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Groups > linux.kernel > #1736798

[PATCH RT] locking/rtmutex: don't drop the wait_lock twice

From Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Newsgroups linux.kernel
Subject [PATCH RT] locking/rtmutex: don't drop the wait_lock twice
Date 2017-09-21 17:50 +0200
Message-ID <usbTI-2TP-19@gated-at.bofh.it> (permalink)
Organization linux.* mail to news gateway

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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.

Cc: rt-stable@vger.kernel.org
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(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index f03876322d4a..79f49d73e4d0 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -2281,7 +2281,6 @@ int __rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 	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;
-- 
2.14.1

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Thread

[PATCH RT] locking/rtmutex: don't drop the wait_lock twice Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-21 17:50 +0200
  Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice Steven Rostedt <rostedt@goodmis.org> - 2017-09-21 18:40 +0200
    Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-21 18:50 +0200
      Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice Steven Rostedt <rostedt@goodmis.org> - 2017-09-21 19:00 +0200
        Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-21 19:40 +0200
          Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice Steven Rostedt <rostedt@goodmis.org> - 2017-09-21 20:00 +0200
            Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-21 20:20 +0200
              [PATCH RT v2] locking/rtmutex: don't drop the wait_lock twice Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-21 20:50 +0200

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