1 files changed, 64 insertions, 5 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 346906a96e8b..6c6121b85a54 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -4,6 +4,9 @@
  *  Copyright (C) 2001 Russell King
  *            (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>
  *
+ *  Oct 2005 - Ashok Raj <ashok.raj@intel.com>
+ *                      Added handling for CPU hotplug
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
@@ -567,6 +570,9 @@ static int cpufreq_add_dev (struct sys_device * sys_dev)
         unsigned long flags;
         unsigned int j;
 
+        if (cpu_is_offline(cpu))
+                return 0;
+
         cpufreq_debug_disable_ratelimit();
         dprintk("adding CPU %u\n", cpu);
 
@@ -673,7 +679,7 @@ err_out:
 
 nomem_out:
         module_put(cpufreq_driver->owner);
- module_out:
+module_out:
         cpufreq_debug_enable_ratelimit();
         return ret;
 }
@@ -762,7 +768,6 @@ static int cpufreq_remove_dev (struct sys_device * sys_dev)
         down(&data->lock);
         if (cpufreq_driver->target)
                 __cpufreq_governor(data, CPUFREQ_GOV_STOP);
-        cpufreq_driver->target = NULL;
         up(&data->lock);
 
         kobject_unregister(&data->kobj);
@@ -1109,17 +1114,30 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
                             unsigned int relation)
 {
         int retval = -EINVAL;
-        lock_cpu_hotplug();
+
+        /*
+         * Converted the lock_cpu_hotplug to preempt_disable()
+         * and preempt_enable(). This is a bit kludgy and relies on how cpu
+         * hotplug works. All we need is a guarantee that cpu hotplug won't make
+         * progress on any cpu. Once we do preempt_disable(), this would ensure
+         * that hotplug threads don't get onto this cpu, thereby delaying
+         * the cpu remove process.
+         *
+         * We removed the lock_cpu_hotplug since we need to call this function
+         * via cpu hotplug callbacks, which result in locking the cpu hotplug
+         * thread itself. Agree this is not very clean, cpufreq community
+         * could improve this if required. - Ashok Raj <ashok.raj@intel.com>
+         */
+        preempt_disable();
         dprintk("target for CPU %u: %u kHz, relation %u\n", policy->cpu,
                 target_freq, relation);
         if (cpu_online(policy->cpu) && cpufreq_driver->target)
                 retval = cpufreq_driver->target(policy, target_freq, relation);
-        unlock_cpu_hotplug();
+        preempt_enable();
         return retval;
 }
 EXPORT_SYMBOL_GPL(__cpufreq_driver_target);
 
-
 int cpufreq_driver_target(struct cpufreq_policy *policy,
                           unsigned int target_freq,
                           unsigned int relation)
@@ -1406,6 +1424,45 @@ int cpufreq_update_policy(unsigned int cpu)
 }
 EXPORT_SYMBOL(cpufreq_update_policy);
 
+static int __cpuinit cpufreq_cpu_callback(struct notifier_block *nfb,
+                                        unsigned long action, void *hcpu)
+{
+        unsigned int cpu = (unsigned long)hcpu;
+        struct cpufreq_policy *policy;
+        struct sys_device *sys_dev;
+
+        sys_dev = get_cpu_sysdev(cpu);
+
+        if (sys_dev) {
+                switch (action) {
+                case CPU_ONLINE:
+                        cpufreq_add_dev(sys_dev);
+                        break;
+                case CPU_DOWN_PREPARE:
+                        /*
+                         * We attempt to put this cpu in lowest frequency
+                         * possible before going down. This will permit
+                         * hardware-managed P-State to switch other related
+                         * threads to min or higher speeds if possible.
+                         */
+                        policy = cpufreq_cpu_data[cpu];
+                        if (policy) {
+                                cpufreq_driver_target(policy, policy->min,
+                                                CPUFREQ_RELATION_H);
+                        }
+                        break;
+                case CPU_DEAD:
+                        cpufreq_remove_dev(sys_dev);
+                        break;
+                }
+        }
+        return NOTIFY_OK;
+}
+
+static struct notifier_block cpufreq_cpu_notifier =
+{
+    .notifier_call = cpufreq_cpu_callback,
+};
 
 /*********************************************************************
  *               REGISTER / UNREGISTER CPUFREQ DRIVER                *
@@ -1466,6 +1523,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
         }
 
         if (!ret) {
+                register_cpu_notifier(&cpufreq_cpu_notifier);
                 dprintk("driver %s up and running\n", driver_data->name);
                 cpufreq_debug_enable_ratelimit();
         }
@@ -1497,6 +1555,7 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
         dprintk("unregistering driver %s\n", driver->name);
 
         sysdev_driver_unregister(&cpu_sysdev_class, &cpufreq_sysdev_driver);
+        unregister_cpu_notifier(&cpufreq_cpu_notifier);
 
         spin_lock_irqsave(&cpufreq_driver_lock, flags);
         cpufreq_driver = NULL;