perf: Fix reading in perf_event_read()
authorPeter Zijlstra <a.p.zijlstra@chello.nl>
Wed, 26 Jan 2011 14:38:35 +0000 (15:38 +0100)
committerIngo Molnar <mingo@elte.hu>
Thu, 3 Feb 2011 11:15:46 +0000 (12:15 +0100)
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>
kernel/perf_event.c

index 852ae8c66502129d10a6ffeb4b53e40a0e5c3568..999835b6112bc0705e6a511a63889a89c920b9d7 100644 (file)
@@ -1901,11 +1901,12 @@ static void __perf_event_read(void *info)
                return;
 
        raw_spin_lock(&ctx->lock);
-       update_context_time(ctx);
+       if (ctx->is_active)
+               update_context_time(ctx);
        update_event_times(event);
+       if (event->state == PERF_EVENT_STATE_ACTIVE)
+               event->pmu->read(event);
        raw_spin_unlock(&ctx->lock);
-
-       event->pmu->read(event);
 }
 
 static inline u64 perf_event_count(struct perf_event *event)