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hwmon: (via-cputemp) Use get_online_cpus to avoid races involving CPU hotplug

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via_cputemp_init loops with for_each_online_cpu, adding
platform_devices, then calls register_hotcpu_notifier.  If a CPU is
offlined between the loop and register_hotcpu_notifier, then later
onlined, via_cputemp_device_add will attempt to add platform devices
with the same ID.  A similar race occurs during via_cputemp_exit,
after the module calls unregister_hotcpu_notifier, a CPU might offline
and a device will exist for a CPU that is offline.

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>
Acked-by: Harald Welte <laforge@gnumonks.org>
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 e5e77cf9f9
commit 1ec3ddfd27
1 changed files with 5 additions and 0 deletions
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5
drivers/hwmon/via-cputemp.c
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@ -328,6 +328,7 @@ static int __init via_cputemp_init(void)
if (err)
goto exit;
get_online_cpus();
for_each_online_cpu(i) {
struct cpuinfo_x86 *c = &cpu_data(i);
@ -347,12 +348,14 @@ static int __init via_cputemp_init(void)
#ifndef CONFIG_HOTPLUG_CPU
if (list_empty(&pdev_list)) {
put_online_cpus();
err = -ENODEV;
goto exit_driver_unreg;
}
#endif
register_hotcpu_notifier(&via_cputemp_cpu_notifier);
put_online_cpus();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@ -367,6 +370,7 @@ static void __exit via_cputemp_exit(void)
{
struct pdev_entry *p, *n;
get_online_cpus();
unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
@ -375,6 +379,7 @@ static void __exit via_cputemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
put_online_cpus();
platform_driver_unregister(&via_cputemp_driver);
}