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From: Christian Hesse <mail@earthworm.de>
To: Ingo Molnar <mingo@elte.hu>
Subject: Re: CFS and suspend2: hang in atomic copy
Date: Thu, 19 Apr 2007 22:32:51 +0200
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Cc: linux-kernel@vger.kernel.org,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Con Kolivas <kernel@kolivas.org>, Nick Piggin <npiggin@suse.de>,
       Mike Galbraith <efault@gmx.de>, Arjan van de Ven <arjan@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>, suspend2-devel@lists.suspend2.net
References: <20070413202100.GA9957@elte.hu> <200704190112.52838.mail@earthworm.de> <20070419062832.GD18894@elte.hu>
In-Reply-To: <20070419062832.GD18894@elte.hu>
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On Thursday 19 April 2007, Ingo Molnar wrote:
> * Christian Hesse <mail@earthworm.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
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- 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 =3D pick_next_task(rq, rq->curr);
>  		if (!next)
>  			break;

Suspend works perfectly with this patch. Thanks a lot and keep up the good=
=20
work!
=2D-=20
Regards,
Chris

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