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SubjectRe: Clock incorrect on 2.6.31-rc2
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On Thu, 2009-07-09 at 15:38 -0700, Stephen Hemminger wrote:
> On Thu, 9 Jul 2009 14:58:37 -0700
> john stultz <johnstul@us.ibm.com> wrote:
>
> > On Thu, Jul 9, 2009 at 2:10 PM, Stephen Hemminger<shemminger@vyatta.com> wrote:
> > > My system (desktop Ubuntu 9.0) runs fine with 2.6.30, but with 2.6.31-rc2 it does
> > > not keep time correctly. Also ntptime reports an error.
> >
> > Can you better describe how it does not keep time? Is time moving too
> > slow? too fast?
>
> The clock just seemed to stop, or be wildly stuck in past.

Hrmm. And the box continues to function? If the clock stops, so does
timers, which will usually make a box seem to be totally hung.

>From the messages below, it doesn't seem to be stopped.

> > Could you include output from the following commands with 2.6.31-rc2
> > (and 2.6.30 if you have the time).
> > $ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> > $ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> > $ dmesg
> > $ ntpdc -c peers
> > $ ntpdc -c kerninfo
>
> $ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> tsc hpet acpi_pm
> $ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> tsc


Ok. One thing to check is if the issue goes away if you either boot with
"clocksource=acpi_pm" or run

echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
> # ntpdc -c peers
> remote local st poll reach delay offset disp
> =======================================================================
> *ussprometheus.r 192.168.1.3 2 128 377 0.09094 0.007730 0.06786

You don't seem to be very far off right now. Only 7ms. And it seems you
have gone into NTP sync state (the * denotes that).

I'm guessing ntptime no longer gives you errors now?

> # ntpdc -c kerninfo
> pll offset: 0.005107 s
> pll frequency: 155.028 ppm
> maximum error: 0.219122 s
> estimated error: 0.007209 s
> status: 0001 pll
> pll time constant: 7
> precision: 1e-06 s
> frequency tolerance: 500 ppm

This all looks normal.



> $ dmesg
> [ 0.000000] Linux version 2.6.31-rc2 (shemminger@nehalam) (gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) ) #149 SMP Tue Jul 7 18:22:50 PDT 2009
[snip]
> [ 0.000000] Fast TSC calibration using PIT
> [ 0.000000] Detected 2673.143 MHz processor.

You might watch from boot to boot if the above MHz is varying by too
much.

Everything else looks ok.


I'm a little stumped. Does the problem occur on every reboot? How long
does the box need to be up before you see an issue? Or does it go away
after a little while?

thanks
-john




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