[CPUFREQ] Restore previously used governor on a hot-replugged CPU

Negative side effect: needs NR_CPUs pointer array of memory in
CONFIG_HOTPLUG_CPU case.

Still needs userspace track keeping and rewriting of governors if governors
change while a CPU is not active (always the governor at CPU remove time is
restored).

Move of policy->user_policy.governor assignment is just a minor cleanup.
http://bugzilla.kernel.org/show_bug.cgi?id=8671Signed-off-by: NThomas Renninger <trenn@suse.de>
Signed-off-by: NMattia Dongili <malattia@linux.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NDave Jones <davej@redhat.com>

drivers/cpufreq/cpufreq.c

@@ -39,6 +39,10 @@
  */
 static struct cpufreq_driver *cpufreq_driver;
 static struct cpufreq_policy *cpufreq_cpu_data[NR_CPUS];
+#ifdef CONFIG_HOTPLUG_CPU
+/* This one keeps track of the previously set governor of a removed CPU */
+static struct cpufreq_governor *cpufreq_cpu_governor[NR_CPUS];
+#endif
 static DEFINE_SPINLOCK(cpufreq_driver_lock);
 
 /*
@@ -770,9 +774,17 @@ static int cpufreq_add_dev (struct sys_device * sys_dev)
 	}
 	policy->user_policy.min = policy->cpuinfo.min_freq;
 	policy->user_policy.max = policy->cpuinfo.max_freq;
-	policy->user_policy.governor = policy->governor;
 
 #ifdef CONFIG_SMP
+
+#ifdef CONFIG_HOTPLUG_CPU
+	if (cpufreq_cpu_governor[cpu]){
+		policy->governor = cpufreq_cpu_governor[cpu];
+		dprintk("Restoring governor %s for cpu %d\n",
+		       policy->governor->name, cpu);
+	}
+#endif
+
 	for_each_cpu_mask(j, policy->cpus) {
 		if (cpu == j)
 			continue;
@@ -873,6 +885,7 @@ static int cpufreq_add_dev (struct sys_device * sys_dev)
 	/* set default policy */
 	ret = __cpufreq_set_policy(policy, &new_policy);
 	policy->user_policy.policy = policy->policy;
+	policy->user_policy.governor = policy->governor;
 
 	unlock_policy_rwsem_write(cpu);
 
@@ -969,6 +982,11 @@ static int __cpufreq_remove_dev (struct sys_device * sys_dev)
 	}
 
 #ifdef CONFIG_SMP
+
+#ifdef CONFIG_HOTPLUG_CPU
+	cpufreq_cpu_governor[cpu] = data->governor;
+#endif
+
 	/* if we have other CPUs still registered, we need to unlink them,
 	 * or else wait_for_completion below will lock up. Clean the
 	 * cpufreq_cpu_data[] while holding the lock, and remove the sysfs
@@ -989,6 +1007,9 @@ static int __cpufreq_remove_dev (struct sys_device * sys_dev)
 			if (j == cpu)
 				continue;
 			dprintk("removing link for cpu %u\n", j);
+#ifdef CONFIG_HOTPLUG_CPU
+			cpufreq_cpu_governor[j] = data->governor;
+#endif
 			cpu_sys_dev = get_cpu_sysdev(j);
 			sysfs_remove_link(&cpu_sys_dev->kobj, "cpufreq");
 			cpufreq_cpu_put(data);