Re: [PATCH] Skip vcpu_hotplug for VCPU 0 in smp_resume

[Brendan Cully <brendan@cs.ubc.ca>]

On Tuesday, 31 March 2009 at 09:53, Brendan Cully wrote:
> Skip vcpu_hotplug for VCPU 0 in smp_resume.
> This function can occasionally take up to 2 seconds to complete,
> and smp_suspend also skips VCPU 0.

I'm doing a bit of testing ahead of releasing Remus, and I've noticed
that there are a couple of places where resuming from suspension can
get stuck for a long time, which can cause Remus to think that the
domain has died. This is one of them.

The other is in the netfront accelerator. It tears down a xenstore
watch on the accelerator path at every suspend, and adds the watch
back on resume. As with any xenstore interaction, this can
occasionally take a very long time. I'm going from faulty memory here,
but I didn't think it was necessary to tear down and restore watches
across suspend. Would it make sense to move the watch remove and add
into the resume hook (taking it completely out of suspend and
suspend_cancel)?