Commit 44b7f4b9 authored Dec 13, 2011 by Will Deacon Committed by Ingo Molnar Dec 14, 2011

perf events: Fix ring_buffer_wakeup() brown paperbag bug



Commit 10c6db11 ("perf: Fix loss of notification with multi-event")
seems to unconditionally dereference event->rb in the wakeup handler,
this is wrong, there might not be a buffer attached.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111213152651.GP20297@mudshark.cambridge.arm.com


[ minor edits ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 373da0a2

kernel/events/core.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -3558,9 +3558,13 @@ static void ring_buffer_wakeup(struct perf_event *event)

		rcu_read_lock();
		rb = rcu_dereference(event->rb);
		list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
		if (!rb)
		goto unlock;

		list_for_each_entry_rcu(event, &rb->event_list, rb_entry)
		wake_up_all(&event->waitq);
		}

		unlock:
		rcu_read_unlock();
		}

Admin message