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authorPeter Zijlstra <peterz@infradead.org>2016-02-24 18:45:46 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-04-20 15:40:45 +0900
commit1931344f79a1fe720c0f98ce78df3823bf3bef17 (patch)
tree3164b8408aa998c4c9efec7356615037ba96cc3e
parentebe9c20f8d6e7b499b515ed4b3326d3faa226848 (diff)
downloadlwn-1931344f79a1fe720c0f98ce78df3823bf3bef17.tar.gz
lwn-1931344f79a1fe720c0f98ce78df3823bf3bef17.zip
perf: Cure event->pending_disable race
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>
-rw-r--r--kernel/events/core.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index bfd91336e888..cbd549ee09e4 100644
--- 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--;