cpufreq / stats: fix race between stats allocation and first usage

This patch forces complete struct cpufreq_stats allocation for all cpus before
registering CPUFREQ_TRANSITION_NOTIFIER notifier, otherwise in some conditions
cpufreq_stat_notifier_trans() can be called in the middle of stats allocation,
in this case cpufreq_stats_table already exists, but stat->freq_table is NULL.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index e40e50809644..9d7732b81044 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -364,18 +364,21 @@ static int __init cpufreq_stats_init(void)
         if (ret)
                 return ret;
 
+        register_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
+        for_each_online_cpu(cpu)
+                cpufreq_update_policy(cpu);
+
         ret = cpufreq_register_notifier(&notifier_trans_block,
                                 CPUFREQ_TRANSITION_NOTIFIER);
         if (ret) {
                 cpufreq_unregister_notifier(&notifier_policy_block,
                                 CPUFREQ_POLICY_NOTIFIER);
+                unregister_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
+                for_each_online_cpu(cpu)
+                        cpufreq_stats_free_table(cpu);
                 return ret;
         }
 
-        register_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
-        for_each_online_cpu(cpu) {
-                cpufreq_update_policy(cpu);
-        }
         return 0;
 }
 static void __exit cpufreq_stats_exit(void)