RE: [Xen-devel] Clock jumped 50 minutes in dom0 caused incorrect 2008 R2 domU time

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> > Unfortunately these kinds of time problems can be notoriously hard to
> > pin down and diagnose.
> 
> This seems to occur when one -- or possibly all -- vcpus
> are "spinning" for an unexpectedly long period of time.  If so
> it may be possible to synthesize some kind of long-but-non-infinite
> deadlock in a domU kernel which might reproduce the problem.

Saw this on LKML:
http://lkml.org/lkml/2010/10/27/366 

The solution refers to a recent git commit so is unlikely to
be the specific cause for the problem we've seen.  But the
analysis sounds very familiar and also corresponds to my
observation above:  In short, SOMEthing (in the guest kernel
or in Xen) is causing the guest to "go out to lunch" for some
extended period of time, which confuses the watchdog timer,
which disables TSC as a clocksource.

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