Re: [PATCH v2 3/6] xen: sched: clarify use cases of schedule_cpu_switch()

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Fri, 2015-10-23 at 15:42 +0200, Juergen Gross wrote:
> On 10/21/2015 07:10 PM, Dario Faggioli wrote:

> > Also, all the operations done in schedule_cpu_switch() itself,
> > depend
> > either on per_cpu(scheduler) or on per_cpu(schedule_data) being
> > updated
> > properly, rather than on per_cpu(cpupool) (including the locking
> > that
> > you are mentioning above).
> > 
> > What am I missing?
> 
> Hmm, good question. I'm rather sure I had a problem related to
> exactly
> this topic in the early days of cpupools. Maybe the critical code has
> been modified since then. Or my memory is wrong. 
>
From a quick archeological investigation, some things certainly have
changed. Still, I can't spot anything directly related to this, but
it's quite possible that it's there and I'm missing it.

> Or we both don't see
> it now. ;-)
> 
Yep! :-)

> In case there is a problem it should show up doing a test which
> concurrently does all of the following:
> 
> - move a domain between two cpupools
> - move a cpu between the two cpupools
> - create and destroy a domain in one of the two cpupools
> 
Ok, I'll arrange for this and report.

> If the system is surviving this test for a couple of hours you are
> fine
> and then for the attached patch:
> 
> Acked-by: Juergen Gross <jgross@suse.com>
> 
Thanks :-)
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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