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perf: Fix reading in perf_event_read()

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It is quite possible for the event to have been disabled between
perf_event_read() sending the IPI and the CPU servicing the IPI and
calling __perf_event_read(), hence revalidate the state.

Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2011-01-26 15:38:35 +01:00 committed by Ingo Molnar
parent 9ffdc6c37d
commit 542e72fc90
1 changed files with 4 additions and 3 deletions
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7
kernel/perf_event.c
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@ -1901,11 +1901,12 @@ static void __perf_event_read(void *info)
return; return;
raw_spin_lock(&ctx->lock); raw_spin_lock(&ctx->lock);
update_context_time(ctx); if (ctx->is_active)
update_context_time(ctx);
update_event_times(event); update_event_times(event);
if (event->state == PERF_EVENT_STATE_ACTIVE)
event->pmu->read(event);
raw_spin_unlock(&ctx->lock); raw_spin_unlock(&ctx->lock);
event->pmu->read(event);
} }
static inline u64 perf_event_count(struct perf_event *event) static inline u64 perf_event_count(struct perf_event *event)