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hwmon, coretemp: 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 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
View File

@ -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);
}