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SubjectRe: [PATCH v2] keep rd->online and cpu_online_map in sync
On Mon, Mar 10, 2008 at 06:34:56PM -0700, Suresh Siddha wrote:
> On Mon, Mar 10, 2008 at 04:36:13PM -0700, Andrew Morton wrote:
> > > --- a/kernel/sched.c
> > > +++ b/kernel/sched.c
> > > @@ -5881,7 +5881,8 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
> > > spin_unlock_irq(&rq->lock);
> > > break;
> > >
> > > - case CPU_DOWN_PREPARE:
> > > + case CPU_DYING:
> > > + case CPU_DYING_FROZEN:
> > > /* Update our root-domain */
> > > rq = cpu_rq(cpu);
> > > spin_lock_irqsave(&rq->lock, flags);
> >
> > Does this make
> > cpu-hotplug-register-update_sched_domains-notifier-with-higher-prio.patch
> > (below) obsolete,
>
> Yes. I would like to Ack for the
> keep-rd-online-and-cpu_online_map-in-sync.patch, as it is more cleaner.
>
>
> > or do we want both?
>
> No. I don't think so. Gautham, do you agree?

Yup I agree! Greg's patch is better since i clears the
bit *just* before we take the cpu down. That way we won't mess with the
ordering.

But I would still prefer that we update the sched_domains early on
after cpu-hotplug rather than doing it after the subsystems have run
their notifiers.

Will send a seperate patch for that one.
>
> thanks,
> suresh
>
> >
> > --- a/kernel/sched.c~cpu-hotplug-register-update_sched_domains-notifier-with-higher-prio
> > +++ a/kernel/sched.c
> > @@ -7096,8 +7096,16 @@ void __init sched_init_smp(void)
> > if (cpus_empty(non_isolated_cpus))
> > cpu_set(smp_processor_id(), non_isolated_cpus);
> > put_online_cpus();
> > - /* XXX: Theoretical race here - CPU may be hotplugged now */
> > - hotcpu_notifier(update_sched_domains, 0);
> > + /*
> > + * XXX: Theoretical race here - CPU may be hotplugged now
> > + *
> > + * We register the notifier with priority 11, which means that
> > + * update_sched_domains() will be called just before migration_call().
> > + *
> > + * This is necessary to ensure that the rt wake up logic works fine
> > + * and the rq->rd->online_map remains in sync with the cpu_online_map.
> > + */
> > + hotcpu_notifier(update_sched_domains, 11);
> >
> > /* Move init over to a non-isolated CPU */
> > if (set_cpus_allowed(current, non_isolated_cpus) < 0)
> > _
> >

--
Thanks and Regards
gautham


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