perf: Fix reading in perf_event_read()

542e72fc · Peter Zijlstra <[email protected]> · 2011-01-26 15:38:35 +01:00

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 <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <[email protected]>

Commit: 542e72fc90f5ed9eecb574f80f70868c7f296093
Parents: 9ffdc6c3

Changes

1 files changed · +4 −3

File	Status	Add	Del	Content
kernel/perf_event.c	modified	+4	−3	View file

kernel/perf_event.c

View file

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 852ae8c..999835b 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -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)