linux/debian/patches-rt/0152-locking-rtmutex-re-init-the-wait_lock-in-rt_mutex_in.patch

From ae27c05c699a2836bb476966ecbea706b7f36ea1 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 16 Nov 2017 16:48:48 +0100
Subject: [PATCH 152/325] locking/rtmutex: re-init the wait_lock in
 rt_mutex_init_proxy_locked()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.115-rt48.tar.xz

We could provide a key-class for the lockdep (and fixup all callers) or
move the init to all callers (like it was) in order to avoid lockdep
seeing a double-lock of the wait_lock.

Reported-by: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/locking/rtmutex.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index b38c3a92dce8..94788662b2f2 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -2281,6 +2281,14 @@ void rt_mutex_init_proxy_locked(struct rt_mutex *lock,
 				struct task_struct *proxy_owner)
 {
 	__rt_mutex_init(lock, NULL, NULL);
+#ifdef CONFIG_DEBUG_SPINLOCK
+	/*
+	 * get another key class for the wait_lock. LOCK_PI and UNLOCK_PI is
+	 * holding the ->wait_lock of the proxy_lock while unlocking a sleeping
+	 * lock.
+	 */
+	raw_spin_lock_init(&lock->wait_lock);
+#endif
 	debug_rt_mutex_proxy_lock(lock, proxy_owner);
 	rt_mutex_set_owner(lock, proxy_owner);
 }
-- 
2.25.1