linux-kernel - Re: Bisected: s2disk (uswsusp only) hangs just before poweroff

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Date:	Wed, 2 Dec 2009 10:35:38 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: Bisected: s2disk (uswsusp only) hangs just before poweroff

On Wed, Dec 02, 2009 at 08:57:05AM +0000, Alan Jenkins wrote:
> Mel Gorman wrote:
>> On Tue, Dec 01, 2009 at 07:59:40PM +0000, Alan Jenkins wrote:
>>   
>>> Hi
>>>
>>> Suspend to disk is (sometimes) hanging for me in 2.6.32-rc.  I 
>>> finally  got around to bisecting it, which blamed the following 
>>> commit by Mel:
>>>
>>> 5f8dcc2 "page-allocator: split per-cpu list into one-list-per-migrate-type"
>>>
>>> I was able to confirm this by reverting the commit, which fixed the   
>>> hang.  I had to revert one other commit first to avoid a conflict:
>>>
>>> a6f9edd "page-allocator: maintain rolling count of pages to free from 
>>>  the PCP"
>>>
>>>     
>>
>> Which RC kernel? Specifically, are the commits
>>
>> cc4a6851466039a8a688c843962a05689059ff3b always wake kswapd when restarting an allocation attempt
>> 9d0ed60fe9cd1fbf57f755cd27a23ae9114d7210 Do not allow interrupts to use ALLOC_HARDER
>>
>> applied?
>>
>> The latter one in particular might make a difference if s2disk is
>> pushing the system far below the watermarks. I don't suppose you know
>> where it's hanging? i.e. is it hanging in the allocator itself?
>>
>> If those patches are applied, then one difference that 5f8dcc2 makes is
>> that pages on the PCP lists but not of the right migratetype are not
>> used. Prior to that commit, an allocation might succeed even if the
>> buddy lists were empty because one of the other PCP page types would be
>> used.
>>
>>   
>>> -- detail --
>>>
>>> When I suspend my EeePc 701 to disk, it sometimes hangs after writing 
>>>  out the hibernation image.  The system is still able to resume from 
>>> this  image (after working around the hang by pressing the power 
>>> button). 
>>>
>>> This is specific to s2disk from the uswsusp package (which is now   
>>> installed by default on debian unstable).  It doesn't happen if I   
>>> uninstall uswsusp and use the in-kernel suspend instead.
>>>
>>>     
>>
>> This leads me to believe that uswsusp is able to push available pages
>> far below what is expected. It's a total guess though, I have no idea
>> how uswsusp is implemented or how it differs from what is in kernel.
>>
>>   
>>> The hang doesn't happen if I boot with "init=/bin/bash" and run 
>>> s2disk.   Nor does it happen if I boot normally, then switch to 
>>> single user mode  ("telinit 12").
>>>
>>> It only happens if I've logged in to KDE.  In the past, this has   
>>> indicated a problem in a network driver, since NetworkManager only 
>>> made  a connection once I logged in.  But it still hangs if I remove 
>>> both  ath5k and atl2 before I log into KDE.  (I actually tried 
>>> removing as  many modules as possible: atl2, ath5k, usbcore, 
>>> snd-hda-intel, psmouse,  pcspkr, battery, ac, themal, fan, and 
>>> eeepc-laptop).  Perhaps it's  something to do with the size of the 
>>> hibernation image.
>>>
>>>     
>>
>> I believe you are correct in that it's something to do with the size of
>> the hibernation image and how close to the edge the kernel gets pushed
>> as a result.
>>
>> Please confirm first that the two commits I mentioned above are in your
>> kernel. If not, would you mind trying the following patch?
>> Unfortunately, it's totally untested. The intention of the patch is to
>> use other PCP lists if the desired one cannot be refilled.
>>
>> Thanks.
>>   
>
> The hang happens on 2.6.32-rc8, which includes the two commits above.
>

Ok, that was somewhat expected as they only had an impact if there was a
storm of interrupts which was unlikely in this case. How about the
additional patch?

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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