[CPUFREQ] Cleanup locking in ondemand governor

Redesign the locking inside ondemand driver. Make dbs_mutex handle all the
global state changes inside the driver and invent a new percpu mutex
to serialize percpu timer and frequency limit change.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 27 insertions, 35 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 246ae147df74..d6ba14276bb1 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -70,8 +70,13 @@ struct cpu_dbs_info_s {
         unsigned int freq_lo_jiffies;
         unsigned int freq_hi_jiffies;
         int cpu;
-        unsigned int enable:1,
-                sample_type:1;
+        unsigned int sample_type:1;
+        /*
+         * percpu mutex that serializes governor limit change with
+         * do_dbs_timer invocation. We do not want do_dbs_timer to run
+         * when user is changing the governor or limits.
+         */
+        struct mutex timer_mutex;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
 
@@ -79,9 +84,7 @@ static unsigned int dbs_enable;	/* number of CPUs using this policy */
 
 /*
  * 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.
+ * different CPUs. It protects dbs_enable in governor start/stop.
  */
 static DEFINE_MUTEX(dbs_mutex);
 
@@ -187,13 +190,18 @@ static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
         return freq_hi;
 }
 
+static void ondemand_powersave_bias_init_cpu(int cpu)
+{
+        struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+        dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
+        dbs_info->freq_lo = 0;
+}
+
 static void ondemand_powersave_bias_init(void)
 {
         int i;
         for_each_online_cpu(i) {
-                struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
-                dbs_info->freq_table = cpufreq_frequency_get_table(i);
-                dbs_info->freq_lo = 0;
+                ondemand_powersave_bias_init_cpu(i);
         }
 }
 
@@ -235,12 +243,10 @@ static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
         unsigned int input;
         int ret;
         ret = sscanf(buf, "%u", &input);
+        if (ret != 1)
+                return -EINVAL;
 
         mutex_lock(&dbs_mutex);
-        if (ret != 1) {
-                mutex_unlock(&dbs_mutex);
-                return -EINVAL;
-        }
         dbs_tuners_ins.sampling_rate = max(input, min_sampling_rate);
         mutex_unlock(&dbs_mutex);
 
@@ -254,13 +260,12 @@ static ssize_t store_up_threshold(struct cpufreq_policy *unused,
         int ret;
         ret = sscanf(buf, "%u", &input);
 
-        mutex_lock(&dbs_mutex);
         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
                         input < MIN_FREQUENCY_UP_THRESHOLD) {
-                mutex_unlock(&dbs_mutex);
                 return -EINVAL;
         }
 
+        mutex_lock(&dbs_mutex);
         dbs_tuners_ins.up_threshold = input;
         mutex_unlock(&dbs_mutex);
 
@@ -358,9 +363,6 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
         struct cpufreq_policy *policy;
         unsigned int j;
 
-        if (!this_dbs_info->enable)
-                return;
-
         this_dbs_info->freq_lo = 0;
         policy = this_dbs_info->cur_policy;
 
@@ -488,13 +490,7 @@ static void do_dbs_timer(struct work_struct *work)
         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 
         delay -= jiffies % delay;
-
-        mutex_lock(&dbs_mutex);
-
-        if (!dbs_info->enable) {
-                mutex_unlock(&dbs_mutex);
-                return;
-        }
+        mutex_lock(&dbs_info->timer_mutex);
 
         /* Common NORMAL_SAMPLE setup */
         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
@@ -511,7 +507,7 @@ 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);
-        mutex_unlock(&dbs_mutex);
+        mutex_unlock(&dbs_info->timer_mutex);
 }
 
 static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -520,8 +516,6 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
         int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
         delay -= jiffies % delay;
 
-        dbs_info->enable = 1;
-        ondemand_powersave_bias_init();
         dbs_info->sample_type = DBS_NORMAL_SAMPLE;
         INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
         queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
@@ -530,7 +524,6 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 
 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 {
-        dbs_info->enable = 0;
         cancel_delayed_work_sync(&dbs_info->work);
 }
 
@@ -549,19 +542,15 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                 if ((!cpu_online(cpu)) || (!policy->cur))
                         return -EINVAL;
 
-                if (this_dbs_info->enable) /* Already enabled */
-                        break;
-
                 mutex_lock(&dbs_mutex);
-                dbs_enable++;
 
                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
                 if (rc) {
-                        dbs_enable--;
                         mutex_unlock(&dbs_mutex);
                         return rc;
                 }
 
+                dbs_enable++;
                 for_each_cpu(j, policy->cpus) {
                         struct cpu_dbs_info_s *j_dbs_info;
                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
@@ -575,6 +564,8 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                         }
                 }
                 this_dbs_info->cpu = cpu;
+                ondemand_powersave_bias_init_cpu(cpu);
+                mutex_init(&this_dbs_info->timer_mutex);
                 /*
                  * Start the timerschedule work, when this governor
                  * is used for first time
@@ -602,20 +593,21 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 
                 mutex_lock(&dbs_mutex);
                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
+                mutex_destroy(&this_dbs_info->timer_mutex);
                 dbs_enable--;
                 mutex_unlock(&dbs_mutex);
 
                 break;
 
         case CPUFREQ_GOV_LIMITS:
-                mutex_lock(&dbs_mutex);
+                mutex_lock(&this_dbs_info->timer_mutex);
                 if (policy->max < this_dbs_info->cur_policy->cur)
                         __cpufreq_driver_target(this_dbs_info->cur_policy,
                                 policy->max, CPUFREQ_RELATION_H);
                 else if (policy->min > this_dbs_info->cur_policy->cur)
                         __cpufreq_driver_target(this_dbs_info->cur_policy,
                                 policy->min, CPUFREQ_RELATION_L);
-                mutex_unlock(&dbs_mutex);
+                mutex_unlock(&this_dbs_info->timer_mutex);
                 break;
         }
         return 0;