From f146b8d5a18ed1cc966e92ecd41ded4f862f2933 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 10 Jun 2011 15:08:55 +0200
Subject: [PATCH] --- yaml --- r: 257159 b: refs/heads/master c:
 307bf9803f25a8a3f53c1012110fb74e2f893eb0 h: refs/heads/master i:   257157:
 2631663f428dbe60bd3935d9bb2c3639da16490a   257155:
 a1760ea5c2688aeaebfd5882c897bf21a621fce1   257151:
 713fc05bc54908e20664b8f16458949d9bb5ec83 v: v3

---
 [refs]               |  2 +-
 trunk/kernel/sched.c | 25 +++++++++----------------
 2 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/[refs] b/[refs]
index 3e40e6bc9a25..3398c6562bcf 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2a46dae38087e62dd5fb08a6dadf1407717ed13c
+refs/heads/master: 307bf9803f25a8a3f53c1012110fb74e2f893eb0
diff --git a/trunk/kernel/sched.c b/trunk/kernel/sched.c
index 59252754fbe0..e355ee72e83f 100644
--- a/trunk/kernel/sched.c
+++ b/trunk/kernel/sched.c
@@ -4306,11 +4306,8 @@ EXPORT_SYMBOL(schedule);
 
 static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
 {
-	bool ret = false;
-
-	rcu_read_lock();
 	if (lock->owner != owner)
-		goto fail;
+		return false;
 
 	/*
 	 * Ensure we emit the owner->on_cpu, dereference _after_ checking
@@ -4320,11 +4317,7 @@ static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
 	 */
 	barrier();
 
-	ret = owner->on_cpu;
-fail:
-	rcu_read_unlock();
-
-	return ret;
+	return owner->on_cpu;
 }
 
 /*
@@ -4336,21 +4329,21 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
 	if (!sched_feat(OWNER_SPIN))
 		return 0;
 
+	rcu_read_lock();
 	while (owner_running(lock, owner)) {
 		if (need_resched())
-			return 0;
+			break;
 
 		arch_mutex_cpu_relax();
 	}
+	rcu_read_unlock();
 
 	/*
-	 * If the owner changed to another task there is likely
-	 * heavy contention, stop spinning.
+	 * We break out the loop above on need_resched() and when the
+	 * owner changed, which is a sign for heavy contention. Return
+	 * success only when lock->owner is NULL.
 	 */
-	if (lock->owner)
-		return 0;
-
-	return 1;
+	return lock->owner == NULL;
 }
 #endif