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hwmon, via-cputemp: 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 via-cputemp code by using this latter form of callback
registration.

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>
wifi-calibration
Srivatsa S. Bhat 2014-03-11 02:11:33 +05:30 committed by Rafael J. Wysocki
parent 3289705fe2
commit 2480b6a3e5
1 changed files with 7 additions and 7 deletions
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14
drivers/hwmon/via-cputemp.c
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@ -319,7 +319,7 @@ static int __init via_cputemp_init(void)
if (err)
goto exit;
get_online_cpus();
cpu_notifier_register_begin();
for_each_online_cpu(i) {
struct cpuinfo_x86 *c = &cpu_data(i);
@ -339,14 +339,14 @@ static int __init via_cputemp_init(void)
#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(&via_cputemp_cpu_notifier);
put_online_cpus();
__register_hotcpu_notifier(&via_cputemp_cpu_notifier);
cpu_notifier_register_done();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@ -361,8 +361,8 @@ static void __exit via_cputemp_exit(void)
{
struct pdev_entry *p, *n;
get_online_cpus();
unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
cpu_notifier_register_begin();
__unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
platform_device_unregister(p->pdev);
@ -370,7 +370,7 @@ static void __exit via_cputemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
put_online_cpus();
cpu_notifier_register_done();
platform_driver_unregister(&via_cputemp_driver);
}