalls.
Fix it by ensuring the target work item is activated before stealing
PENDING in try_to_grab_pending(). This ensures that all the linked
work items are activated without incorrectly bumping cwq->nr_active.
tj: Updated comment and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
workqueue_cpu_down_callback() is used only if HOTPLUG_CPU=y, so
hotcpu_notifier() fits better than cpu_notifier().
When HOTPLUG_CPU=y, hotcpu_notifier() and cpu_notifier() are the same.
When HOTPLUG_CPU=n, if we use cpu_notifier(),
workqueue_cpu_down_callback() will be called during boot to do
nothing, and the memory of workqueue_cpu_down_callback() and
gcwq_unbind_fn() will be discarded after boot.
If we use hotcpu_notifier(), we can avoid the no-op call of
workqueue_cpu_down_callback() and the memory of
workqueue_cpu_down_callback() and gcwq_unbind_fn() will be discard at
build time:
$ ls -l kernel/workqueue.o.cpu_notifier kernel/workqueue.o.hotcpu_notifier
-rw-rw-r-- 1 laijs laijs 484080 Sep 15 11:31 kernel/workqueue.o.cpu_notifier
-rw-rw-r-- 1 laijs laijs 478240 Sep 15 11:31 kernel/workqueue.o.hotcpu_notifier
$ size kernel/workqueue.o.cpu_notifier kernel/workqueue.o.hotcpu_notifier
text data bss dec hex filename
18513 2387 1221 22121 5669 kernel/workqueue.o.cpu_notifier
18082 2355 1221 21658 549a kernel/workqueue.o.hotcpu_notifier
tj: Updated description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
For workqueue hotplug callbacks, it makes less sense to use __devinit
which discards the memory after boot if !HOTPLUG. __cpuinit, which
discards the memory after boot if !HOTPLUG_CPU fits better.
tj: Updated description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that manager_mutex's role has changed from synchronizing manager
role to excluding hotplug against manager, the name is misleading.
As it is protecting the CPU-association of the gcwq now, rename it to
assoc_mutex.
This patch is pure rename and doesn't introduce any functional change.
tj: Updated comments and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Now both worker destruction and idle rebinding remove the worker from
idle list while it's still idle, so list_empty(&worker->entry) can be
used to test whether either is pending and WORKER_DIE to distinguish
between the two instead making WORKER_REBIND unnecessary.
Use list_empty(&worker->entry) to determine whether destruction or
rebinding is pending. This simplifies worker state transitions.
WORKER_REBIND is not needed anymore. Remove it.
tj: Updated comments and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Because the old unbind/rebinding implementation wasn't atomic w.r.t.
GCWQ_DISASSOCIATED manipulation which is protected by
global_cwq->lock, we had to use two flags, WORKER_UNBOUND and
WORKER_REBIND, to avoid incorrectly losing all NOT_RUNNING bits with
back-to-back CPU hotplug operations; otherwise, completion of
rebinding while another unbinding is in progress could clear UNBIND
prematurely.
Now that both unbind/rebinding are atomic w.r.t. GCWQ_DISASSOCIATED,
there's no need to use two flags. Just one is enough. Don't use
WORKER_REBIND for busy rebinding.
tj: Updated description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently rebind_workers() uses rebinds idle workers synchronously
before proceeding to requesting busy workers to rebind. This is
necessary because all workers on @worker_pool->idle_list must be bound
before concurrency management local wake-ups from the busy workers
take place.
Unfortunately, the synchronous idle rebinding is quite complicated.
This patch reimplements idle rebinding to simplify the code path.
Rather than trying to make all idle workers bound before rebinding
busy workers, we simply remove all to-be-bound idle workers from the
idle list and let them add themselves back after completing rebinding
(successful or not).
As only workers which finished rebinding can on on the idle worker
list, the idle worker list is guaranteed to have only bound workers
unless CPU went down again and local wake-ups are safe.
After the change, @worker_pool->nr_idle may deviate than the actual
number of idle workers on @worker_pool->idle_list. More specifically,
nr_idle may be non-zero while ->idle_list is empty. All users of
->nr_idle and ->idle_list are audited. The only affected one is
too_many_workers() which is updated to check %false if ->idle_list is
empty regardless of ->nr_idle.
After this patch, rebind_workers() no longer performs the nasty
idle-rebind retries which require temporary release of gcwq->lock, and
both unbinding and rebinding are atomic w.r.t. global_cwq->lock.
worker->idle_rebind and global_cwq->rebind_hold are now unnecessary
and removed along with the definition of struct idle_rebind.
Changed from V1:
1) remove unlikely from too_many_workers(), ->idle_list can be empty
anytime, even before this patch, no reason to use unlikely.
2) fix a small rebasing mistake.
(which is from rebasing the orignal fixing patch to for-next)
3) add a lot of comments.
4) clear WORKER_REBIND unconditionaly in idle_worker_rebind()
tj: Updated comments and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Implement kprojid_t a cousin of the kuid_t and kgid_t.
The per user namespace mapping of project id values can be set with
/proc/<pid>/projid_map.
A full compliment of helpers is provided: make_kprojid, from_kprojid,
from_kprojid_munged, kporjid_has_mapping, projid_valid, projid_eq,
projid_eq, projid_lt.
Project identifiers are part of the generic disk quota interface,
although it appears only xfs implements project identifiers currently.
The xfs code allows anyone who has permission to set the project
identifier on a file to use any project identifier so when
setting up the user namespace project identifier mappings I do
not require a capability.
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
- When tracing capture the kuid.
- When displaying the data to user space convert the kuid into the
user namespace of the process that opened the report file.
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
BSD process accounting conveniently passes the file the accounting
records will be written into to do_acct_process. The file credentials
captured the user namespace of the opener of the file. Use the file
credentials to format the uid and the gid of the current process into
the user namespace of the user that started the bsd process
accounting.
Cc: Pavel Emelyanov <xemul@openvz.org>
Reviewed-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
- Explicitly limit exit task stat broadcast to the initial user and
pid namespaces, as it is already limited to the initial network
namespace.
- For broadcast task stats explicitly generate all of the idenitiers
in terms of the initial user namespace and the initial pid
namespace.
- For request stats report them in terms of the current user namespace
and the current pid namespace. Netlink messages are delivered
syncrhonously to the kernel allowing us to get the user namespace
and the pid namespace from the current task.
- Pass the namespaces for representing pids and uids and gids
into bacct_add_task.
Cc: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
- Explicitly format uids gids in audit messges in the initial user
namespace. This is safe because auditd is restrected to be in
the initial user namespace.
- Convert audit_sig_uid into a kuid_t.
- Enable building the audit code and user namespaces at the same time.
The net result is that the audit subsystem now uses kuid_t and kgid_t whenever
possible making it almost impossible to confuse a raw uid_t with a kuid_t
preventing bugs.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Always store audit loginuids in type kuid_t.
Print loginuids by converting them into uids in the appropriate user
namespace, and then printing the resulting uid.
Modify audit_get_loginuid to return a kuid_t.
Modify audit_set_loginuid to take a kuid_t.
Modify /proc/<pid>/loginuid on read to convert the loginuid into the
user namespace of the opener of the file.
Modify /proc/<pid>/loginud on write to convert the loginuid
rom the user namespace of the opener of the file.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Paul Moore <paul@paul-moore.com> ?
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
The audit filter code guarantees that uid are always compared with
uids and gids are always compared with gids, as the comparason
operations are type specific. Take advantage of this proper to define
audit_uid_comparator and audit_gid_comparator which use the type safe
comparasons from uidgid.h.
Build on audit_uid_comparator and audit_gid_comparator and replace
audit_compare_id with audit_compare_uid and audit_compare_gid. This
is one of those odd cases where being type safe and duplicating code
leads to simpler shorter and more concise code.
Don't allow bitmask operations in uid and gid comparisons in
audit_data_to_entry. Bitmask operations are already denined in
audit_rule_to_entry.
Convert constants in audit_rule_to_entry and audit_data_to_entry into
kuids and kgids when appropriate.
Convert the uid and gid field in struct audit_names to be of type
kuid_t and kgid_t respectively, so that the new uid and gid comparators
can be applied in a type safe manner.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
The only place we use the uid and the pid that we calculate in
audit_receive_msg is in audit_log_common_recv_msg so move the
calculation of these values into the audit_log_common_recv_msg.
Simplify the calcuation of the current pid and uid by
reading them from current instead of reading them from
NETLINK_CREDS.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
For user generated audit messages set the portid field in the netlink
header to the netlink port where the user generated audit message came
from. Reporting the process id in a port id field was just nonsense.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Use current instead of looking up the current up the current task by
process identifier. Netlink requests are processed in trhe context of
the sending task so this is safe.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Now that netlink messages are processed in the context of the sender
tty_audit_push_task can be called directly and audit_prepare_user_tty
which only added looking up the task of the tty by process id is
not needed.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Get caller process uid and gid and pid values from the current task
instead of the NETLINK_CB. This is simpler than passing NETLINK_CREDS
from from audit_receive_msg to audit_filter_user_rules and avoid the
chance of being hit by the occassional bugs in netlink uid/gid
credential passing. This is a safe changes because all netlink
requests are processed in the task of the sending process.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This allows the code to safely make the assumption that all of the
uids gids and pids that need to be send in audit messages are in the
initial namespaces.
If someone cares we may lift this restriction someday but start with
limiting access so at least the code is always correct.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This merge is necessary as Lai's CPU hotplug restructuring series
depends on the CPU hotplug bug fixes in for-3.6-fixes.
The merge creates one trivial conflict between the following two
commits.
96e65306b8 "workqueue: UNBOUND -> REBIND morphing in rebind_workers() should be atomic"
e2b6a6d570 "workqueue: use system_highpri_wq for highpri workers in rebind_workers()"
Both add local variable definitions to the same block and can be
merged in any order.
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull another workqueue fix from Tejun Heo:
"Unfortunately, yet another late fix. This too is discovered and fixed
by Lai. This bug was introduced during this merge window by commit
25511a4776 ("workqueue: reimplement CPU online rebinding to handle
idle workers") which started using WORKER_REBIND flag for idle rebind
too.
The bug is relatively easy to trigger if the CPU rapidly goes through
off, on and then off (and stay off). The fix is on the safer side.
This hasn't been on linux-next yet but I'm pushing early so that it
can get more exposure before v3.6 release."
* 'for-3.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: always clear WORKER_REBIND in busy_worker_rebind_fn()
The kernel doesn't check the pid for negative values, so if you try to
write -2 to /proc/sys/kernel/ns_last_pid, you will get a kernel panic.
The crash happens because the next pid is -1, and alloc_pidmap() will
try to access to a nonexistent pidmap.
map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* pm-sleep:
properly __init-annotate pm_sysrq_init()
PM / wakeup: Use irqsave/irqrestore for events_lock
PM / Freezer: Fix small typo "regrigerator"
PM / Sleep: Print name of wakeup source that aborts suspend
Linus Torvalds
Al Viro
Oleg Nesterov
David S. Miller
Masami Hiramatsu
Rusty Russell
David Howells
Matthew Garrett
James Morris
Anton Vorontsov
Paul E. McKenney
Frederic Weisbecker
Paul E. McKenney
Eric Dumazet
Ezequiel Garcia
Mandeep Singh Baines
John Stultz
Todd Poynor
Peter Zijlstra
Li Zhong
Dimitri Sivanich
Tejun Heo
Lai Jiangshan
Ingo Molnar
Eric W. Biederman
Andrew Vagin
Rafael J. Wysocki