From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 11 Jan 2019 21:16:31 +0100
Subject: [PATCH] rtmutex/rwlock: preserve state like a sleeping lock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.25-rt16.tar.xz

The rwlock is spinning while acquiring a lock. Therefore it must become
a sleeping lock on RT and preserve its task state while sleeping and
waiting for the lock to become available.

Reported-by: Joe Korty <Joe.Korty@concurrent-rt.com>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/locking/rwlock-rt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -128,7 +128,7 @@ void __sched __read_rt_lock(struct rt_rw
 	 * That would put Reader1 behind the writer waiting on
 	 * Reader2 to call read_unlock() which might be unbound.
 	 */
-	rt_mutex_init_waiter(&waiter, false);
+	rt_mutex_init_waiter(&waiter, true);
 	rt_spin_lock_slowlock_locked(m, &waiter, flags);
 	/*
 	 * The slowlock() above is guaranteed to return with the rtmutex is
