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

Alan Jenkins
2009-12-02T08:57:07Z

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.

Thanks!
Alan