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From: Frederic Weisbecker <fweisbec@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH 1/2] sched: Drop the need_resched() loop from cond_resched()
Date: Fri, 10 Jul 2009 17:24:27 +0200	[thread overview]
Message-ID: <20090710152425.GB5318@nowhere> (raw)
In-Reply-To: <200907101717.39460.arnd@arndb.de>

On Fri, Jul 10, 2009 at 05:17:38PM +0200, Arnd Bergmann wrote:
> On Friday 10 July 2009, Frederic Weisbecker wrote:
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -6613,11 +6613,9 @@ static void __cond_resched(void)
> >          * PREEMPT_ACTIVE, which could trigger a second
> >          * cond_resched() call.
> >          */
> > -       do {
> > -               add_preempt_count(PREEMPT_ACTIVE);
> > -               schedule();
> > -               sub_preempt_count(PREEMPT_ACTIVE);
> > -       } while (need_resched());
> > +       add_preempt_count(PREEMPT_ACTIVE);
> > +       schedule();
> > +       sub_preempt_count(PREEMPT_ACTIVE);
> >  }
> >  
> 
> If you drop the loop, then you should also remove the comment that
> explains why it was put there.
> 
> 	Arnd <><

Hmm, these comments seem to actually explain why we do the PREEMPT_ACTIVE
trick, which is to prevent from cond_resched() recursion, right?


  reply	other threads:[~2009-07-10 15:24 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-10 14:49 [PATCH 1/2] sched: Drop the need_resched() loop from cond_resched() Frederic Weisbecker
2009-07-10 14:49 ` [PATCH 2/2] sched: Move the sleeping while atomic checks early in cond_resched() Frederic Weisbecker
2009-07-10 14:59   ` Peter Zijlstra
2009-07-10 15:08     ` Frederic Weisbecker
2009-07-10 15:12       ` Peter Zijlstra
2009-07-10 16:10         ` Ingo Molnar
2009-07-10 17:14           ` [PATCH] " Frederic Weisbecker
2009-07-10 17:43             ` Peter Zijlstra
2009-07-10 18:08               ` Frederic Weisbecker
2009-07-10 18:13                 ` Peter Zijlstra
2009-07-10 18:29                   ` Frederic Weisbecker
2009-07-10 15:00 ` [PATCH 1/2] sched: Drop the need_resched() loop from cond_resched() Peter Zijlstra
2009-07-10 15:17 ` Arnd Bergmann
2009-07-10 15:24   ` Frederic Weisbecker [this message]
2009-07-10 15:35     ` Arnd Bergmann
2009-07-10 15:50       ` Frederic Weisbecker
2009-07-10 16:11         ` Ingo Molnar
2009-07-10 16:26           ` Frederic Weisbecker
2009-07-10 17:23           ` [PATCH] sched: Remove obsolete comment in __cond_resched() Frederic Weisbecker

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