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SubjectRe: [PATCH] locking/osq: Drop the overload of osq lock
On Sat, Jun 25, 2016 at 09:20:25PM +0200, Peter Zijlstra wrote:
> On Sun, Jun 26, 2016 at 01:27:56AM +0800, panxinhui wrote:
> > >> Would that not have issues where the owner cpu is kept running but the
> > >> spinner (ie. _this_ vcpu) gets preempted? I would think that in that
> > >> case we too want to stop spinning.
> > >>
> > >
> > do you mean that the spinner detect itself had yield out during the
> > big spin loop?
> >
> > It is very possible to happen. BUT if spinner(on this vcpu) yield
> > out, the next spinner would break the spin loop. AND if spinner
> > detect itself yield out once, it’s very possible to get the osq lock
> > soon as long as the ower vcpu is running.
> >
> > SO I think we need just check the owner vcpu’s yield_count.
>
> I had a quick look at KVM and it looks like it only has
> kvm_cpu::preempted, which would suggest the interface boqun proposed.
>
> We'll have to look at many of the other virt platforms as well to see
> what they can do.
>
> We could also provide _both_ interfaces and a platform can implement
> whichever variant (or both) it can.
>

Make sense ;-)

Lemme cook something for further discussions.

Regards,
Boqun
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