Commit 641f1456 authored Sep 23, 2012 by Silas Boyd-Wickizer Committed by Jean Delvare Sep 23, 2012

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: Silas Boyd-Wickizer <sbw@mit.edu>
Signed-off-by: Jean 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);
		}

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