perf_events: Fix read() bogus counts when in error state
When a pinned group cannot be scheduled it goes into error state. Normally a group cannot go out of error state without being explicitly re-enabled or disabled. There was a bug in per-thread mode, whereby upon termination of the thread, the group would transition from error to off leading to bogus counts and timing information returned by read(). Fix it by clearing the error state. Signed-off-by: Stephane Eranian <eranian@google.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: perfmon2-devel@lists.sourceforge.net LKML-Reference: <4b0eb9ce.0508d00a.573b.ffffeab6@mx.google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -338,6 +338,15 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
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event->group_leader->nr_siblings--;
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update_event_times(event);
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/*
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* If event was in error state, then keep it
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* that way, otherwise bogus counts will be
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* returned on read(). The only way to get out
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* of error state is by explicit re-enabling
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* of the event
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*/
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if (event->state > PERF_EVENT_STATE_OFF)
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event->state = PERF_EVENT_STATE_OFF;
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/*
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