[PATCH RT 07/39] rtmutex: Simplify remove_waiter()

[Steven Rostedt]

3.14.34-rt32-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <t...@linutronix.de>

upstream commit: 1ca7b86062ec8473d03c5cdfd336abc8b1c8098c

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 <t...@linutronix.de>
Reviewed-by: Steven Rostedt <rost...@goodmis.org>
Reviewed-by: Lai Jiangshan <la...@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rost...@goodmis.org>

Conflicts:
        kernel/locking/rtmutex.c
---
 kernel/locking/rtmutex.c | 36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 400026ec7f05..6c74a0525dcb 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -985,7 +985,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock)
 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;
        unsigned long flags;
@@ -995,30 +995,32 @@ static void remove_waiter(struct rt_mutex *lock,
        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 */
-               if (rt_mutex_real_waiter(owner->pi_blocked_on))
-                       next_lock = task_blocked_on_lock(owner);
+       /* Store the lock on which owner is blocked or NULL */
+       if (rt_mutex_real_waiter(owner->pi_blocked_on))
+               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;
 
-- 
2.1.4


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