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 <l...@kernel.org>
> Cc: "Rafael J. Wysocki" <r...@rjwysocki.net>
> Cc: linux...@vger.kernel.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@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 majord...@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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
