Commit c0d1d2bf authored Jun 08, 2007 by Thomas Gleixner Committed by Linus Torvalds Jun 08, 2007

rt-mutex: fix stale return value



Alexey Kuznetsov found some problems in the pi-futex code.

The major problem is a stale return value in rt_mutex_slowlock():

When the pi chain walk returns -EDEADLK, but the waiter was woken up during
the phases where the locks were dropped, the rtmutex could be acquired, but
due to the stale return value -EDEADLK returned to the caller.

Reset the return value in the retry path.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 51b94d2a

kernel/rtmutex.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -636,9 +636,16 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
		* all over without going into schedule to try
		* to get the lock now:
		*/
		if (unlikely(!waiter.task))
		if (unlikely(!waiter.task)) {
		/*
		* Reset the return value. We might
		* have returned with -EDEADLK and the
		* owner released the lock while we
		* were walking the pi chain.
		*/
		ret = 0;
		continue;

		}
		if (unlikely(ret))
		break;
		}