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s390, cacheinfo: 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 cacheinfo code in s390 by using this latter form of callback
registration.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
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 02:05:46 +05:30 committed by Rafael J. Wysocki
parent 8146875de7
commit 6575080e67
1 changed files with 4 additions and 1 deletions
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5
arch/s390/kernel/cache.c
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@ -378,9 +378,12 @@ static int __init cache_init(void)
if (!test_facility(34))
return 0;
cache_build_info();
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
cache_add_cpu(cpu);
hotcpu_notifier(cache_hotplug, 0);
__hotcpu_notifier(cache_hotplug, 0);
cpu_notifier_register_done();
return 0;
}
device_initcall(cache_init);