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sparc, sysfs: 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 sysfs code in sparc by using this latter form of callback
registration.

Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
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 02:06:09 +05:30 committed by Rafael J. Wysocki
parent f4edbcd5d1
commit 1e0b0c4c6b
1 changed files with 5 additions and 1 deletions
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6
arch/sparc/kernel/sysfs.c
View File

@ -300,7 +300,7 @@ static int __init topology_init(void)
check_mmu_stats();
register_cpu_notifier(&sysfs_cpu_nb);
cpu_notifier_register_begin();
for_each_possible_cpu(cpu) {
struct cpu *c = &per_cpu(cpu_devices, cpu);
@ -310,6 +310,10 @@ static int __init topology_init(void)
register_cpu_online(cpu);
}
__register_cpu_notifier(&sysfs_cpu_nb);
cpu_notifier_register_done();
return 0;
}