Messages in this thread Patch in this message | | | Date | Fri, 08 Jun 2007 00:29:17 -0000 | From | Thomas Gleixner <> | Subject | [patch 1/4] rt-mutex: Fix stale return value |
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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>
--- kernel/rtmutex.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
Index: linux-2.6.22-rc4/kernel/rtmutex.c =================================================================== --- linux-2.6.22-rc4.orig/kernel/rtmutex.c 2007-06-08 01:39:38.000000000 +0200 +++ linux-2.6.22-rc4/kernel/rtmutex.c 2007-06-08 01:39:38.000000000 +0200 @@ -636,9 +636,16 @@ rt_mutex_slowlock(struct rt_mutex *lock, * 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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