Messages in this thread Patch in this message |  | | From | "Srivatsa S. Bhat" <> | Subject | [PATCH v2 44/52] hwmon, coretemp: Fix CPU hotplug callback registration | Date | Fri, 14 Feb 2014 13:29:09 +0530 |
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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 <fenghua.yu@intel.com> Cc: Jean Delvare <jdelvare@suse.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: lm-sensors@lm-sensors.org Acked-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> ---
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 bbb0b0d..746a6ad 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); }
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