1 files changed, 23 insertions, 20 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 929e193..da7f351 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -189,7 +189,7 @@ static void od_check_cpu(int cpu, unsigned int load)
 	}
 }
 
-static unsigned int od_dbs_timer(struct cpufreq_policy *policy, bool modify_all)
+static unsigned int od_dbs_timer(struct cpufreq_policy *policy)
 {
 	struct dbs_data *dbs_data = policy->governor_data;
 	unsigned int cpu = policy->cpu;
@@ -198,9 +198,6 @@ static unsigned int od_dbs_timer(struct cpufreq_policy *policy, bool modify_all)
 	struct od_dbs_tuners *od_tuners = dbs_data->tuners;
 	int delay = 0, sample_type = dbs_info->sample_type;
 
-	if (!modify_all)
-		goto max_delay;
-
 	/* Common NORMAL_SAMPLE setup */
 	dbs_info->sample_type = OD_NORMAL_SAMPLE;
 	if (sample_type == OD_SUB_SAMPLE) {
@@ -216,7 +213,6 @@ static unsigned int od_dbs_timer(struct cpufreq_policy *policy, bool modify_all)
 		}
 	}
 
-max_delay:
 	if (!delay)
 		delay = delay_for_sampling_rate(od_tuners->sampling_rate
 				* dbs_info->rate_mult);
@@ -262,7 +258,6 @@ static void update_sampling_rate(struct dbs_data *dbs_data,
 		struct od_cpu_dbs_info_s *dbs_info;
 		struct cpu_dbs_info *cdbs;
 		struct cpu_common_dbs_info *shared;
-		unsigned long next_sampling, appointed_at;
 
 		dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
 		cdbs = &dbs_info->cdbs;
@@ -286,20 +281,28 @@ static void update_sampling_rate(struct dbs_data *dbs_data,
 		 * policy will be governed by dbs_data, otherwise there can be
 		 * multiple policies that are governed by the same dbs_data.
 		 */
-		if (dbs_data != policy->governor_data)
-			continue;
-
-		/*
-		 * Checking this for any CPU should be fine, timers for all of
-		 * them are scheduled together.
-		 */
-		next_sampling = jiffies + usecs_to_jiffies(new_rate);
-		appointed_at = dbs_info->cdbs.timer.expires;
-
-		if (time_before(next_sampling, appointed_at)) {
-			gov_cancel_work(shared);
-			gov_add_timers(policy, usecs_to_jiffies(new_rate));
-
+		if (dbs_data == policy->governor_data) {
+			mutex_lock(&shared->timer_mutex);
+			/*
+			 * On 32-bit architectures this may race with the
+			 * sample_delay_ns read in dbs_update_util_handler(),
+			 * but that really doesn't matter.  If the read returns
+			 * a value that's too big, the sample will be skipped,
+			 * but the next invocation of dbs_update_util_handler()
+			 * (when the update has been completed) will take a
+			 * sample.  If the returned value is too small, the
+			 * sample will be taken immediately, but that isn't a
+			 * problem, as we want the new rate to take effect
+			 * immediately anyway.
+			 *
+			 * If this runs in parallel with dbs_work_handler(), we
+			 * may end up overwriting the sample_delay_ns value that
+			 * it has just written, but the difference should not be
+			 * too big and it will be corrected next time a sample
+			 * is taken, so it shouldn't be significant.
+			 */
+			gov_update_sample_delay(shared, new_rate);
+			mutex_unlock(&shared->timer_mutex);
 		}
 	}