linux-kernel - [patch 1/2] Re: [PATCH] scheduler: introduce SCHED_RESET_ON

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Date:	Wed, 17 Jun 2009 10:46:01 +0200
From:	Mike Galbraith <efault@....de>
To:	Lennart Poettering <mzxreary@...inter.de>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: [patch 1/2] Re: [PATCH] scheduler: introduce SCHED_RESET_ON_FORK
 scheduling policy flag, fourth try

On Tue, 2009-06-16 at 18:47 +0200, Lennart Poettering wrote:
> On Tue, 16.06.09 11:05, Mike Galbraith (efault@....de) wrote:
> 
> > I think it's cleaner to keep reset_on_fork functionality separate.
> > Thoughts on the below?
> 
> Looks good to me!

OK, I'll submit then, splitting cleanup from functionality addition.

commit 58e1710a8a525e0fb1f4c608d5f73377fb56c893
Author: Mike Galbraith <efault@....de>
Date:   Wed Jun 17 10:16:26 2009 +0200

    sched: SCHED_RESET_ON_FORK cleanup.
    
    Make SCHED_RESET_ON_FORK sched_fork() bits a self-contained unlikely code path.
    
    Signed-off-by: Mike Galbraith <efault@....de>
    Cc: Ingo Molnar <mingo@...e.hu>
    Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
    Cc: Lennart Poettering <mzxreary@...inter.de>
    LKML-Reference: <new-submission>
---
 kernel/sched.c |   34 ++++++++++++++++++----------------
 1 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 095892c..3c27e44 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2613,28 +2613,30 @@ void sched_fork(struct task_struct *p, int clone_flags)
 	set_task_cpu(p, cpu);
 
 	/*
-	 * Revert to default priority/policy on fork if requested. Make sure we
-	 * do not leak PI boosting priority to the child.
+	 * Make sure we do not leak PI boosting priority to the child.
 	 */
-	if (current->sched_reset_on_fork &&
-			(p->policy == SCHED_FIFO || p->policy == SCHED_RR))
-		p->policy = SCHED_NORMAL;
+	p->prio = current->normal_prio;
 
-	if (current->sched_reset_on_fork &&
-			(current->normal_prio < DEFAULT_PRIO))
-		p->prio = DEFAULT_PRIO;
-	else
-		p->prio = current->normal_prio;
+	/*
+	 * Revert to default priority/policy on fork if requested.
+	 */
+	if (unlikely(p->sched_reset_on_fork)) {
+		if (p->policy == SCHED_FIFO || p->policy == SCHED_RR)
+			p->policy = SCHED_NORMAL;
+
+		if (p->normal_prio < DEFAULT_PRIO)
+			p->prio = DEFAULT_PRIO;
+
+		/*
+		 * We don't need the reset flag anymore after the fork. It has
+		 * fulfilled its duty:
+		 */
+		p->sched_reset_on_fork = 0;
+	}
 
 	if (!rt_prio(p->prio))
 		p->sched_class = &fair_sched_class;
 
-	/*
-	 * We don't need the reset flag anymore after the fork. It has
-	 * fulfilled its duty:
-	 */
-	p->sched_reset_on_fork = 0;
-
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
 	if (likely(sched_info_on()))
 		memset(&p->sched_info, 0, sizeof(p->sched_info));


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