cpufreq: Notify governors when cpus are hot-[un]plugged

Because cpufreq core and governors worry only about the online cpus, if a cpu is
hot [un]plugged, we must notify governors about it, otherwise be ready to expect
something unexpected.

We already have notifiers in the form of CPUFREQ_GOV_START/CPUFREQ_GOV_STOP, we
just need to call them now.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -751,11 +751,16 @@ static int cpufreq_add_dev_policy(unsigned int cpu,
 				return -EBUSY;
 			}
 
+			__cpufreq_governor(managed_policy, CPUFREQ_GOV_STOP);
+
 			spin_lock_irqsave(&cpufreq_driver_lock, flags);
 			cpumask_copy(managed_policy->cpus, policy->cpus);
 			per_cpu(cpufreq_cpu_data, cpu) = managed_policy;
 			spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
+			__cpufreq_governor(managed_policy, CPUFREQ_GOV_START);
+			__cpufreq_governor(managed_policy, CPUFREQ_GOV_LIMITS);
+
 			pr_debug("CPU already managed, adding link\n");
 			ret = sysfs_create_link(&dev->kobj,
 						&managed_policy->kobj,
@@ -1066,8 +1071,13 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
 	 */
 	if (unlikely(cpu != data->cpu)) {
 		pr_debug("removing link\n");
+		__cpufreq_governor(data, CPUFREQ_GOV_STOP);
 		cpumask_clear_cpu(cpu, data->cpus);
 		spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+		__cpufreq_governor(data, CPUFREQ_GOV_START);
+		__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);
+
 		kobj = &dev->kobj;
 		cpufreq_cpu_put(data);
 		unlock_policy_rwsem_write(cpu);