linux-kernel - [tip:sched/urgent] sched: Simplify set_task

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Date:	Wed, 16 Dec 2009 18:39:25 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, efault@....de, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:sched/urgent] sched: Simplify set_task_cpu()

Commit-ID:  738d2be4301007f054541c5c4bf7fb6a361c9b3a
Gitweb:     http://git.kernel.org/tip/738d2be4301007f054541c5c4bf7fb6a361c9b3a
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Wed, 16 Dec 2009 18:04:42 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 16 Dec 2009 19:01:59 +0100

sched: Simplify set_task_cpu()

Rearrange code a bit now that its a simpler function.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Mike Galbraith <efault@....de>
LKML-Reference: <20091216170518.269101883@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched.c |   13 +++++--------
 1 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index f92ce63..8a2bfd3 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2034,11 +2034,8 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
 	return delta < (s64)sysctl_sched_migration_cost;
 }
 
-
 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 {
-	int old_cpu = task_cpu(p);
-
 #ifdef CONFIG_SCHED_DEBUG
 	/*
 	 * We should never call set_task_cpu() on a blocked task,
@@ -2049,11 +2046,11 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 
 	trace_sched_migrate_task(p, new_cpu);
 
-	if (old_cpu != new_cpu) {
-		p->se.nr_migrations++;
-		perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS,
-				     1, 1, NULL, 0);
-	}
+	if (task_cpu(p) == new_cpu)
+		return;
+
+	p->se.nr_migrations++;
+	perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 1, NULL, 0);
 
 	__set_task_cpu(p, new_cpu);
 }
--
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