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x86, amd, ibs: 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 amd-ibs code in 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 02:07:45 +05:30 committed by Rafael J. Wysocki
parent 7b7139d4ab
commit 047868ce29
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kernel/cpu/perf_event_amd_ibs.c
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@ -926,13 +926,13 @@ static __init int amd_ibs_init(void)
goto out; goto out;
perf_ibs_pm_init(); perf_ibs_pm_init();
get_online_cpus(); cpu_notifier_register_begin();
ibs_caps = caps; ibs_caps = caps;
/* make ibs_caps visible to other cpus: */ /* make ibs_caps visible to other cpus: */
smp_mb(); smp_mb();
perf_cpu_notifier(perf_ibs_cpu_notifier);
smp_call_function(setup_APIC_ibs, NULL, 1); smp_call_function(setup_APIC_ibs, NULL, 1);
put_online_cpus(); __perf_cpu_notifier(perf_ibs_cpu_notifier);
cpu_notifier_register_done();
ret = perf_event_ibs_init(); ret = perf_event_ibs_init();
out: out: