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x86, therm_throt.c: Fix CPU hotplug callback registration

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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 thermal throttle code in x86 by using this latter form of callback
registration.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
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 02:07:21 +05:30 committed by Rafael J. Wysocki
parent 82a8f131aa
commit 4e6192bbec
1 changed files with 4 additions and 1 deletions
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5
arch/x86/kernel/cpu/mcheck/therm_throt.c
View file

@ -319,7 +319,7 @@ static __init int thermal_throttle_init_device(void)
if (!atomic_read(&therm_throt_en))
return 0;
register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
cpu_notifier_register_begin();
#ifdef CONFIG_HOTPLUG_CPU
mutex_lock(&therm_cpu_lock);
@ -333,6 +333,9 @@ static __init int thermal_throttle_init_device(void)
mutex_unlock(&therm_cpu_lock);
#endif
__register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
cpu_notifier_register_done();
return 0;
}
device_initcall(thermal_throttle_init_device);