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Commit 641f1456 authored by Silas Boyd-Wickizer's avatar Silas Boyd-Wickizer Committed by Jean Delvare
Browse files

hwmon: (coretemp) Use get_online_cpus to avoid races involving CPU hotplug 



coretemp_init loops with for_each_online_cpu, adding platform_devices
and sysfs interfaces, then calls register_hotcpu_notifier.  There is a
race if a CPU is offlined or onlined after the loop, but before
register_hotcpu_notifier.  The race might result in the absence of a
platform_device+sysfs interface for an online CPU, or the presence of
a platform_device+sysfs interface for an offline CPU.  A similar race
occurs during coretemp_exit, after the module calls
unregister_hotcpu_notifier, but before it unregisters all devices, a
CPU might offline and a device for an offline CPU will exist for a
short while.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier
with get_online_cpus+put_online_cpus; and surrounds
unregister_hotcpu_notifier and device unregistering with
get_online_cpus+put_online_cpus.

Build tested.

Signed-off-by: default avatarSilas Boyd-Wickizer <sbw@mit.edu>
Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent 1ec3ddfd

drivers/hwmon/coretemp.c

+5 −0
Original line number Diff line number Diff line
@@ -815,17 +815,20 @@ static int __init coretemp_init(void) 
	if (err)

		goto exit;



	get_online_cpus();

	for_each_online_cpu(i)

		get_core_online(i);



#ifndef CONFIG_HOTPLUG_CPU

	if (list_empty(&pdev_list)) {

		put_online_cpus();

		err = -ENODEV;

		goto exit_driver_unreg;

	}

#endif



	register_hotcpu_notifier(&coretemp_cpu_notifier);

	put_online_cpus();

	return 0;



#ifndef CONFIG_HOTPLUG_CPU
@@ -840,6 +843,7 @@ static void __exit coretemp_exit(void) 
{

	struct pdev_entry *p, *n;



	get_online_cpus();

	unregister_hotcpu_notifier(&coretemp_cpu_notifier);

	mutex_lock(&pdev_list_mutex);

	list_for_each_entry_safe(p, n, &pdev_list, list) {
@@ -848,6 +852,7 @@ static void __exit coretemp_exit(void) 
		kfree(p);

	}

	mutex_unlock(&pdev_list_mutex);

	put_online_cpus();

	platform_driver_unregister(&coretemp_driver);

}