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powerpc, sysfs: 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 sysfs code in powerpc by using this latter form of callback
registration.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Wang Dongsheng <dongsheng.wang@freescale.com>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.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 02:06:31 +05:30 committed by Rafael J. Wysocki
parent 1e0b0c4c6b
commit d1a5511390
1 changed files with 7 additions and 1 deletions
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8
arch/powerpc/kernel/sysfs.c
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@ -975,7 +975,8 @@ static int __init topology_init(void)
int cpu;
register_nodes();
register_cpu_notifier(&sysfs_cpu_nb);
cpu_notifier_register_begin();
for_each_possible_cpu(cpu) {
struct cpu *c = &per_cpu(cpu_devices, cpu);
@ -999,6 +1000,11 @@ static int __init topology_init(void)
if (cpu_online(cpu))
register_cpu_online(cpu);
}
__register_cpu_notifier(&sysfs_cpu_nb);
cpu_notifier_register_done();
#ifdef CONFIG_PPC64
sysfs_create_dscr_default();
#endif /* CONFIG_PPC64 */