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hwmon, coretemp: 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 hwmon coretemp code by using this latter form of callback
registration.

Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Jean Delvare <jdelvare@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>
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 02:11:11 +05:30 committed by Rafael J. Wysocki
parent cf0485a2ac
commit 3289705fe2
1 changed files with 7 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/hwmon/coretemp.c
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@ -849,20 +849,20 @@ static int __init coretemp_init(void)
if (err)
goto exit;
get_online_cpus();
cpu_notifier_register_begin();
for_each_online_cpu(i)
get_core_online(i);
#ifndef CONFIG_HOTPLUG_CPU
if (list_empty(&pdev_list)) {
put_online_cpus();
cpu_notifier_register_done();
err = -ENODEV;
goto exit_driver_unreg;
}
#endif
register_hotcpu_notifier(&coretemp_cpu_notifier);
put_online_cpus();
__register_hotcpu_notifier(&coretemp_cpu_notifier);
cpu_notifier_register_done();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@ -877,8 +877,8 @@ static void __exit coretemp_exit(void)
{
struct pdev_entry *p, *n;
get_online_cpus();
unregister_hotcpu_notifier(&coretemp_cpu_notifier);
cpu_notifier_register_begin();
__unregister_hotcpu_notifier(&coretemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
platform_device_unregister(p->pdev);
@ -886,7 +886,7 @@ static void __exit coretemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
put_online_cpus();
cpu_notifier_register_done();
platform_driver_unregister(&coretemp_driver);
}