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Re: [Xen-devel] domain pause vs. watchdog timer

To: Laszlo Ersek <lersek@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
Subject: Re: [Xen-devel] domain pause vs. watchdog timer
From: Keir Fraser <keir@xxxxxxx>
Date: Thu, 13 Oct 2011 15:56:33 +0100
Cc: Igor Mammedov <imammedo@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] domain pause vs. watchdog timer
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On 13/10/2011 15:38, "Laszlo Ersek" <lersek@xxxxxxxxxx> wrote:

> On 10/13/11 16:21, Jan Beulich wrote:
>>>>> On 13.10.11 at 15:41, Laszlo Ersek<lersek@xxxxxxxxxx>  wrote:
>>> if a domain is paused (= not scheduled), its process that keeps
>>> otherwise kicking /dev/watchdog and (thusly the hypervisor) "freezes"
>>> too. Should pausing a domain suspend (or "inactivate") its watchdog_timers?
>> 
>> I would say yes it should. And you say it doesn't?
> 
> I must have missed a changeset (or a hunk?) related to pausing:
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=742880#c1
> 
> I backported 21529 from xen-unstable to the RHEL-5 hypervisor version,
> and Igor tested pausing a Fedora 16 HVM guest. The domU was destroyed
> while it was paused.

You are just as likely to upset a watchdog implemented entirely internally
to the guest, and which we have no chance to disable/suspend when a domain
is paused. Domain pausing from the dom0 command line really doesn't have a
production use case afaik -- just don't do it is my helpful suggestion.

 -- Keir



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