Re: [PATCH] xen: recalculate per-cpupool credits when updating timeslice

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

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On Tue, 2016-02-02 at 11:35 +0100, Juergen Gross wrote:
> On 02/02/16 10:53, Dario Faggioli wrote:
> > 
> > In any case, since the lack of locking and lack of recalculation
> > look
> > like two pretty independent existing bugs to me, can we have
> > either:
> >  a. two patches;
> >  b. one patch but with both the issues described in the changelog.
> > 
> > My preference going to a.
> 
> Without setting prv->credit the lock isn't necessary. In case of a
> race domain weights wouldn't be honored correctly for just one
> timeslice and I doubt this would be noticeable at all.
> 
Ah, yes, I see what you mean now!!

> OTOH I don't mind splitting the patch into two, I have to respin
> anyway.
> 
Well, no, given you explanation above, to which I agree (sory for not
seeing this before), keeping it being just one patch would actually be
better IMO...

But then, please, explain in the changelog that the recalculation would
introduce a race, and hence you also need to lock.

Thanks and regards,
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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