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rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() 

mark_wakeup_next_waiter() already disables preemption, doing so again
leaves us with an unpaired preempt_disable().

Fixes: 2a1c602994 ("rtmutex: Deboost before waking up the top waiter")
Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1491379707.6538.2.camel@gmx.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Mike Galbraith 2017-04-05 10:08:27 +02:00 committed by Thomas Gleixner
parent 19830e5524
commit def34eaae5
1 changed files with 5 additions and 5 deletions
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10
kernel/locking/rtmutex.c
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@ -1581,13 +1581,13 @@ bool __sched __rt_mutex_futex_unlock(struct rt_mutex *lock,
return false; /* done */
}
mark_wakeup_next_waiter(wake_q, lock);
/*
* We've already deboosted, retain preempt_disabled when dropping
* the wait_lock to avoid inversion until the wakeup. Matched
* by rt_mutex_postunlock();
* We've already deboosted, mark_wakeup_next_waiter() will
* retain preempt_disabled when we drop the wait_lock, to
* avoid inversion prior to the wakeup. preempt_disable()
* therein pairs with rt_mutex_postunlock().
*/
preempt_disable();
mark_wakeup_next_waiter(wake_q, lock);
return true; /* call postunlock() */
}