Re: Clocksource tsc unstable (delta = -8589361717 ns) in current git

john stultz
2010-10-26T19:21:48Z

On Tue, 2010-10-26 at 17:48 +0200, Thomas Gleixner wrote:
> On Tue, 26 Oct 2010, Markus Trippelsdorf wrote:
> > On Tue, Oct 26, 2010 at 03:18:43PM +0200, Borislav Petkov wrote:
> > > otherwise, I don't see anything strange in your dmesg. Unless tglx has a
> > > better idea, I'd ask you to bisect it. 5618 changesets shouldn't be that
> > > much but I don't know, if the issue appears every several hours it could
> > > still be tedious.
> >
> > That would be a several week long process, as the issue appears ~ every
> > 2 days here on this machine running 24/7.
>
> There is only a single commit in that area post 2.6.36:
>
> 8af3c153baf95374eff20a37f00c59a295b52756
>
> But I have a hard time how this should make this happen. John ?

Yea, that one doesn't look connected to me.

There have been a few cases that I've seen where we can get false
positives for bad TSCs due to the watchdog clocksource having problems
(or the clocksource watchdog thread getting delayed for such a long time
the watchdog clocksource wraps and we then can't validly compare the two
- although this would be hard to trigger with non-rt kernels).

>From your dmesg, I'd guess the hpet is the watchdog clocksource, so I'd
be on the lookout for hpet related changes.

Maybe does reverting 995bd3bb5c78f3ff71339803c0b8337ed36d64fb hide the
issue?

thanks
-john