rt_mutex: restore wait_lock init in __rt_mutex_init

From: Darren Hart <dvhart@linux.intel.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: Darren Hart <dvhart@linux.intel.com>,
	Maarten Lankhorst <m.b.lankhorst@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: rt_mutex: restore wait_lock init in __rt_mutex_init
Date: Wed, 27 Jul 2011 01:18:31 -0700	[thread overview]
Message-ID: <1311754711-19577-1-git-send-email-dvhart@linux.intel.com> (raw)

Without the raw_spin_lock_init(), the wait_lock does not get properly
initialized with CONFIG_DEBUG_SPINLOCK. This can manifest in a BUG() in the
futex requeue_pi path when the pi_state->pi_mutex->wait_lock fails the magic
test in rt_mutex_start_proxy_lock()->raw_spin_lock(&lock->wait_lock).

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Reported-by: Maarten Lankhorst <m.b.lankhorst@gmail.com>
CC: Maarten Lankhorst <m.b.lankhorst@gmail.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Steven Rostedt <rostedt@goodmis.org>

---
 rtmutex.c |    1 +
 1 file changed, 1 insertion(+)

Index: linux-3.0-rt/kernel/rtmutex.c
===================================================================

--- linux-3.0-rt.orig/kernel/rtmutex.c
+++ linux-3.0-rt/kernel/rtmutex.c
@@ -1277,6 +1277,7 @@ EXPORT_SYMBOL_GPL(rt_mutex_destroy);
 void __rt_mutex_init(struct rt_mutex *lock, const char *name)
 {
 	lock->owner = NULL;
+	raw_spin_lock_init(&lock->wait_lock);
 	plist_head_init_raw(&lock->wait_list, &lock->wait_lock);
 
 	debug_rt_mutex_init(lock, name);
