Re: TSC not updating after resume: Bug or Feature?

[Fabio Comolli]

Hi Thomas.

On Sun, Dec 21, 2008 at 8:43 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Sun, 21 Dec 2008, Thomas Gleixner wrote:
>> On Thu, 18 Dec 2008, Rafael J. Wysocki wrote:
>> > >  5b7dba4: sched_clock: prevent scd->clock from moving backwards
>> > >
>> > > and the bug triggered by hibernation fixed instead.
>>
>> Hmm. Depending on the hibernation sleep time we can end up with a
>> pretty long delta between the pre suspend and the post resume call to
>> __update_sched_clock().
>>
>> I have the feeling that sched_clock looks into stale values after
>> resume and the first call to __update_sched_clock() trips over the
>> stale scd->clock value. Shaggy's patch brings scd->clock into the mix
>> and that might cause the whole machinery to blow up on resume.
>>
>> Also we need to investigate whether sched_clock is referencing gtod
>> values _before_ timekeeping is resume.
>
> I checked the two bugzillas (12149 & 12155) and both reporters have
> hpet=force on the command line.

Well, I'm the submitter of bug 12155 and I never had hpet=force on my
command line. I don't know where you found it.
Actually my command line is:

-------------------------------------------------------------------------------------------------------------------------
fcomolli@hawking:~> cat /proc/cmdline
root=/dev/sda2 resume=/dev/sda3 i8042.nomux=1 pciehp.pciehp_force=1
quiet splash=silent vga=791
-------------------------------------------------------------------------------------------------------------------------

By the way, I don't know if it matters but the problema happened with
in-kernel hibernation and also in out-of-tree TuxOnIce hibernation.
Maybe this can help debugging the issue, I don't know.

>
> One of the reporters said: "If I de-select CONFIG_HPET_TIMER then the
> issue went away ..."
>
> It looks like this was not further investigated. Is this problem
> reproducible on other systems as well ?
>
> Thanks,
>
>        tglx
> --

Regards,
Fabio


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