From b2e74a265ded1a185f762ebaab967e9e0d008dd8 Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Thu, 26 Nov 2009 09:24:30 -0800 Subject: [PATCH] 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 Acked-by: Peter Zijlstra Cc: Paul Mackerras Cc: perfmon2-devel@lists.sourceforge.net LKML-Reference: <4b0eb9ce.0508d00a.573b.ffffeab6@mx.google.com> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index f8c7939c57c..0b9ca2d834d 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -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