On 28/05/18 21:24, Waiman Long wrote: > On 05/28/2018 09:12 PM, Waiman Long wrote: > > On 05/24/2018 06:28 AM, Juri Lelli wrote: > >> On 17/05/18 16:55, Waiman Long wrote: > >> > >> [...] > >> > >>> @@ -849,7 +860,12 @@ static void rebuild_sched_domains_locked(void) > >>> * passing doms with offlined cpu to partition_sched_domains(). > >>> * Anyways, hotplug work item will rebuild sched domains. > >>> */ > >>> - if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask)) > >>> + if (!top_cpuset.isolation_count && > >>> + !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask)) > >>> + goto out; > >>> + > >>> + if (top_cpuset.isolation_count && > >>> + !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask)) > >>> goto out; > >> Do we cover the case in which hotplug removed one of the isolated cpus > >> from cpu_active_mask? > > Yes, you are right. That is the remnant of my original patch that allows > > only one isolated_cpus at root. Thanks for spotting that. > > I am sorry. I would like to take it back my previous comment. The code > above looks for inconsistency in the state of the effective_cpus mask to > find out if it is racing with a hotplug event. If it is, we can skip the > domain generation as the hotplug event will do that too. The checks are > still valid with the current patchset. So I don't think we need to make > any change here.
Yes, these checks are valid, but don't we also need to check for hotplug races w.r.t. isolated CPUs (of some other sub domain)?
