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Code Issues Releases Wiki Activity

s390, cacheinfo: 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 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
View File

@ -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);