Commit c0d1d2bf authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds

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: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarIngo 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 51b94d2a
...@@ -636,9 +636,16 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, ...@@ -636,9 +636,16 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
* all over without going into schedule to try * all over without going into schedule to try
* to get the lock now: * 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; continue;
}
if (unlikely(ret)) if (unlikely(ret))
break; break;
} }
......
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