On Thu, Sep 05, 2019 at 06:37:56PM -0400, Daniel Jordan wrote: > On Thu, Sep 05, 2019 at 02:17:35PM +1000, Herbert Xu wrote: > > I don't think waiting is an option. In a pathological case the > > hardware may not return at all. We cannot and should not hold off > > CPU hotplug for an arbitrary amount of time when the event we are > > waiting for isn't even occuring on that CPU. > > Ok, I hadn't considered hardware not returning. > > > I don't think flushing is needed at all. All we need to do is > > maintain consistency before and after the CPU hotplug event. > > I could imagine not flushing would work for replacing a pd. The old pd could > be freed by whatever drops the last reference and the new pd could be > installed, all without flushing. > > In the case of freeing an instance, though, padata needs to wait for all the > jobs to complete so they don't use the instance's data after it's been freed. > Holding the CPU hotplug lock isn't necessary for this, though, so I think we're > ok to wait here. [FYI, I'm currently on leave until mid-October and will return to this series then.]
