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.
