linux-kernel - Re: 2.6.25.9: system clocks works normally then speeds up 4x...

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Date:	09 Jul 2008 13:01:31 -0700
From:	Philippe Troin <phil@...i.org>
To:	"john stultz" <johnstul@...ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.25.9: system clocks works normally then speeds up 4x...

"john stultz" <johnstul@...ibm.com> writes:

> On Wed, Jul 9, 2008 at 12:21 PM, Philippe Troin <phil@...i.org> wrote:
> >
> > Symptoms:
> >
> >  The system boots fine. Clock seems to run normally.
> >
> >  Then after a random amount of time (on the current boot, 3 days),
> >  clock starts to be running 2-4x faster (on the current boot, 4x).
> >
> >  I have tried booting with "nohz=off highres=off" but it does not
> >  help.
> 
> Could you provide the output from the following:
>    sudo cat /sys/devices/system/clocksource/clocksource0/*

Sure.

It is:
available: jiffies tsc 
current:   jiffies

> Did this issue occur with 2.6.24 or earlier kernels?

No.  It started with 2.6.25.

Interestingly:

  I've just modified the current clocksource to tsc and the clock went
  back to its normal speed.

  Then I reset the current clocksource to jiffies, and the clock went
  back to its (wrong) 4x speed.

So it looks like the kernel is counting jiffies 4x too fast.

Phil.
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