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x86, amd, ibs: 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 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
View File

@ -926,13 +926,13 @@ static __init int amd_ibs_init(void)
goto out;
perf_ibs_pm_init();
get_online_cpus();
cpu_notifier_register_begin();
ibs_caps = caps;
/* make ibs_caps visible to other cpus: */
smp_mb();
perf_cpu_notifier(perf_ibs_cpu_notifier);
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();
out: