From 3289705fe2b429569f37730ecf660719b8924420 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:11:11 +0530 Subject: [PATCH] hwmon, coretemp: 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 coretemp code by using this latter form of callback registration. Cc: Fenghua Yu Cc: Jean Delvare Cc: Ingo Molnar Acked-by: Guenter Roeck Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- drivers/hwmon/coretemp.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c index bbb0b0d463f7..746a6ad8525f 100644 --- a/drivers/hwmon/coretemp.c +++ b/drivers/hwmon/coretemp.c @@ -849,20 +849,20 @@ static int __init coretemp_init(void) if (err) goto exit; - get_online_cpus(); + cpu_notifier_register_begin(); for_each_online_cpu(i) get_core_online(i); #ifndef CONFIG_HOTPLUG_CPU if (list_empty(&pdev_list)) { - put_online_cpus(); + cpu_notifier_register_done(); err = -ENODEV; goto exit_driver_unreg; } #endif - register_hotcpu_notifier(&coretemp_cpu_notifier); - put_online_cpus(); + __register_hotcpu_notifier(&coretemp_cpu_notifier); + cpu_notifier_register_done(); return 0; #ifndef CONFIG_HOTPLUG_CPU @@ -877,8 +877,8 @@ static void __exit coretemp_exit(void) { struct pdev_entry *p, *n; - get_online_cpus(); - unregister_hotcpu_notifier(&coretemp_cpu_notifier); + cpu_notifier_register_begin(); + __unregister_hotcpu_notifier(&coretemp_cpu_notifier); mutex_lock(&pdev_list_mutex); list_for_each_entry_safe(p, n, &pdev_list, list) { platform_device_unregister(p->pdev); @@ -886,7 +886,7 @@ static void __exit coretemp_exit(void) kfree(p); } mutex_unlock(&pdev_list_mutex); - put_online_cpus(); + cpu_notifier_register_done(); platform_driver_unregister(&coretemp_driver); } -- 2.39.2