Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 30/37] perf: Cure event->pending_disable race | Date | Mon, 18 Apr 2016 11:26:02 +0900 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra <peterz@infradead.org>
commit 28a967c3a2f99fa3b5f762f25cb2a319d933571b upstream.
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.shishkin@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dvyukov@google.com Cc: eranian@google.com Cc: oleg@redhat.com Cc: panand@redhat.com Cc: sasha.levin@oracle.com Cc: vince@deater.net Link: http://lkml.kernel.org/r/20160224174948.040469884@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/events/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1400,14 +1400,14 @@ 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--;
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