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

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Skip vcpu_hotplug for VCPU 0 in smp_resume
From: Kieran Mansley <kmansley@xxxxxxxxxxxxxx>
Date: Thu, 02 Apr 2009 10:13:41 +0100
Cc: "andy@xxxxxxxxx" <andy@xxxxxxxxx>, Brendan Cully <brendan@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On Thu, 2009-04-02 at 09:27 +0100, Keir Fraser wrote:
> On 02/04/2009 09:13, "Kieran Mansley" <kmansley@xxxxxxxxxxxxxx> wrote:
> > On Wed, 2009-04-01 at 11:39 -0700, Brendan Cully wrote:
> >> I'm afraid my memory of the kernel suspend mechanics has gotten a bit
> >> rusty over the last few months, so I may be off-base here. But I
> >> thought that xs_suspend masked watches until xs_reusume or
> >> xs_suspend_cancel? If that is the case, isn't that on its own enough
> >> to protect netfront?
> > 
> > If that's the case, it should be enough, yes.
> > 
> > Do watches that would have fired during that time fire at the end of
> > masked period?  If not, we'd still have to access xenstore on suspend
> > cancel to check if we've missed a change.
> I don't think watches get lost across suspend-cancel, just delayed.

OK, I'll try and produce a patch based on the assumptions that (i)
watches won't fire between suspend and either resume or suspend-cancel;
(ii) any that would have fired are triggered after a suspend-cancel; and
(iii) the watch must be refreshed on a resume (with no guarantees about
lost watches).


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