linux-kernel - [PATCH] rtmutex: remove unnecessary adjust prio

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Date:   Thu, 13 Jul 2017 14:18:24 +0800
From:   Alex Shi <alex.shi@...aro.org>
To:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org (open list:LOCKING PRIMITIVES)
Cc:     linux-kernel@...r.kernel.org, Alex Shi <alex.shi@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Juri Lelli <juri.lelli@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] rtmutex: remove unnecessary adjust prio

We don't need to adjust prio before new pi_waiter adding. The prio
only need update after pi_waiter change or task priority change.

Steven Rostedt pointed:
"Interesting, I did some git mining and this was added with the original
entry of the rtmutex.c (23f78d4a0). 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>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Sebastian Siewior <bigeasy@...utronix.de>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Juri Lelli <juri.lelli@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
To: linux-kernel@...r.kernel.org
To: Ingo Molnar <mingo@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/locking/rtmutex.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 28cd09e..d1fe41f 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;
-- 
2.7.4