[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=8671

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 22 insertions, 1 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 99f9c3c23845..2f6a73c01b71 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/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);