From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 7 Sep 2017 12:38:47 +0200
Subject: locking/rtmutex: don't drop the wait_lock twice

Since the futex rework, __rt_mutex_start_proxy_lock() does no longer
acquire the wait_lock so it must not drop it. Otherwise the lock is not
only unlocked twice but also the preemption counter is underflown.

It is okay to remove that line because this function does not disable
interrupts nor does it acquire the ->wait_lock. The caller does this so it is
wrong do it here (after the futex rework).

Cc: rt-stable@vger.kernel.org #v4.9.18-rt14+
Reported-by: Gusenleitner Klaus <gus@keba.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/locking/rtmutex.c |    1 -
 1 file changed, 1 deletion(-)

--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1745,7 +1745,6 @@ int __rt_mutex_start_proxy_lock(struct r
 	raw_spin_lock(&task->pi_lock);
 	if (task->pi_blocked_on) {
 		raw_spin_unlock(&task->pi_lock);
-		raw_spin_unlock_irq(&lock->wait_lock);
 		return -EAGAIN;
 	}
 	task->pi_blocked_on = PI_REQUEUE_INPROGRESS;