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>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 24e4ba568e77..0f4e96ff99e8 100644
--- 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);