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x86, cpuid: 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 cpuid code in x86 by using this latter form of callback registration.

Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 02:06:44 +05:30 committed by Rafael J. Wysocki
parent de82a01bef
commit 4b660b384d
1 changed files with 8 additions and 7 deletions
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15
arch/x86/kernel/cpuid.c
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@ -198,14 +198,15 @@ static int __init cpuid_init(void)
goto out_chrdev;
}
cpuid_class->devnode = cpuid_devnode;
get_online_cpus();
cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = cpuid_device_create(i);
if (err != 0)
goto out_class;
}
register_hotcpu_notifier(&cpuid_class_cpu_notifier);
put_online_cpus();
__register_hotcpu_notifier(&cpuid_class_cpu_notifier);
cpu_notifier_register_done();
err = 0;
goto out;
@ -215,7 +216,7 @@ static int __init cpuid_init(void)
for_each_online_cpu(i) {
cpuid_device_destroy(i);
}
put_online_cpus();
cpu_notifier_register_done();
class_destroy(cpuid_class);
out_chrdev:
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
@ -227,13 +228,13 @@ static void __exit cpuid_exit(void)
{
int cpu = 0;
get_online_cpus();
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
cpuid_device_destroy(cpu);
class_destroy(cpuid_class);
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
put_online_cpus();
__unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
cpu_notifier_register_done();
}
module_init(cpuid_init);