Jiri Olsa 06f417968b perf: Remove WARN_ON_ONCE() check in __perf_event_enable() for valid scenario ...

The '!ctx->is_active' check has a valid scenario, so
there's no need for the warning.

The reason is that there's a time window between the
'ctx->is_active' check in the perf_event_enable() function
and the __perf_event_enable() function having:

  - IRQs on
  - ctx->lock unlocked

where the task could be killed and 'ctx' deactivated by
perf_event_exit_task(), ending up with the warning below.

So remove the WARN_ON_ONCE() check and add comments to
explain it all.

This addresses the following warning reported by Vince Weaver:

[  324.983534] ------------[ cut here ]------------
[  324.984420] WARNING: at kernel/events/core.c:1953 __perf_event_enable+0x187/0x190()
[  324.984420] Modules linked in:
[  324.984420] CPU: 19 PID: 2715 Comm: nmi_bug_snb Not tainted 3.10.0+ #246
[  324.984420] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010
[  324.984420]  0000000000000009 ffff88043fce3ec8 ffffffff8160ea0b ffff88043fce3f00
[  324.984420]  ffffffff81080ff0 ffff8802314fdc00 ffff880231a8f800 ffff88043fcf7860
[  324.984420]  0000000000000286 ffff880231a8f800 ffff88043fce3f10 ffffffff8108103a
[  324.984420] Call Trace:
[  324.984420]  <IRQ>  [<ffffffff8160ea0b>] dump_stack+0x19/0x1b
[  324.984420]  [<ffffffff81080ff0>] warn_slowpath_common+0x70/0xa0
[  324.984420]  [<ffffffff8108103a>] warn_slowpath_null+0x1a/0x20
[  324.984420]  [<ffffffff81134437>] __perf_event_enable+0x187/0x190
[  324.984420]  [<ffffffff81130030>] remote_function+0x40/0x50
[  324.984420]  [<ffffffff810e51de>] generic_smp_call_function_single_interrupt+0xbe/0x130
[  324.984420]  [<ffffffff81066a47>] smp_call_function_single_interrupt+0x27/0x40
[  324.984420]  [<ffffffff8161fd2f>] call_function_single_interrupt+0x6f/0x80
[  324.984420]  <EOI>  [<ffffffff816161a1>] ? _raw_spin_unlock_irqrestore+0x41/0x70
[  324.984420]  [<ffffffff8113799d>] perf_event_exit_task+0x14d/0x210
[  324.984420]  [<ffffffff810acd04>] ? switch_task_namespaces+0x24/0x60
[  324.984420]  [<ffffffff81086946>] do_exit+0x2b6/0xa40
[  324.984420]  [<ffffffff8161615c>] ? _raw_spin_unlock_irq+0x2c/0x30
[  324.984420]  [<ffffffff81087279>] do_group_exit+0x49/0xc0
[  324.984420]  [<ffffffff81096854>] get_signal_to_deliver+0x254/0x620
[  324.984420]  [<ffffffff81043057>] do_signal+0x57/0x5a0
[  324.984420]  [<ffffffff8161a164>] ? __do_page_fault+0x2a4/0x4e0
[  324.984420]  [<ffffffff8161665c>] ? retint_restore_args+0xe/0xe
[  324.984420]  [<ffffffff816166cd>] ? retint_signal+0x11/0x84
[  324.984420]  [<ffffffff81043605>] do_notify_resume+0x65/0x80
[  324.984420]  [<ffffffff81616702>] retint_signal+0x46/0x84
[  324.984420] ---[ end trace 442ec2f04db3771a ]---

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1373384651-6109-2-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2013-07-12 11:11:01 +02:00

..

cpu

idle: Enable interrupts in the weak arch_cpu_idle() implementation

2013-06-14 23:01:05 +02:00

debug

kgdb/sysrq: fix inconstistent help message of sysrq key

2013-04-30 17:04:10 -07:00

events

perf: Remove WARN_ON_ONCE() check in __perf_event_enable() for valid scenario

2013-07-12 11:11:01 +02:00

gcov

kernel/gcov: remove depends on CONFIG_EXPERIMENTAL

2013-01-11 11:39:33 -08:00

irq

Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-07-02 16:14:35 -07:00

power

Finally eradicate CONFIG_HOTPLUG

2013-06-03 14:20:18 -07:00

sched

Merge tag 'v3.10' into sched/core

2013-07-01 11:18:53 +02:00

time

tick: Fix tick_broadcast_pending_mask not cleared

2013-06-21 13:10:34 +02:00

trace

tracing: Fix outputting formats of x86-tsc and counter when use trace_clock

2013-06-11 13:58:46 -04:00

.gitignore

kernel/hz.bc: ignore.

2013-04-22 07:09:06 -07:00

acct.c

fs: Fix hang with BSD accounting on frozen filesystem

2013-05-04 14:57:58 -04:00

async.c

async: rename and redefine async_func_ptr

2013-03-12 13:59:14 -07:00

audit_tree.c

kernel/audit_tree.c:audit_add_tree_rule(): protect `rule' from kill_rules()

2013-06-12 16:29:46 -07:00

audit_watch.c

audit: catch possible NULL audit buffers

2013-01-11 14:54:55 -08:00

audit.c

audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE

2013-06-12 16:29:45 -07:00

audit.h

Merge git://git.infradead.org/users/eparis/audit

2013-05-11 14:29:11 -07:00

auditfilter.c

auditfilter.c: fix kernel-doc warnings

2013-05-24 16:22:52 -07:00

auditsc.c

audit: Make testing for a valid loginuid explicit.

2013-05-07 22:27:15 -04:00

backtracetest.c

…

bounds.c

…

capability.c

Add file_ns_capable() helper function for open-time capability checking

2013-04-14 10:06:31 -07:00

cgroup_freezer.c

cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free()

2012-11-19 08:13:38 -08:00

cgroup.c

cgroup: warn about mismatching options of a new mount of an existing hierarchy

2013-05-29 07:59:39 +09:00

compat.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

2013-05-01 07:21:43 -07:00

configs.c

proc: Supply PDE attribute setting accessor functions

2013-05-01 17:29:18 -04:00

context_tracking.c

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-06-20 08:18:35 -10:00

cpu_pm.c

kernel/cpu_pm.c: fix various typos

2012-05-31 17:49:27 -07:00

cpu.c

CPU hotplug: provide a generic helper to disable/enable CPU hotplug

2013-06-12 16:29:44 -07:00

cpuset.c

sched: Rename sched.c as sched/core.c in comments and Documentation

2013-06-19 12:58:42 +02:00

crash_dump.c

…

cred.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2012-12-18 10:55:28 -08:00

delayacct.c

cputime: Use accessors to read task cputime stats

2013-01-27 19:23:31 +01:00

dma.c

Remove all #inclusions of asm/system.h

2012-03-28 18:30:03 +01:00

elfcore.c

…

exec_domain.c

…

exit.c

move exit_task_namespaces() outside of exit_notify()

2013-06-15 05:39:08 +04:00

extable.c

extable: Flip the sorting message

2013-04-15 13:25:16 +02:00

fork.c

Merge branch 'for-3.10/drivers' of git://git.kernel.dk/linux-block

2013-05-08 11:51:05 -07:00

freezer.c

freezer: change ptrace_stop/do_signal_stop to use freezable_schedule()

2012-10-26 14:27:49 -07:00

futex_compat.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

2013-02-23 18:50:11 -08:00

futex.c

futex: Use freezable blocking call

2013-06-25 23:11:19 +02:00

groups.c

userns: Convert in_group_p and in_egroup_p to use kgid_t

2012-05-03 03:29:33 -07:00

hrtimer.c

Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-05-05 13:23:27 -07:00

hung_task.c

hung task debugging: Inject NMI when hung and going to panic

2012-04-25 12:39:25 +02:00

irq_work.c

Merge branch 'nohz/printk-v8' into irq/core

2013-02-05 00:48:46 +01:00

itimer.c

itimer: Use printk_once instead of WARN_ONCE

2012-04-10 11:00:30 +02:00

jump_label.c

jump_label: Export jump_label_rate_limit()

2012-08-06 19:00:35 +03:00

kallsyms.c

kernel: kallsyms: memory override issue, need check destination buffer length

2013-04-15 15:17:26 +09:30

kcmp.c

kcmp: include linux/ptrace.h

2012-12-20 17:40:19 -08:00

Kconfig.freezer

…

Kconfig.hz

…

Kconfig.locks

locking: Fix copy/paste errors of "ARCH_INLINE_*_UNLOCK_BH"

2013-05-28 08:50:00 +02:00

Kconfig.preempt

locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage

2012-03-23 13:18:57 +01:00

kexec.c

kexec: Use min() and min_t() to simplify logic

2013-04-30 17:04:07 -07:00

kmod.c

usermodehelper: check subprocess_info->path != NULL

2013-05-16 12:01:11 -07:00

kprobes.c

kprobes: Fix to free gone and unused optprobes

2013-05-28 10:37:59 +02:00

ksysfs.c

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-12-11 18:10:49 -08:00

kthread.c

kthread: implement probe_kthread_data()

2013-04-30 17:04:02 -07:00

latencytop.c

…

lglock.c

brlocks/lglocks: turn into functions

2012-05-29 23:28:41 -04:00

lockdep_internals.h

…

lockdep_proc.c

lockdep: Use KSYM_NAME_LEN'ed buffer for __get_key_name()

2012-10-24 12:39:09 +02:00

lockdep_states.h

…

lockdep.c

Merge branch 'for-3.10/drivers' of git://git.kernel.dk/linux-block

2013-05-08 11:51:05 -07:00

Makefile

Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

2013-05-05 10:58:06 -07:00

modsign_certificate.S

CONFIG_SYMBOL_PREFIX: cleanup.

2013-03-15 15:09:43 +10:30

modsign_pubkey.c

keys: use keyring_alloc() to create module signing keyring

2012-12-20 17:40:21 -08:00

module_signing.c

MODSIGN: Don't use enum-type bitfields in module signature info block

2012-12-05 11:27:24 +10:30

module-internal.h

MODSIGN: Move the magic string to the end of a module and eliminate the search

2012-10-19 17:30:40 -07:00

module.c

kmemleak: No need for scanning specific module sections

2013-05-17 09:53:36 +01:00

mutex-debug.c

…

mutex-debug.h

…

mutex.c

mutex: Add w/w mutex slowpath debugging

2013-06-26 12:10:56 +02:00

mutex.h

…

notifier.c

…

nsproxy.c

proc: Split the namespace stuff out into linux/proc_ns.h

2013-05-01 17:29:39 -04:00

padata.c

padata: use __this_cpu_read per-cpu helper

2012-12-06 17:16:23 +08:00

panic.c

dump_stack: implement arch-specific hardware description in task dumps

2013-04-30 17:04:02 -07:00

params.c

params: Fix potential memory leak in add_sysfs_param()

2013-03-18 11:40:21 +00:00

pid_namespace.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2013-05-01 17:51:54 -07:00

pid.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2013-05-01 17:51:54 -07:00

posix-cpu-timers.c

posix_timers: Fix pre-condition to stop the tick on full dynticks

2013-04-22 19:59:25 +02:00

posix-timers.c

posix-timers: Remove unused variable

2013-04-18 12:51:19 +02:00

printk.c

kmsg: honor dmesg_restrict sysctl on /dev/kmsg

2013-06-12 16:29:44 -07:00

profile.c

proc: Supply PDE attribute setting accessor functions

2013-05-01 17:29:18 -04:00

ptrace.c

Fix: kernel/ptrace.c: ptrace_peek_siginfo() missing __put_user() validation

2013-06-29 11:29:08 -07:00

range.c

range: Do not add new blank slot with add_range_with_merge

2013-06-18 11:32:10 -05:00

rcu.h

rcu: Provide RCU CPU stall warnings for tiny RCU

2013-01-28 22:06:21 -08:00

rcupdate.c

Merge branches 'cbnum.2013.06.10a', 'doc.2013.06.10a', 'fixes.2013.06.10a', 'srcu.2013.06.10a' and 'tiny.2013.06.10a' into HEAD

2013-06-10 13:46:44 -07:00

rcutiny_plugin.h

rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs

2013-06-10 13:45:53 -07:00

rcutiny.c

rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs

2013-06-10 13:45:53 -07:00

rcutorture.c

rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw().

2013-06-10 13:45:25 -07:00

rcutree_plugin.h

Merge branches 'cbnum.2013.06.10a', 'doc.2013.06.10a', 'fixes.2013.06.10a', 'srcu.2013.06.10a' and 'tiny.2013.06.10a' into HEAD

2013-06-10 13:46:44 -07:00

rcutree_trace.c

rcutrace: single_open() leaks

2013-05-05 00:16:35 -04:00

rcutree.c

Merge branches 'cbnum.2013.06.10a', 'doc.2013.06.10a', 'fixes.2013.06.10a', 'srcu.2013.06.10a' and 'tiny.2013.06.10a' into HEAD

2013-06-10 13:46:44 -07:00

rcutree.h

rcu: Drive quiescent-state-forcing delay from HZ

2013-06-10 13:44:56 -07:00

relay.c

Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-block

2013-05-08 10:13:35 -07:00

res_counter.c

res_counter: return amount of charges after res_counter_uncharge()

2012-12-18 15:02:12 -08:00

resource.c

ACPI/APEI: Add parameter check before error injection

2013-06-06 15:20:51 -07:00

rtmutex_common.h

…

rtmutex-debug.c

sched/rt: Move rt specific bits into new header file

2013-02-07 20:51:08 +01:00

rtmutex-debug.h

…

rtmutex-tester.c

locking/rtmutex/tester: Set correct permissions on sysfs files

2013-04-10 14:48:37 +02:00

rtmutex.c

rtmutex: Document rt_mutex_adjust_prio_chain()

2013-05-28 09:23:52 +02:00

rtmutex.h

…

rwsem.c

Revert "rw_semaphore: remove up/down_read_non_owner"

2013-03-23 15:53:52 -07:00

seccomp.c

seccomp: allow BPF_XOR based ALU instructions.

2013-03-26 11:07:19 +11:00

semaphore.c

semaphore: use `bool' type for semaphore_waiter's up

2013-04-30 17:04:08 -07:00

signal.c

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next

2013-05-01 14:08:52 -07:00

smp.c

kernel/smp.c: cleanups

2013-04-30 17:04:03 -07:00

smpboot.c

kthread: Prevent unpark race which puts threads on the wrong cpu

2013-04-12 14:18:43 +02:00

smpboot.h

smpboot: Provide infrastructure for percpu hotplug threads

2012-08-13 17:01:07 +02:00

softirq.c

Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-07-02 16:14:35 -07:00

spinlock.c

locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage

2012-03-23 13:18:57 +01:00

srcu.c

srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock()

2013-02-07 15:19:36 -08:00

stacktrace.c

…

stop_machine.c

stop_machine: Mark per cpu stopper enabled early

2013-02-26 22:25:17 +01:00

sys_ni.c

unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE

2013-05-09 13:46:38 -04:00

sys.c

reboot: rigrate shutdown/reboot to boot cpu

2013-06-12 16:29:44 -07:00

sysctl_binary.c

switch compat_sys_sysctl to COMPAT_SYSCALL_DEFINE

2013-05-09 14:53:20 -04:00

sysctl.c

perf: Drop sample rate when sampling is too slow

2013-06-23 11:52:57 +02:00

task_work.c

task_work: task_work_add() should not succeed after exit_task_work()

2012-09-13 16:47:34 +02:00

taskstats.c

taskstats: cgroupstats_user_cmd() may leak on error

2012-10-06 03:05:31 +09:00

test_kprobes.c

kernel/: rename random32() to prandom_u32()

2013-04-29 18:28:42 -07:00

time.c

sched: Rename sched.c as sched/core.c in comments and Documentation

2013-06-19 12:58:42 +02:00

timeconst.bc

kernel: Replace timeconst.pl with a bc script

2013-02-16 23:17:25 +01:00

timer.c

Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-05-15 14:05:17 -07:00

tracepoint.c

Merge tag 'trace-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2013-04-29 13:55:38 -07:00

tsacct.c

cputime: Use accessors to read task cputime stats

2013-01-27 19:23:31 +01:00

uid16.c

make SYSCALL_DEFINE<n>-generated wrappers do asmlinkage_protect

2013-03-03 22:58:33 -05:00

up.c

…

user_namespace.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2013-05-01 17:51:54 -07:00

user-return-notifier.c

hlist: drop the node parameter from iterators

2013-02-27 19:10:24 -08:00

user.c

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2013-05-01 17:51:54 -07:00

utsname_sysctl.c

kernel/utsname_sysctl.c: put get/get_uts() into CONFIG_PROC_SYSCTL code block

2013-02-27 19:10:22 -08:00

utsname.c

proc: Split the namespace stuff out into linux/proc_ns.h

2013-05-01 17:29:39 -04:00

wait.c

Add wait_on_atomic_t() and wake_up_atomic_t()

2013-05-15 13:50:38 +01:00

watchdog.c

watchdog: Add comments to explain the watchdog_disabled variable

2013-03-14 08:24:05 +01:00

workqueue_internal.h

sched: Rename sched.c as sched/core.c in comments and Documentation

2013-06-19 12:58:42 +02:00

workqueue.c

workqueue: don't perform NUMA-aware allocations on offline nodes in wq_numa_init()

2013-05-15 14:24:24 -07:00