1 files changed, 17 insertions, 27 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 2011ad8d2697..c77bc3a1c722 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -33,17 +33,13 @@ static struct {
          * an ongoing cpu hotplug operation.
          */
         int refcount;
-        wait_queue_head_t writer_queue;
 } cpu_hotplug;
 
-#define writer_exists() (cpu_hotplug.active_writer != NULL)
-
 void __init cpu_hotplug_init(void)
 {
         cpu_hotplug.active_writer = NULL;
         mutex_init(&cpu_hotplug.lock);
         cpu_hotplug.refcount = 0;
-        init_waitqueue_head(&cpu_hotplug.writer_queue);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -65,11 +61,8 @@ void put_online_cpus(void)
         if (cpu_hotplug.active_writer == current)
                 return;
         mutex_lock(&cpu_hotplug.lock);
-        cpu_hotplug.refcount--;
-
-        if (unlikely(writer_exists()) && !cpu_hotplug.refcount)
-                wake_up(&cpu_hotplug.writer_queue);
-
+        if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
+                wake_up_process(cpu_hotplug.active_writer);
         mutex_unlock(&cpu_hotplug.lock);
 
 }
@@ -98,8 +91,8 @@ void cpu_maps_update_done(void)
  * Note that during a cpu-hotplug operation, the new readers, if any,
  * will be blocked by the cpu_hotplug.lock
  *
- * Since cpu_maps_update_begin is always called after invoking
- * cpu_maps_update_begin, we can be sure that only one writer is active.
+ * Since cpu_hotplug_begin() is always called after invoking
+ * cpu_maps_update_begin(), we can be sure that only one writer is active.
  *
  * Note that theoretically, there is a possibility of a livelock:
  * - Refcount goes to zero, last reader wakes up the sleeping
@@ -115,19 +108,16 @@ void cpu_maps_update_done(void)
  */
 static void cpu_hotplug_begin(void)
 {
-        DECLARE_WAITQUEUE(wait, current);
-
-        mutex_lock(&cpu_hotplug.lock);
-
         cpu_hotplug.active_writer = current;
-        add_wait_queue_exclusive(&cpu_hotplug.writer_queue, &wait);
-        while (cpu_hotplug.refcount) {
-                set_current_state(TASK_UNINTERRUPTIBLE);
+
+        for (;;) {
+                mutex_lock(&cpu_hotplug.lock);
+                if (likely(!cpu_hotplug.refcount))
+                        break;
+                __set_current_state(TASK_UNINTERRUPTIBLE);
                 mutex_unlock(&cpu_hotplug.lock);
                 schedule();
-                mutex_lock(&cpu_hotplug.lock);
         }
-        remove_wait_queue_locked(&cpu_hotplug.writer_queue, &wait);
 }
 
 static void cpu_hotplug_done(void)
@@ -136,7 +126,7 @@ static void cpu_hotplug_done(void)
         mutex_unlock(&cpu_hotplug.lock);
 }
 /* Need to know about CPUs going up/down? */
-int __cpuinit register_cpu_notifier(struct notifier_block *nb)
+int __ref register_cpu_notifier(struct notifier_block *nb)
 {
         int ret;
         cpu_maps_update_begin();
@@ -149,7 +139,7 @@ int __cpuinit register_cpu_notifier(struct notifier_block *nb)
 
 EXPORT_SYMBOL(register_cpu_notifier);
 
-void unregister_cpu_notifier(struct notifier_block *nb)
+void __ref unregister_cpu_notifier(struct notifier_block *nb)
 {
         cpu_maps_update_begin();
         raw_notifier_chain_unregister(&cpu_chain, nb);
@@ -180,7 +170,7 @@ struct take_cpu_down_param {
 };
 
 /* Take this CPU down. */
-static int take_cpu_down(void *_param)
+static int __ref take_cpu_down(void *_param)
 {
         struct take_cpu_down_param *param = _param;
         int err;
@@ -199,7 +189,7 @@ static int take_cpu_down(void *_param)
 }
 
 /* Requires cpu_add_remove_lock to be held */
-static int _cpu_down(unsigned int cpu, int tasks_frozen)
+static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 {
         int err, nr_calls = 0;
         struct task_struct *p;
@@ -225,7 +215,7 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
                 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
                                           hcpu, nr_calls, NULL);
                 printk("%s: attempt to take down CPU %u failed\n",
-                                __FUNCTION__, cpu);
+                                __func__, cpu);
                 err = -EINVAL;
                 goto out_release;
         }
@@ -274,7 +264,7 @@ out_release:
         return err;
 }
 
-int cpu_down(unsigned int cpu)
+int __ref cpu_down(unsigned int cpu)
 {
         int err = 0;
 
@@ -305,7 +295,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
         if (ret == NOTIFY_BAD) {
                 nr_calls--;
                 printk("%s: attempt to bring up CPU %u failed\n",
-                                __FUNCTION__, cpu);
+                                __func__, cpu);
                 ret = -EINVAL;
                 goto out_notify;
         }