Commit 852d8cb1 authored Jul 03, 2012 by Deepthi Dharwar Committed by Benjamin Herrenschmidt Jul 11, 2012

powerpc/cpuidle: Fixes for pseries_idle hotplug notifier

Currently the call to pseries_notify_cpuidle_add_cpu(), that takes
action on the cpuidle front when a cpu is added/removed
is being made from smp_xics_setup_cpu().
This caused lockdep issues as
reported https://lkml.org/lkml/2012/5/17/2

On addition of each cpu,
resources were cleared and re-allocated each time, all in critical
section as part of start_secondary() call were interrupts are disabled.
To resolve this issue, the pseries_notify_cpuidle_add_cpu() call is
is being replaced by a hotplug notifier which
would prevent cpuidle resources from being
released and allocated each time cpu is onlined in the critical code path.
It was fixed in https://lkml.org/lkml/2012/5/18/174

.

Also it is essential to call cpuidle_enable/disable_device
between  cpuidle_pause_and_lock()  and
cpuidle_resume_and_unlock()  when used externally
to avoid race conditions. Add support for CPU_ONLINE_FROZEN
and CPU_DEAD_FROZEN as part of hotplug notify event for
pseries_idle  and unregister hotplug notifier
while exiting out. The above mentioned issues
are fixed as part of this patch.

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent 8bf8385b

arch/powerpc/platforms/pseries/processor_idle.c

+18 −5

Original line number	Diff line number	Diff line
		@@ -197,13 +197,25 @@ static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
		struct cpuidle_device *dev =
		per_cpu_ptr(pseries_cpuidle_devices, hotcpu);

		switch (action & 0xf) {
		case CPU_ONLINE:
		if (dev && cpuidle_get_driver()) {
		cpuidle_disable_device(dev);
		switch (action) {
		case CPU_ONLINE:
		case CPU_ONLINE_FROZEN:
		cpuidle_pause_and_lock();
		cpuidle_enable_device(dev);
		}
		cpuidle_resume_and_unlock();
		break;

		case CPU_DEAD:
		case CPU_DEAD_FROZEN:
		cpuidle_pause_and_lock();
		cpuidle_disable_device(dev);
		cpuidle_resume_and_unlock();
		break;

		default:
		return NOTIFY_DONE;
		}
		}
		return NOTIFY_OK;
		}
		@@ -345,6 +357,7 @@ static int __init pseries_processor_idle_init(void)
		static void __exit pseries_processor_idle_exit(void)
		{

		unregister_cpu_notifier(&setup_hotplug_notifier);
		pseries_idle_devices_uninit();
		cpuidle_unregister_driver(&pseries_idle_driver);