[GIT PULL] locking fix

From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Borislav Petkov <bp@alien8.de>
Subject: [GIT PULL] locking fix
Date: Sat, 11 Feb 2023 09:54:28 +0100	[thread overview]
Message-ID: <Y+dXxGNISTLdmh/U@gmail.com> (raw)

Linus,

Please pull the latest locking/urgent git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-2023-02-11

   # HEAD: db370a8b9f67ae5f17e3d5482493294467784504 rtmutex: Ensure that the top waiter is always woken up

Fix an rtmutex missed-wakeup bug.

 Thanks,

	Ingo

------------------>
Wander Lairson Costa (1):
      rtmutex: Ensure that the top waiter is always woken up


 kernel/locking/rtmutex.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 010cf4e6d0b8..728f434de2bb 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -901,8 +901,9 @@ static int __sched rt_mutex_adjust_prio_chain(struct task_struct *task,
 		 * then we need to wake the new top waiter up to try
 		 * to get the lock.
 		 */
-		if (prerequeue_top_waiter != rt_mutex_top_waiter(lock))
-			wake_up_state(waiter->task, waiter->wake_state);
+		top_waiter = rt_mutex_top_waiter(lock);
+		if (prerequeue_top_waiter != top_waiter)
+			wake_up_state(top_waiter->task, top_waiter->wake_state);
 		raw_spin_unlock_irq(&lock->wait_lock);
 		return 0;
 	}
