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

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
......@@ -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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