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Subject: Re: [PATCH] sched: make sure sched_child_runs_first WORK
From: Peter Zijlstra <peterz@infradead.org>
To: marywangran <marywangran@gmail.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>
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	 <e82940b20904280426j53ff8be7h3caeed84a02bbfe9@mail.gmail.com>
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Date: Tue, 28 Apr 2009 13:53:32 +0200
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On Tue, 2009-04-28 at 19:26 +0800, marywangran wrote:


> Signed-off-by: Ya Zhao <marywangran@gmail.com>
> ---
> --- linux-2.6.28.1/kernel/sched_fair.c.orig     2009-04-28
> 22:26:00.000000000 +0800
> +++ linux-2.6.28.1/kernel/sched_fair.c  2009-04-28 22:34:49.000000000 +0800
> @@ -1628,12 +1628,13 @@ static void task_new_fair(struct rq *rq,
> 
>        /* 'curr' will be NULL if the child belongs to a different group */
>        if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
> -                       curr && curr->vruntime < se->vruntime) {
> +                      curr){
>                /*
>                 * Upon rescheduling, sched_class::put_prev_task() will place
>                 * 'current' within the tree based on its new key value.
>                 */
> -               swap(curr->vruntime, se->vruntime);
> +               if( curr->vruntime < se->vruntime )
> +                       swap(curr->vruntime, se->vruntime);
>                resched_task(rq->curr);
>        }

Aside from the style issue the patch seems sensible enough.

Thing is, do we really care about child runs first?