commit 1ca7b86062ec8473d03c5cdfd336abc8b1c8098c
author Thomas Gleixner <tglx@linutronix.de> Sat Jun 07 09:36:13 2014 +0200
committer Thomas Gleixner <tglx@linutronix.de> Sat Jun 21 22:05:30 2014 +0200
tree 4d4fb16eebac3bac63a317a406e60f78469c3828
parent 3eb65aeadf701976b084e9171e16bb7d1e83fbb0

rtmutex: Simplify remove_waiter()

Exit right away, when the removed waiter was not the top priority
waiter on the lock. Get rid of the extra indent level.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>

kernel/locking/rtmutex.c

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index ed88021..1e8fdab 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -917,9 +917,9 @@
 static void remove_waiter(struct rt_mutex *lock,
 			  struct rt_mutex_waiter *waiter)
 {
-	int first = (waiter == rt_mutex_top_waiter(lock));
+	bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock));
 	struct task_struct *owner = rt_mutex_owner(lock);
-	struct rt_mutex *next_lock = NULL;
+	struct rt_mutex *next_lock;
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&current->pi_lock, flags);
@@ -927,29 +927,31 @@
 	current->pi_blocked_on = NULL;
 	raw_spin_unlock_irqrestore(&current->pi_lock, flags);
 
-	if (!owner)
+	/*
+	 * Only update priority if the waiter was the highest priority
+	 * waiter of the lock and there is an owner to update.
+	 */
+	if (!owner || !is_top_waiter)
 		return;
 
-	if (first) {
+	raw_spin_lock_irqsave(&owner->pi_lock, flags);
 
-		raw_spin_lock_irqsave(&owner->pi_lock, flags);
+	rt_mutex_dequeue_pi(owner, waiter);
 
-		rt_mutex_dequeue_pi(owner, waiter);
+	if (rt_mutex_has_waiters(lock))
+		rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock));
 
-		if (rt_mutex_has_waiters(lock)) {
-			struct rt_mutex_waiter *next;
+	__rt_mutex_adjust_prio(owner);
 
-			next = rt_mutex_top_waiter(lock);
-			rt_mutex_enqueue_pi(owner, next);
-		}
-		__rt_mutex_adjust_prio(owner);
+	/* Store the lock on which owner is blocked or NULL */
+	next_lock = task_blocked_on_lock(owner);
 
-		/* Store the lock on which owner is blocked or NULL */
-		next_lock = task_blocked_on_lock(owner);
+	raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
 
-		raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
-	}
-
+	/*
+	 * Don't walk the chain, if the owner task is not blocked
+	 * itself.
+	 */
 	if (!next_lock)
 		return;