From: Keir Fraser <keir.fraser@eu.citrix.com>
Subject: Re: [Patch] continue_hypercall_on_cpu rework using
	tasklets
Date: Wed, 14 Apr 2010 07:46:56 +0100
Message-ID: <C7EB2370.1136B%keir.fraser@eu.citrix.com>
References: <4BC543F3.6080500@ts.fujitsu.com>
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On 14/04/2010 05:26, "Juergen Gross" <juergen.gross@ts.fujitsu.com> wrote:

>> Why do you change the interface of continue_hypercall_on_cpu()? What's a
>> 'hdl' anyway?
> 
> I need a way to find the migrate_info structure in case of nested calls of
> continue_hypercall_on_cpu(). Originally this was done by storing it in the
> vcpu structure, but this can't be done any more using tasklets. In my first
> attempt I saved it in the per-cpu area, but this approach isn't working if
> continue_hypercall_on_cpu() is called concurrently. So the cleanest way is
> to pass it via a parameter.

The per-cpu area method should work fine, since Xen is non-preemptive? I
don't think the concurrency you are concerned about can happen.

 -- Keir