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

Alan Jenkins
2009-12-02T11:35:04Z

Mel Gorman wrote:
> 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?
>

The patch doesn't help. I still see the same hang (and the hung task
backtraces look the same as before).

Thanks
Alan