cpufreq: Restart governor as soon as possible

__cpufreq_remove_dev_finish() is doing two things today:
- Restarts the governor if some CPUs from concerned policy are still
  online.
- Frees the policy if all CPUs are offline.

The first task of restarting the governor can be moved to
__cpufreq_remove_dev_prepare() to restart the governor early. There is
no race between _prepare() and _finish() as they would be handling
completely different cases. _finish() will only be required if we are
going to free the policy and that has nothing to do with restarting the
governor.

Original-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 8b81007..c355ab6 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1428,8 +1428,8 @@ nomem_out:
 static int __cpufreq_remove_dev_prepare(struct device *dev,
                                        struct subsys_interface *sif)
 {
-       unsigned int cpu = dev->id, cpus;
-       int ret;
+       unsigned int cpu = dev->id;
+       int ret = 0;
        struct cpufreq_policy *policy;
 
        pr_debug("%s: unregistering CPU %u\n", __func__, cpu);
@@ -1449,23 +1449,33 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
        }
 
        down_write(&policy->rwsem);
-       cpus = cpumask_weight(policy->cpus);
+       cpumask_clear_cpu(cpu, policy->cpus);
 
-       if (has_target() && cpus == 1)
-               strncpy(policy->last_governor, policy->governor->name,
-                       CPUFREQ_NAME_LEN);
+       if (policy_is_inactive(policy)) {
+               if (has_target())
+                       strncpy(policy->last_governor, policy->governor->name,
+                               CPUFREQ_NAME_LEN);
+       } else if (cpu == policy->cpu) {
+               /* Nominate new CPU */
+               policy->cpu = cpumask_any(policy->cpus);
+       }
        up_write(&policy->rwsem);
 
-       if (cpu != policy->cpu)
-               return 0;
+       /* Start governor again for active policy */
+       if (!policy_is_inactive(policy)) {
+               if (has_target()) {
+                       ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
+                       if (!ret)
+                               ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
 
-       if (cpus > 1)
-               /* Nominate new CPU */
-               update_policy_cpu(policy, cpumask_any_but(policy->cpus, cpu));
-       else if (cpufreq_driver->stop_cpu)
+                       if (ret)
+                               pr_err("%s: Failed to start governor\n", __func__);
+               }
+       } else if (cpufreq_driver->stop_cpu) {
                cpufreq_driver->stop_cpu(policy);
+       }
 
-       return 0;
+       return ret;
 }
 
 static int __cpufreq_remove_dev_finish(struct device *dev,
@@ -1473,33 +1483,16 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
 {
        unsigned int cpu = dev->id;
        int ret;
-       struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
+       struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);
 
        if (!policy) {
                pr_debug("%s: No cpu_data found\n", __func__);
                return -EINVAL;
        }
 
-       down_write(&policy->rwsem);
-       cpumask_clear_cpu(cpu, policy->cpus);
-       up_write(&policy->rwsem);
-
-       /* Not the last cpu of policy, start governor again ? */
-       if (!policy_is_inactive(policy)) {
-               if (!has_target())
-                       return 0;
-
-               ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
-               if (!ret)
-                       ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
-
-               if (ret) {
-                       pr_err("%s: Failed to start governor\n", __func__);
-                       return ret;
-               }
-
+       /* Only proceed for inactive policies */
+       if (!policy_is_inactive(policy))
                return 0;
-       }
 
        /* If cpu is last user of policy, free policy */
        if (has_target()) {