linux-kernel - [tip:locking/urgent] locking/rtmutex: Remove unnecessary priority adjustment

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Date:   Thu, 13 Jul 2017 02:48:42 -0700
From:   tip-bot for Alex Shi <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     bigeasy@...utronix.de, alex.shi@...aro.org, juri.lelli@....com,
        tglx@...utronix.de, rostedt@...dmis.org, peterz@...radead.org,
        mathieu.poirier@...aro.org, hpa@...or.com,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        mingo@...nel.org
Subject: [tip:locking/urgent] locking/rtmutex: Remove unnecessary priority
 adjustment

Commit-ID:  69f0d429c413fe96db2c187475cebcc6e3a8c7f5
Gitweb:     http://git.kernel.org/tip/69f0d429c413fe96db2c187475cebcc6e3a8c7f5
Author:     Alex Shi <alex.shi@...aro.org>
AuthorDate: Thu, 13 Jul 2017 14:18:24 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 13 Jul 2017 11:44:06 +0200

locking/rtmutex: Remove unnecessary priority adjustment

We don't need to adjust priority before adding a new pi_waiter, the
priority only needs to be updated after pi_waiter change or task
priority change.

Steven Rostedt pointed out:

  "Interesting, I did some git mining and this was added with the original
   entry of the rtmutex.c (23f78d4a03c5). Looking at even that version, I
   don't see the purpose of adjusting the task prio here. It is done
   before anything changes in the task."

Signed-off-by: Alex Shi <alex.shi@...aro.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Sebastian Siewior <bigeasy@...utronix.de>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1499926704-28841-1-git-send-email-alex.shi@linaro.org
[ Enhance the changelog. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/locking/rtmutex.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 7806989..649dc9d 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -963,7 +963,6 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 		return -EDEADLK;
 
 	raw_spin_lock(&task->pi_lock);
-	rt_mutex_adjust_prio(task);
 	waiter->task = task;
 	waiter->lock = lock;
 	waiter->prio = task->prio;