linux-kernel - [PATCH] sched: remove rcu_read_lock from wake

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Message-ID: <20110607101251.777.34547.stgit@IBM-009124035060.in.ibm.com>
Date:	Tue, 07 Jun 2011 15:43:22 +0530
From:	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>
To:	peterz@...radead.org, mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] sched: remove rcu_read_lock from wake_affine

wake_affine is called from one path: select_task_rq_fair, which already has
rcu read lock held.

Signed-off-by: Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com>
---
 kernel/sched_fair.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 354e26b..0bfec93 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1461,6 +1461,7 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu,
 
 #endif
 
+/* Assumes rcu_read_lock is held */
 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
 {
 	s64 this_load, load;
@@ -1481,7 +1482,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
 	 * effect of the currently running task from the load
 	 * of the current CPU:
 	 */
-	rcu_read_lock();
 	if (sync) {
 		tg = task_group(current);
 		weight = current->se.load.weight;
@@ -1517,7 +1517,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
 		balanced = this_eff_load <= prev_eff_load;
 	} else
 		balanced = true;
-	rcu_read_unlock();
 
 	/*
 	 * If the currently running task will sleep within

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