perf: Fix free_event()

With the context rework stuff we can actually end up freeing an event
before it gets attached to a context.

Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index bc46bff69620..440f9ca067b2 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2150,7 +2150,9 @@ static void free_event(struct perf_event *event)
         if (event->destroy)
                 event->destroy(event);
 
-        put_ctx(event->ctx);
+        if (event->ctx)
+                put_ctx(event->ctx);
+
         call_rcu(&event->rcu_head, free_event_rcu);
 }