linux-kernel - [PATCH RT] rtmutex/rwlock: preserve state like a sleeping lock

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Date:   Fri, 11 Jan 2019 21:22:57 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Joe Korty <Joe.Korty@...current-rt.com>
Cc:     "julia@...com" <julia@...com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH RT] rtmutex/rwlock: preserve state like a sleeping lock

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.

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

diff --git a/kernel/locking/rwlock-rt.c b/kernel/locking/rwlock-rt.c
index f2e155b2c4a8b..c3b91205161cc 100644
--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -128,7 +128,7 @@ void __sched __read_rt_lock(struct rt_rw_lock *lock)
 	 * 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
-- 
2.20.1