linux-kernel - Re: [PATCH] sched: fix idle at tick

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Message-Id: <200703061841.08343.kernel@kolivas.org>
Date:	Tue, 6 Mar 2007 18:41:08 +1100
From:	Con Kolivas <kernel@...ivas.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"J.A. Magallón" <jamagallon@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: fix idle at tick

On Tuesday 06 March 2007 18:02, Andrew Morton wrote:
> On Tue, 6 Mar 2007 17:25:36 +1100 Con Kolivas <kernel@...ivas.org> wrote:
> > Signed-off-by: Con Kolivas <kernel@...ivas.org>
> > ---
> >  kernel/sched.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Index: linux-2.6.21-rc2-mm1-base/kernel/sched.c
> > ===================================================================
> > --- linux-2.6.21-rc2-mm1-base.orig/kernel/sched.c	2007-03-06
> > 17:19:17.000000000 +1100 +++
> > linux-2.6.21-rc2-mm1-base/kernel/sched.c	2007-03-06 17:20:40.000000000
> > +1100 @@ -3444,7 +3444,7 @@ void scheduler_tick(void)
> >
> >  	update_cpu_clock(p, rq, now);
> >
> > -	if (idle_at_tick)
> > +	if (!idle_at_tick)
> >  		task_running_tick(rq, p);
> >  #ifdef CONFIG_SMP
> >  	update_load(rq);
>
> Looks right, thanks.  The original patch had
>
> -	if (p == rq->idle)
> +	if (idle_at_tick)
>  		/* Task on the idle queue */
>  		wake_priority_sleeper(rq);
>  	else
>  		task_running_tick(rq, p);
>
> but it got damaged by smt-nice removal.

I gathered something like that happened. If it wasn't clear this change caused 
massive scheduler damage with no cpu accounting whatsoever occurring. I 
recommend putting it in your hotfixes/ dir if you're not planning an -mm2 
soon.

-- 
-ck
-
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