Re: [Xen-devel] Re: [PATCH] [RFC] Fix a small window on CPU onli

To:	"Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Subject:	Re: [Xen-devel] Re: [PATCH] [RFC] Fix a small window on CPU online/offline
From:	Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date:	Fri, 02 Apr 2010 08:27:57 +0100
Cc:	"Tian, Kevin" <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
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On 02/04/2010 08:14, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> Hm, actually maybe that could work. You might not even need a flag in case
> current is non-idle in cpu_disable_scheduler(). It might suffice to force
> context_switch() to do full context switch synchronously when the CPU is
> going offline (see appended patch). I was thinking there was a race as soon
> as the cpu is cleared from cpu_online_map, but actually the problem occurs
> only once the vcpu is descheduled, so if we can synchronously sync its state
> before calling context_saved(), perhaps we are fine.
> 
> This could be a very small patch after all! :-)

Perhaps even as small as the attached patch?

It's simple enough we could almost consider it for 4.0.0.

 -- Keir

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Re: [Xen-devel] Re: [PATCH] [RFC] Fix a small window on CPU online/offli