1 files changed, 11 insertions, 16 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 1911d1729353..246ae147df74 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -78,15 +78,10 @@ static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
 static unsigned int dbs_enable; /* number of CPUs using this policy */
 
 /*
- * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
- * lock and dbs_mutex. cpu_hotplug lock should always be held before
- * dbs_mutex. If any function that can potentially take cpu_hotplug lock
- * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
- * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
- * is recursive for the same process. -Venki
- * DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
- * would deadlock with cancel_delayed_work_sync(), which is needed for proper
- * raceless workqueue teardown.
+ * dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
+ * different CPUs. It protects dbs_enable in governor start/stop. It also
+ * serializes governor limit_change with do_dbs_timer. We do not want
+ * do_dbs_timer to run when user is changing the governor or limits.
  */
 static DEFINE_MUTEX(dbs_mutex);
 
@@ -494,11 +489,10 @@ static void do_dbs_timer(struct work_struct *work)
 
         delay -= jiffies % delay;
 
-        if (lock_policy_rwsem_write(cpu) < 0)
-                return;
+        mutex_lock(&dbs_mutex);
 
         if (!dbs_info->enable) {
-                unlock_policy_rwsem_write(cpu);
+                mutex_unlock(&dbs_mutex);
                 return;
         }
 
@@ -517,7 +511,7 @@ static void do_dbs_timer(struct work_struct *work)
                         dbs_info->freq_lo, CPUFREQ_RELATION_H);
         }
         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
-        unlock_policy_rwsem_write(cpu);
+        mutex_unlock(&dbs_mutex);
 }
 
 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -598,14 +592,15 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                                 max(min_sampling_rate,
                                     latency * LATENCY_MULTIPLIER);
                 }
-                dbs_timer_init(this_dbs_info);
-
                 mutex_unlock(&dbs_mutex);
+
+                dbs_timer_init(this_dbs_info);
                 break;
 
         case CPUFREQ_GOV_STOP:
-                mutex_lock(&dbs_mutex);
                 dbs_timer_exit(this_dbs_info);
+
+                mutex_lock(&dbs_mutex);
                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
                 dbs_enable--;
                 mutex_unlock(&dbs_mutex);