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perf_events: Fix read() bogus counts when in error state

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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>
This commit is contained in:
Stephane Eranian 2009-11-26 09:24:30 -08:00 committed by Ingo Molnar
parent 4d795fb17a
commit b2e74a265d
1 changed files with 10 additions and 1 deletions
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11
kernel/perf_event.c
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@ -338,7 +338,16 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
event->group_leader->nr_siblings--;
update_event_times(event);
event->state = PERF_EVENT_STATE_OFF;
/*
* If event was in error state, then keep it
* that way, otherwise bogus counts will be
* returned on read(). The only way to get out
* of error state is by explicit re-enabling
* of the event
*/
if (event->state > PERF_EVENT_STATE_OFF)
event->state = PERF_EVENT_STATE_OFF;
/*
* If this was a group event with sibling events then