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ia64, salinfo: Fix 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 salinfo code in ia64 by using this latter form of callback
registration.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.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 02:04:45 +05:30 committed by Rafael J. Wysocki
parent f0bdb5e0c7
commit eff722b06b
1 changed files with 5 additions and 1 deletions
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6
arch/ia64/kernel/salinfo.c
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@ -635,6 +635,8 @@ salinfo_init(void)
(void *)salinfo_entries[i].feature);
}
cpu_notifier_register_begin();
for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) {
data = salinfo_data + i;
data->type = i;
@ -669,7 +671,9 @@ salinfo_init(void)
salinfo_timer.function = &salinfo_timeout;
add_timer(&salinfo_timer);
register_hotcpu_notifier(&salinfo_cpu_notifier);
__register_hotcpu_notifier(&salinfo_cpu_notifier);
cpu_notifier_register_done();
return 0;
}