Messages in this thread |  | | Date | Mon, 10 Mar 2008 15:25:56 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] cpu-hotplug: Register update_sched_domains() notifier with higher prio |
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On Mon, 10 Mar 2008 18:43:55 +0530 Gautham R Shenoy <ego@in.ibm.com> wrote:
> cpu-hotplug: Register update_sched_domains() notifier with higher prio > From: Gautham R Shenoy <ego@in.ibm.com> > > The current -rt wake_up logic uses the rq->rd->online_map which is > updated on cpu-hotplug events by update_sched_domains(). Currently > update_sched_domains() is registered with a priority 0. It is > preferable that update_sched_domains() be the first notifier called on > a CPU_DEAD or CPU_ONLINE events inorder to ensure that the > rq->rd->online_map is in sync with the cpu_online_map. > > This way on a CPU_DOWN_PREPARE, > we would destroy the sched_domains and reattach all the rq's to the > def_root_domain. This will be followed by a CPU_DOWN_PREPARE in > migration_call() which will clear the bit of the cpu going offline > from the corresponding rq. > This will ensure that no task will be woken up on the cpu which is > going to be offlined between CPU_DOWN_PREPARE and CPU_DEAD. > > Ditto for the CPU_ONLINE path. > > Tested on a 4-way Intel Xeon Box with cpu-hotplug tests running in parallel > with kernbench. > > Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> > --- > > kernel/sched.c | 12 ++++++++++-- > 1 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 69ecb1a..374c46f 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -7079,8 +7079,16 @@ 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)
This fixes my poweroff-doesn't-work post-2.6.24 regression.
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