[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Re: [PATCH 1/4] CPU online/offline support in Xen
On 10/9/08 11:43, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote: > I feel this is more complicated than it needs to be. > > How about clearing VCPUs from the offlined CPU's runqueue from the very end > of __cpu_disable()? At that point all other CPUs are safely in softirq > context with IRQs disabled, and we are running on the correct CPU (being > offlined). We could have a hook into the scheduler subsystem at that point > to break affinities, assign to different runqueues, etc. We would just need > to be careful not to try an IPI. :-) This approach would not need a > cpu_schedule_map (which is really increasing code fragility imo, by creating > possible extra confusion about which cpumask is the wright one to use in a > given situation). > > My feeling, unless I've missed something, is that this would make the patch > quite a bit smaller and with a smaller spread of code changes. Another thought: we may (appear to) need an IPI after VCPUs have been migrated to other runqueues. And actually that will be safe because smp_send_event_check_cpu() is non-blocking (does not wait for the remote CPU to run the IPI handler). So it *is* safe to do non-blocking IPIs from stop_machine_run() context. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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