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Code Issues Releases Wiki Activity

powerpc, sysfs: 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 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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/powerpc/kernel/sysfs.c
View File

@ -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 */