Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH 38/51] intel-idle: Fix CPU hotplug callback registration | Date | Thu, 06 Feb 2014 13:43:08 +0100 |
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On Thursday, February 06, 2014 03:41:23 AM Srivatsa S. Bhat wrote: > Subsystems that want to register CPU hotplug callbacks, as well as perform > initialization for the CPUs that are already online, often do it as shown > below: > > get_online_cpus(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > register_cpu_notifier(&foobar_cpu_notifier); > > put_online_cpus(); > > This is wrong, since it is prone to ABBA deadlocks involving the > cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently > with CPU hotplug operations). > > Instead, the correct and race-free way of performing the callback > registration is: > > cpu_maps_update_begin(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > /* Note the use of the double underscored version of the API */ > __register_cpu_notifier(&foobar_cpu_notifier); > > cpu_maps_update_done(); > > > Fix the intel-idle code by using this latter form of callback registration. > > Cc: Len Brown <lenb@kernel.org> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > Cc: linux-pm@vger.kernel.org > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
This looks good to me. Len, what do you think?
Srivatsa, how does it depend on the rest of your series?
> --- > > drivers/idle/intel_idle.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c > index 8e1939f..716ee5a 100644 > --- a/drivers/idle/intel_idle.c > +++ b/drivers/idle/intel_idle.c > @@ -681,14 +681,19 @@ static int __init intel_idle_init(void) > if (intel_idle_cpuidle_devices == NULL) > return -ENOMEM; > > + cpu_maps_update_begin(); > + > for_each_online_cpu(i) { > retval = intel_idle_cpu_init(i); > if (retval) { > + cpu_maps_update_done(); > cpuidle_unregister_driver(&intel_idle_driver); > return retval; > } > } > - register_cpu_notifier(&cpu_hotplug_notifier); > + __register_cpu_notifier(&cpu_hotplug_notifier); > + > + cpu_maps_update_done(); > > return 0; > } > @@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void) > intel_idle_cpuidle_devices_uninit(); > cpuidle_unregister_driver(&intel_idle_driver); > > + cpu_maps_update_begin(); > > if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) > on_each_cpu(__setup_broadcast_timer, (void *)false, 1); > - unregister_cpu_notifier(&cpu_hotplug_notifier); > + __unregister_cpu_notifier(&cpu_hotplug_notifier); > + > + cpu_maps_update_done(); > > return; > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
-- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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