linux-kernel - Re: CFS and suspend2: hang in atomic copy

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Date:	Thu, 19 Apr 2007 22:32:51 +0200
From:	Christian Hesse <mail@...thworm.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	suspend2-devel@...ts.suspend2.net
Subject: Re: CFS and suspend2: hang in atomic copy

On Thursday 19 April 2007, Ingo Molnar wrote:
> * Christian Hesse <mail@...thworm.de> wrote:
> > I now got some error message from my system:
> >
> > http://www.eworm.de/tmp/cfs-suspend.jpg
>
> ah, this pinpoints a bug: for performance reasons pick_next_task()
> assumes that the runqueue is not empty - which is true for schedule(),
> but not in migrate_dead_tasks(). Does the patch below fix the crash for
> you?
>
>  kernel/sched.c |    2 ++
>  1 file changed, 2 insertions(+)
>
> Index: linux/kernel/sched.c
> ===================================================================
> --- linux.orig/kernel/sched.c
> +++ linux/kernel/sched.c
> @@ -4425,6 +4425,8 @@ static void migrate_dead_tasks(unsigned
>  	struct task_struct *next;
>
>  	for (;;) {
> +		if (!rq->nr_running)
> +			break;
>  		next = pick_next_task(rq, rq->curr);
>  		if (!next)
>  			break;

Suspend works perfectly with this patch. Thanks a lot and keep up the good 
work!
-- 
Regards,
Chris

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