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x86, intel, uncore: 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 uncore code in intel-x86 by using this latter form of callback
registration.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
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 02:06:57 +05:30 committed by Rafael J. Wysocki
parent 42112a0f5d
commit 2c666adacc
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kernel/cpu/perf_event_intel_uncore.c
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@ -3817,7 +3817,7 @@ static int __init uncore_cpu_init(void)
if (ret)
return ret;
get_online_cpus();
cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
int i, phys_id = topology_physical_package_id(cpu);
@ -3836,9 +3836,9 @@ static int __init uncore_cpu_init(void)
}
on_each_cpu(uncore_cpu_setup, NULL, 1);
register_cpu_notifier(&uncore_cpu_nb);
__register_cpu_notifier(&uncore_cpu_nb);
put_online_cpus();
cpu_notifier_register_done();
return 0;
}