linux-kernel - [tip:core/locking] sched: remove extra call overhead for schedule()

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Date:	Fri, 13 Mar 2009 13:00:29 GMT
From:	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, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:core/locking] sched: remove extra call overhead for schedule()

Commit-ID:  e690e5337d953a0936a9735424a454ec21bae0a5
Gitweb:     http://git.kernel.org/tip/e690e5337d953a0936a9735424a454ec21bae0a5
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Fri, 13 Mar 2009 12:21:26 +0100
Commit:     Ingo Molnar <mingo@...e.hu>
CommitDate: Fri, 13 Mar 2009 13:55:17 +0100

sched: remove extra call overhead for schedule()

Lai Jiangshan's patch reminded me that I promised Nick to remove
that extra call overhead in schedule().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <20090313112300.927414207@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/mutex.c |    4 +++-
 kernel/sched.c |   12 ++++--------
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/kernel/mutex.c b/kernel/mutex.c
index 5d79781..e1fb735 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -248,7 +248,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 
 		/* didnt get the lock, go to sleep: */
 		spin_unlock_mutex(&lock->wait_lock, flags);
-		__schedule();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
 		spin_lock_mutex(&lock->wait_lock, flags);
 	}
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 8549d48..01275cb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4543,13 +4543,15 @@ pick_next_task(struct rq *rq, struct task_struct *prev)
 /*
  * schedule() is the main scheduler function.
  */
-asmlinkage void __sched __schedule(void)
+asmlinkage void __sched schedule(void)
 {
 	struct task_struct *prev, *next;
 	unsigned long *switch_count;
 	struct rq *rq;
 	int cpu;
 
+need_resched:
+	preempt_disable();
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
 	rcu_qsctr_inc(cpu);
@@ -4606,15 +4608,9 @@ need_resched_nonpreemptible:
 
 	if (unlikely(reacquire_kernel_lock(current) < 0))
 		goto need_resched_nonpreemptible;
-}
 
-asmlinkage void __sched schedule(void)
-{
-need_resched:
-	preempt_disable();
-	__schedule();
 	preempt_enable_no_resched();
-	if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
+	if (need_resched())
 		goto need_resched;
 }
 EXPORT_SYMBOL(schedule);
--
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