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SubjectRe: Regression in gdm-2.18 since 2.6.24
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On Tue, 2008-04-08 at 14:20 +0530, Srivatsa Vaddagiri wrote:
> On Mon, Apr 07, 2008 at 12:48:33AM +0100, Ken Moffat wrote:
> > Well, I found your analysis convincing. Unfortunately, my hardware
> > disagreed. Testing -rc8 with CONFIG_GROUP_SCHED disabled (a test is
> > a mixture of 5 attempts to restart and 5 to shutdown):
> >
> > 1. the base version success is 4/10
> >
> > 2. increasing the granularity by a factor of 10 as you requested,
> > success is 8/10
>
> This makes me think that we are just exposing a timing related problem
> in gdm here.
>
> How abt a larger factor?
>
> # echo 200000000 > /proc/sys/kernel/sched_wakeup_granularity_ns
>
> Does that make it 10/10 ?!
>
> Anyway, it would be interesting to analyze the failure scenario more
> (with help from gdm developers). Can you get some more debug data in this
> regard?
>
> Before you shutdown,
>
> # strace -p <gdm-binary-pid1> 2>/tmp/gdmlog1 &
> # strace -p <gdm-binary-pid2> 2>/tmp/gdmlog2 &
>
> Now shutdown and wait few minutes to confirm its not working. Send me
> the strace log files ..Hopefully this will give a hint on what they are
> deadlocked on (in the last log you sent, i can see both gdm-binaries in
> sleep state ..whether that was a momentary state or whether they are
> actually deadlocked, will be confirmed by strace logs above).
>
> > If I was confused earlier, I guess I must be dazed and confused
> > now!
>
> me too!
>
> Ingo/Peter, Any other suggestions you have?

Sounds like a race condition to me; non of these changes affect
correctness in a strict manner of speaking.





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