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>
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@ -815,17 +815,20 @@ static int __init coretemp_init(void)
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if (err)
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goto exit;
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get_online_cpus();
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for_each_online_cpu(i)
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get_core_online(i);
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#ifndef CONFIG_HOTPLUG_CPU
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if (list_empty(&pdev_list)) {
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put_online_cpus();
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err = -ENODEV;
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goto exit_driver_unreg;
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}
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#endif
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register_hotcpu_notifier(&coretemp_cpu_notifier);
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put_online_cpus();
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return 0;
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#ifndef CONFIG_HOTPLUG_CPU
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@ -840,6 +843,7 @@ static void __exit coretemp_exit(void)
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{
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struct pdev_entry *p, *n;
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get_online_cpus();
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unregister_hotcpu_notifier(&coretemp_cpu_notifier);
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mutex_lock(&pdev_list_mutex);
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list_for_each_entry_safe(p, n, &pdev_list, list) {
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@ -848,6 +852,7 @@ static void __exit coretemp_exit(void)
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kfree(p);
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}
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mutex_unlock(&pdev_list_mutex);
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put_online_cpus();
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platform_driver_unregister(&coretemp_driver);
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}
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