From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [PATCH] sched: fix race between sched_move_domain()
 and vcpu_wake()
Date: Fri, 11 Oct 2013 12:47:15 +0100
Message-ID: <CE7DA3D3.39085%keir.xen@gmail.com>
References: <1381426196-11392-1-git-send-email-david.vrabel@citrix.com>
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To: David Vrabel <david.vrabel@citrix.com>, xen-devel@lists.xen.org
Cc: George Dunlap <george.dunlap@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Juergen Gross <juergen.gross@ts.fujitsu.com>
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On 10/10/2013 18:29, "David Vrabel" <david.vrabel@citrix.com> wrote:

> From: David Vrabel <david.vrabel@citrix.com>
> 
> sched_move_domain() changes v->processor for all the domain's VCPUs.
> If another domain, softirq etc. triggers a simultaneous call to
> vcpu_wake() (e.g., by setting an event channel as pending), then
> vcpu_wake() may lock one schedule lock and try to unlock another.
> 
> vcpu_schedule_lock() attempts to handle this but only does so for the
> window between reading the schedule_lock from the per-CPU data and the
> spin_lock() call.  This does not help with sched_move_domain()
> changing v->processor between the calls to vcpu_schedule_lock() and
> vcpu_schedule_unlock().
> 
> Fix the race by taking the schedule_lock for v->processor in
> sched_move_domain().
> 
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Cc: George Dunlap <george.dunlap@eu.citrix.com>
> Cc: Juergen Gross <juergen.gross@ts.fujitsu.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Keir Fraser <keir@xen.org>