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intel-idle: Fix CPU hotplug callback registration 

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_notifier_register_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_notifier_register_done();

Fix the intel-idle code by using this latter form of callback registration.

Cc: Len Brown <lenb@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srivatsa S. Bhat 2014-03-11 02:10:30 +05:30 committed by Rafael J. Wysocki
parent 8daa127f4e
commit 07494d547e
1 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/idle/intel_idle.c
View File

@ -681,14 +681,19 @@ static int __init intel_idle_init(void)
if (intel_idle_cpuidle_devices == NULL)
return -ENOMEM;
cpu_notifier_register_begin();
for_each_online_cpu(i) {
retval = intel_idle_cpu_init(i);
if (retval) {
cpu_notifier_register_done();
cpuidle_unregister_driver(&intel_idle_driver);
return retval;
}
}
register_cpu_notifier(&cpu_hotplug_notifier);
__register_cpu_notifier(&cpu_hotplug_notifier);
cpu_notifier_register_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_notifier_register_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_notifier_register_done();
return;
}