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Re: [Xen-devel] [PATCH 0 of 3] Remus: control tool

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0 of 3] Remus: control tool
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 02 Dec 2009 10:17:50 -0800
Cc: "andy@xxxxxxxxx" <andy@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "konrad.wilk@xxxxxxxxxx" <konrad.wilk@xxxxxxxxxx>
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On 12/02/09 00:07, Keir Fraser wrote:
> The issue in 2.6.18 was that, if doing back-to-back save/restores, the next
> event-channel notification could come in before domU was finished with
> previous s/r cycle, and then the notification got dropped. There are a
> number of ways of dealing with that of course: I implemented a little state
> machine; or you could probably do it with some kind of ticket-based scheme;
> or perhaps have the evtchn irq handler spawn a kthread which blocks on the
> mutex (I liked that one least as it needs to allocate resources).

Hm, my first thought is "why does that matter?".  But I guess the
host/guest save protocol is fairly brittle, and if the guest doesn't
respond to a particular save it will get wedged.  But then, should the
control stack be sending back to back save requests?  Shouldn't it wait
until the previous save has finished?


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