This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen

To: Christoph Egger <Christoph.Egger@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 11 Sep 2008 15:47:51 +0100
Cc: Haitao Shan <maillists.shan@xxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Shan, Haitao" <haitao.shan@xxxxxxxxx>
Delivery-date: Thu, 11 Sep 2008 07:48:19 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <C4EEEA80.27082%keir.fraser@xxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AckUGzATbsSqPIAOEd2NXQAX8io7RQAAi1PP
Thread-topic: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen
User-agent: Microsoft-Entourage/
On 11/9/08 15:32, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>>> I note that the VCPU currently running on the offlined CPU continues to run
>>> there even after __cpu_disable(), and until that CPU does a final run
>>> through the scheduler soon after. I hope it does not matter there is one
>>> vcpu with v->processor == offlined_cpu for a short while
>> This is not acceptable regarding to machine check. When Dom0 offlines a
>> defect cpu, nothing may continue on it or silent data corruption occurs.
> It doesn't run for unbounded time. The offline CPU will immediately run
> softirq work as the very next thing it does, causing a run through the
> scheduler, where it will 100% definitely pick up the idle vcpu and hence
> play dead in the idle loop.
> This won't be guaranteed synchronous with a offline request via a hypercall
> though. By which I mean, that hypercall may return but the last vcpu may not
> stop running on the cpu until some tiny amount of time later.

Actually I'm wrong on this. __cpu_die() will ensure the CPU really is
totally offline before returning. So calls to cpu_down() really are
synchronous already.

 -- Keir

Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>