tree 5feb67adb0a1cda97bd5f09d3ca6d2af20b412aa
parent 180d86463257812dc17e5df912f3bddcc96abb00
author Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> 1394484043 +0530
committer Rafael J. Wysocki <rafael.j.wysocki@intel.com> 1395319426 +0100

octeon, watchdog: 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 watchdog code in octeon by using this latter form of callback
registration.

Cc: Wim Van Sebroeck <wim@iguana.be>
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>