Re: [Xen-devel] xl shutdown --wait "racy"

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-04-16 at 16:26 +0200, Sander Eikelenboom wrote:
> Wednesday, April 16, 2014, 4:13:59 PM, you wrote:
> 
> > On Wed, 2014-04-16 at 16:08 +0200, Sander Eikelenboom wrote:
> >> Hi Ian (C|J) Konrad,
> >> 
> >> I'm currently trying to workaround the pci-(detach|assignable-remove) 
> >> issues i 
> >> reported earlier. 
> >> 
> >> The workaround i thought of was:
> >> - shutting down the guest
> >> - starting it without 1 of the original devices passed through
> >> - use xl pci-assignable-remove and bind the device to the dom0 driver.
> >> 
> >> But during this i noticed that a "xl shutdown --wait" does wait .. but 
> >> returns:
> >> - Before the domain is removed from for instance "xl list", it still 
> >> listed there in 
> >> "--ps--" state.
> >> - before pciback has done it's restore config space magic.
> >> 
> >> So it seems the wait loop is exiting somewhat prematurely, is this 
> >> expected ? 
> 
> > It is waiting for the domain to be shutdown (state 's') not for the
> > domain to be destroyed. So it's doing what it said it would (I
> > appreciate you might not find this distinction helpful under the
> > circumstances...)
> 
> It's at least not entirely what i expected ;-)
> 
> Is it because there can be different "follow-up actions" due to the 
> "on_poweroff=" config option ?

Not really, those are somewhat unrelated.

shutdown and destroy are two distinct events. Once a domain has shutdown
(called the shutdown hypercall etc) it goes into state "shutdown" and an
event is generated from the hypervisor to the toolstack. The toolstack's
response to this is to actually destroy the domain, that is to tear down
the resources it is using etc.

on_* only matter for the destroy phase since they tell the toolstack
what it should do (restart, preserve, really destroy etc).

> I can see the shutdown state would be the thing to wait for if it's 
> configured 
> with "preserve", but if it's configured with the default "destroy" i would 
> expect it to wait until the guest is actually destroyed. The "restart" is 
> perhaps 
> somewhat more difficult, same goes for the coredump variants.


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