Commit 21e3424e authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Greg Kroah-Hartman

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 woken up path.

Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarChris Wright <chrisw@sous-sol.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent b6b364ea
......@@ -659,9 +659,16 @@ 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;
}
......
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