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

Mel Gorman
2009-12-02T10:35:39Z

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