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futex: unlock before returning -EFAULT

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Impact: rt-mutex failure case fix

futex_lock_pi can potentially return -EFAULT with the rt_mutex
held.  This seems like the wrong thing to do as userspace should
assume -EFAULT means the lock was not taken.  Even if it could
figure this out, we'd be leaving the pi_state->owner in an
inconsistent state.  This patch unlocks the rt_mutex prior to
returning -EFAULT to userspace.

Build and boot tested on a 4 way Intel x86_64 workstation.
Passes basic pthread_mutex and PI tests out of
ltp/testcases/realtime.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <20090312075606.9856.88729.stgit@Aeon>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Darren Hart 2009-03-12 00:56:06 -07:00 committed by Ingo Molnar
parent 16f4993f4e
commit e8f6386c01
1 changed files with 7 additions and 0 deletions
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7
kernel/futex.c
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@ -1567,6 +1567,13 @@ retry_locked:
}
}
/*
* If fixup_pi_state_owner() faulted and was unable to handle the
* fault, unlock it and return the fault to userspace.
*/
if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current))
rt_mutex_unlock(&q.pi_state->pi_mutex);
/* Unqueue and drop the lock */
unqueue_me_pi(&q);