Re: [Xen-devel] [PATCH v2 2/2] xen: credit1: avoid boosting vCPUs being "just" migrated

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Fri, 2016-02-12 at 02:50 -0700, Jan Beulich wrote:
> > > > On 12.02.16 at 10:37, <dario.faggioli@xxxxxxxxxx> wrote:
> > @@ -787,6 +788,16 @@ _csched_cpu_pick(const struct scheduler *ops,
> > struct vcpu *vc, bool_t commit)
> > Âstatic int
> > Âcsched_cpu_pick(const struct scheduler *ops, struct vcpu *vc)
> > Â{
> > +ÂÂÂÂstruct csched_vcpu *svc = CSCHED_VCPU(vc);
> > +
> > +ÂÂÂÂ/*
> > +ÂÂÂÂÂ* We have been called by vcpu_migrate() (in schedule.c), as
> > part
> > +ÂÂÂÂÂ* of the process of seeing if vc can be migrated to another
> > pcpu.
> > +ÂÂÂÂÂ* We make a note about this in svc->flags so that later, in
> > +ÂÂÂÂÂ* csched_vcpu_wake() (still called from vcpu_migrate()) we
> > won't
> > +ÂÂÂÂÂ* get boosted, which we don't deserve as we are "only"
> > migrating.
> > +ÂÂÂÂÂ*/
> > +ÂÂÂÂset_bit(CSCHED_FLAG_VCPU_MIGRATING, &svc->flags);
> > ÂÂÂÂÂreturn _csched_cpu_pick(ops, vc, 1);
> > Â}
> 
> I think you either want __set_bit() here or ...
> 
Yes, this is completely serialized by the vcpu's scheduler lock, so I
indeed want __set_bit(), sorry for the overlook.

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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