Commit-ID: 28a967c3a2f99fa3b5f762f25cb2a319d933571b Gitweb: http://git.kernel.org/tip/28a967c3a2f99fa3b5f762f25cb2a319d933571b Author: Peter Zijlstra <pet...@infradead.org> AuthorDate: Wed, 24 Feb 2016 18:45:46 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 25 Feb 2016 08:42:34 +0100
perf: Cure event->pending_disable race Because event_sched_out() checks event->pending_disable _before_ actually disabling the event, it can happen that the event fires after it checks but before it gets disabled. This would leave event->pending_disable set and the queued irq_work will try and process it. However, if the event trigger was during schedule(), the event might have been de-scheduled by the time the irq_work runs, and perf_event_disable_local() will fail. Fix this by checking event->pending_disable _after_ we call event->pmu->del(). This depends on the latter being a compiler barrier, such that the compiler does not lift the load and re-creates the problem. Tested-by: Alexander Shishkin <alexander.shish...@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reviewed-by: Alexander Shishkin <alexander.shish...@linux.intel.com> Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Jiri Olsa <jo...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: dvyu...@google.com Cc: eran...@google.com Cc: o...@redhat.com Cc: pan...@redhat.com Cc: sasha.le...@oracle.com Cc: vi...@deater.net Link: http://lkml.kernel.org/r/20160224174948.040469...@infradead.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/events/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index ea064ca..de14b67 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1696,14 +1696,14 @@ event_sched_out(struct perf_event *event, perf_pmu_disable(event->pmu); + event->tstamp_stopped = tstamp; + event->pmu->del(event, 0); + event->oncpu = -1; event->state = PERF_EVENT_STATE_INACTIVE; if (event->pending_disable) { event->pending_disable = 0; event->state = PERF_EVENT_STATE_OFF; } - event->tstamp_stopped = tstamp; - event->pmu->del(event, 0); - event->oncpu = -1; if (!is_software_event(event)) cpuctx->active_oncpu--;
