[PATCH v2] cpufreq: stats: Walk online CPUs with CPU offline/online locked

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>

Loops over online CPUs in cpufreq_stats_init() and cpufreq_stats_exit()
should be carried out with CPU offline/online locked or races are
possible otherwise, so make that happen.

Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
---

v1 -> v2: On a second thought, add the policy notifier in cpufreq_stats_init()
  with CPU offline/online locked too.

---
 drivers/cpufreq/cpufreq_stats.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq_stats.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_stats.c
+++ linux-pm/drivers/cpufreq/cpufreq_stats.c
@@ -317,10 +317,13 @@ static int __init cpufreq_stats_init(voi
        unsigned int cpu;
 
        spin_lock_init(&cpufreq_stats_lock);
+
+       get_online_cpus();
+
        ret = cpufreq_register_notifier(&notifier_policy_block,
                                CPUFREQ_POLICY_NOTIFIER);
        if (ret)
-               return ret;
+               goto out;
 
        for_each_online_cpu(cpu)
                cpufreq_stats_create_table(cpu);
@@ -332,21 +335,28 @@ static int __init cpufreq_stats_init(voi
                                CPUFREQ_POLICY_NOTIFIER);
                for_each_online_cpu(cpu)
                        cpufreq_stats_free_table(cpu);
-               return ret;
        }
 
-       return 0;
+ out:
+       put_online_cpus();
+
+       return ret;
 }
 static void __exit cpufreq_stats_exit(void)
 {
        unsigned int cpu;
 
+       get_online_cpus();
+
        cpufreq_unregister_notifier(&notifier_policy_block,
                        CPUFREQ_POLICY_NOTIFIER);
        cpufreq_unregister_notifier(&notifier_trans_block,
                        CPUFREQ_TRANSITION_NOTIFIER);
+
        for_each_online_cpu(cpu)
                cpufreq_stats_free_table(cpu);
+
+       put_online_cpus();
 }
 
 MODULE_AUTHOR("Zou Nan hai <nanhai....@intel.com>");