perf: Fix exit() vs PERF_FORMAT_GROUP
Both Stephane and Corey reported that PERF_FORMAT_GROUP didn't work
as expected if the task the counters were attached to quit before
the read() call.
The cause is that we unconditionally destroy the grouping when we
remove counters from their context. Fix this by only doing this when
we free the counter itself.
Reported-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1273160566.5605.404.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 3d1552d..f13c3db 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -341,6 +341,9 @@
if (event->state > PERF_EVENT_STATE_OFF)
event->state = PERF_EVENT_STATE_OFF;
+ if (event->state > PERF_EVENT_STATE_FREE)
+ return;
+
/*
* If this was a group event with sibling events then
* upgrade the siblings to singleton events by adding them
@@ -1856,6 +1859,8 @@
{
struct perf_event_context *ctx = event->ctx;
+ event->state = PERF_EVENT_STATE_FREE;
+
WARN_ON_ONCE(ctx->parent_ctx);
mutex_lock(&ctx->mutex);
perf_event_remove_from_context(event);