[tip:sched/core] sched: Avoid going ahead if ->cpus_allowed is not changed

[tip-bot for Yong Zhang <yong.zhang0@gmail.com>]

Commit-ID:  db44fc017d5989302713ab4e7f9e922b648f4b59
Gitweb:     http://git.kernel.org/tip/db44fc017d5989302713ab4e7f9e922b648f4b59
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Mon, 9 May 2011 22:07:05 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 16 May 2011 11:01:18 +0200

sched: Avoid going ahead if ->cpus_allowed is not changed

If cpumask_equal(&p->cpus_allowed, new_mask) is true, seems
there is no reason to prevent set_cpus_allowed_ptr() return
directly.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Acked-by: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110509140705.GA2219@zhy
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/sched.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index b8b9a7d..70bec4f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5946,13 +5946,15 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
 
 	rq = task_rq_lock(p, &flags);
 
+	if (cpumask_equal(&p->cpus_allowed, new_mask))
+		goto out;
+
 	if (!cpumask_intersects(new_mask, cpu_active_mask)) {
 		ret = -EINVAL;
 		goto out;
 	}
 
-	if (unlikely((p->flags & PF_THREAD_BOUND) && p != current &&
-		     !cpumask_equal(&p->cpus_allowed, new_mask))) {
+	if (unlikely((p->flags & PF_THREAD_BOUND) && p != current)) {
 		ret = -EINVAL;
 		goto out;
 	}