linux-kernel - Re: Kernel NFS lockd freezes notebook on shutdown (Linux 2.6.22-rc1 + CFS v12)

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Message-ID: <20070518202805.GA298@tv-sign.ru>
Date:	Sat, 19 May 2007 00:28:05 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Zilvinas Valinskas <zilvinas@...ibox.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: Kernel NFS lockd freezes notebook on shutdown (Linux 2.6.22-rc1 + CFS v12)

On 05/18, Zilvinas Valinskas wrote:
>
> On Thu, 2007-05-17 at 22:45 +0400, Oleg Nesterov wrote:
> >
> > However, I can't understand why cleanup_workqueue_thread() hangs anyway.
> > It shouldn't. Looks like rpciod/1 was preempted, and can't get CPU. According
> > to kernel-nfs-freeze.log it is TASK_RUNNING. Strange.
> >
> > It is very sad, because this code was supposed to be cleanuped anyway,
> > but if it is really buggy, it would be great to know why.
>
> Can this be related to :
>
> CONFIG_PREEMPT=y

Yes, but this preemption should be very unlikely, but it happens every time
for you, strange. lockd in turn spins with preemption enabled, but somehow
rpciod/1 can't make progress. system_state == SYSTEM_HALT, but this shouldn't
affect preempt_schedule_irq(). So I think there is something else.

> workqueue.objdump - without any patch.

So it hangs waiting for cwq->thread == NULL, as expected.

OK. I still can't see how this code could be wrong, but it is bad anyway and
should be changed. The 2nd patch was done more than a month ago, but was
delayed for some stupid reasons. I'll send it today.

Still, it is not clear to me what happens, and you have other crashes with
nfs stop/start

	http://marc.info/?l=linux-kernel&m=117939027602591
	http://marc.info/?l=linux-kernel&m=117939257630947

which probaly need some attention.

Thanks!

Oleg.

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