linux-kernel - Re: s2disk hang update

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Date:	Tue, 16 Feb 2010 15:12:59 +0000
From:	Alan Jenkins <sourcejedi.lkml@...glemail.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Mel Gorman <mel@....ul.ie>, hugh.dickins@...cali.co.uk,
	Pavel Machek <pavel@....cz>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: s2disk hang update

On 2/16/10, Alan Jenkins <sourcejedi.lkml@...glemail.com> wrote:
> On 2/15/10, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> On Tuesday 09 February 2010, Alan Jenkins wrote:
>>> Perhaps I spoke too soon.  I see the same hang if I run too many
>>> applications.  The first hibernation fails with "not enough swap" as
>>> expected, but the second or third attempt hangs (with the same backtrace
>>> as before).
>>>
>>> The patch definitely helps though.  Without the patch, I see a hang the
>>> first time I try to hibernate with too many applications running.
>>
>> Well, I have an idea.
>>
>> Can you try to apply the appended patch in addition and see if that
>> helps?
>>
>> Rafael
>
> It doesn't seem to help.

To be clear: It doesn't stop the hang when I hibernate with too many
applications.

It does stop the same hang in a different case though.

1. boot with init=/bin/bash
2. run s2disk
3. cancel the s2disk
4. repeat steps 2&3

With the patch, I can run 10s of iterations, with no hang.
Without the patch, it soon hangs, (in disable_nonboot_cpus(), as always).

That's what happens on 2.6.33-rc7.  On 2.6.30, there is no problem.
On 2.6.31 and 2.6.32 I don't get a hang, but dmesg shows an allocation
failure after a couple of iterations ("kthreadd: page allocation
failure. order:1, mode:0xd0").  It looks like it might be the same
stop_machine thread allocation failure that causes the hang.

Regards
Alan

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