cpufreq: Lock CPU online/offline in cpufreq_register_driver()

To protect against races with concurrent CPU online/offline, call
get_online_cpus() before registering a cpufreq driver.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 24e4ba568e7725cd04d68cca0e2073308efd0bbf..0f4e96ff99e8735eab3b39e66669dd09d99b874d 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2471,10 +2471,14 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 
        pr_debug("trying to register driver %s\n", driver_data->name);
 
+       /* Protect against concurrent CPU online/offline. */
+       get_online_cpus();
+
        write_lock_irqsave(&cpufreq_driver_lock, flags);
        if (cpufreq_driver) {
                write_unlock_irqrestore(&cpufreq_driver_lock, flags);
-               return -EEXIST;
+               ret = -EEXIST;
+               goto out;
        }
        cpufreq_driver = driver_data;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
@@ -2513,7 +2517,10 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
        register_hotcpu_notifier(&cpufreq_cpu_notifier);
        pr_debug("driver %s up and running\n", driver_data->name);
 
-       return 0;
+out:
+       put_online_cpus();
+       return ret;
+
 err_if_unreg:
        subsys_interface_unregister(&cpufreq_interface);
 err_boost_unreg:
@@ -2523,7 +2530,7 @@ err_null_driver:
        write_lock_irqsave(&cpufreq_driver_lock, flags);
        cpufreq_driver = NULL;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
-       return ret;
+       goto out;
 }
 EXPORT_SYMBOL_GPL(cpufreq_register_driver);