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

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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>
This commit is contained in:
Silas Boyd-Wickizer 2012-09-23 20:27:32 +02:00 committed by Jean Delvare
parent 1ec3ddfd27
commit 641f145600
1 changed files with 5 additions and 0 deletions
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5
drivers/hwmon/coretemp.c
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@ -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);
}