From 44b7f4b98d8877e2a4427f2a2f2e42ae8227a58f Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 13 Dec 2011 20:40:45 +0100 Subject: 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 Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20111213152651.GP20297@mudshark.cambridge.arm.com [ minor edits ] Signed-off-by: Ingo Molnar --- kernel/events/core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'kernel/events') diff --git a/kernel/events/core.c b/kernel/events/core.c index d3b9df5962c2..58690af323e4 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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(); } -- cgit v1.2.3