Re: [Xen-devel] [PATCH] Fix softlockup issue after vcpu hotplug

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 30/1/07 12:45 pm, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> Actually I'm a bit interested in this case, where watchdog thread
> depends on timer interrupt to be awaken, while next timer interval
> depends on soft timer wheel. For the new online cpu, all its
> processes previously running have been migrated to others before
> offline. Thus when just coming back online, there may be no
> meaningful timer wheel and few activities on that vcpu. In this case,
> a (LONG_MAX >> 1) may be returned as a big timeout.

Yeah, but the thread should get migrated back again (or recreated) in fairly
short order. I think we can agree it should take rather less than 10
seconds. :-)

> So saying this new watchdog model, simply walking timer wheel is
> not enough. Maybe we can force max timeout value to 1s in safe_halt
> to special this case? I'll make a try on this. But this will make current
> tick-less model to a bit tick-ful back. :-)

I'm sure this will fix the issue. But who knows what real underlying issue
it might be hiding?

 -- Keir



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