[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [Patch] continue_hypercall_on_cpu rework using tasklets


  • To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
  • Date: Wed, 14 Apr 2010 08:58:26 +0200
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 14 Apr 2010 00:00:06 -0700
  • Domainkey-signature: s=s1536a; d=ts.fujitsu.com; c=nofws; q=dns; h=X-SBRSScore:X-IronPort-AV:Received:X-IronPort-AV: Received:Received:Message-ID:Date:From:Organization: User-Agent:MIME-Version:To:CC:Subject:References: In-Reply-To:X-Enigmail-Version:Content-Type: Content-Transfer-Encoding; b=p5Of6B6nlMLqEtyzPfTTPC3CePetCnzhZ4YAKd5Ykj39F3gInaQQUPq5 kfRKUnbrKRId3/mUBJka/jssQxMjkgipSVAIFA6p/E6VctVl3S0YniIzD sVCFDrEFsJgvjqCohQ7PngEvQGUuuzudwlC7k2y2D0yzvTr3mXITWOLEt W/FL7kp+EIK/fCLYdJhECgF51KTZP73UkpoBbS3+IUyjlI6yWRzCdkxCY crOwgi1/mPyNK1W9/dbZpFheOWXdo;
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Keir Fraser wrote:
> On 14/04/2010 05:26, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> 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.

The tasklet knows only on which cpu it is running, so the data has to be
stored on the target cpu. And one pcpu can be the target of concurrent calls
from different calling cpus...


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.