hwmon, via-cputemp: Fix CPU hotplug callback registration
Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the hwmon via-cputemp code by using this latter form of callback registration. Cc: Jean Delvare <jdelvare@suse.de> Cc: Ingo Molnar <mingo@kernel.org> Acked-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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3289705fe2
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2480b6a3e5
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@ -319,7 +319,7 @@ static int __init via_cputemp_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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cpu_notifier_register_begin();
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for_each_online_cpu(i) {
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struct cpuinfo_x86 *c = &cpu_data(i);
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@ -339,14 +339,14 @@ static int __init via_cputemp_init(void)
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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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cpu_notifier_register_done();
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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(&via_cputemp_cpu_notifier);
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put_online_cpus();
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__register_hotcpu_notifier(&via_cputemp_cpu_notifier);
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cpu_notifier_register_done();
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return 0;
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#ifndef CONFIG_HOTPLUG_CPU
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@ -361,8 +361,8 @@ static void __exit via_cputemp_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(&via_cputemp_cpu_notifier);
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cpu_notifier_register_begin();
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__unregister_hotcpu_notifier(&via_cputemp_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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platform_device_unregister(p->pdev);
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@ -370,7 +370,7 @@ static void __exit via_cputemp_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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cpu_notifier_register_done();
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platform_driver_unregister(&via_cputemp_driver);
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}
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