Re: [perfmon2] [PATCH] perf_events: fix read() bogus counts when in error state
Status: Beta
Brought to you by:
seranian
From: Peter Z. <pe...@in...> - 2009-11-26 17:37:19
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On Thu, 2009-11-26 at 09:24 -0800, Stephane Eranian wrote: > 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(). > Signed-off-by: Stephane Eranian <er...@go...> Right, good catch, totally forgot about error state :/ Acked-by: Peter Zijlstra <a.p...@ch...> > --- > perf_event.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/kernel/perf_event.c b/kernel/perf_event.c > index 0b0d5f7..7a8bb5b 100644 > --- a/kernel/perf_event.c > +++ b/kernel/perf_event.c > @@ -333,7 +333,16 @@ 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 |