2 files changed, 27 insertions, 32 deletions

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index c6f6e0839b61..9f3c7e81270a 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -175,6 +175,8 @@ extern struct bus_type cpu_subsys;
 
 extern void get_online_cpus(void);
 extern void put_online_cpus(void);
+extern void cpu_hotplug_disable(void);
+extern void cpu_hotplug_enable(void);
 #define hotcpu_notifier(fn, pri)        cpu_notifier(fn, pri)
 #define register_hotcpu_notifier(nb)    register_cpu_notifier(nb)
 #define unregister_hotcpu_notifier(nb)  unregister_cpu_notifier(nb)
@@ -198,6 +200,8 @@ static inline void cpu_hotplug_driver_unlock(void)
 
 #define get_online_cpus()       do { } while (0)
 #define put_online_cpus()       do { } while (0)
+#define cpu_hotplug_disable()   do { } while (0)
+#define cpu_hotplug_enable()    do { } while (0)
 #define hotcpu_notifier(fn, pri)        do { (void)(fn); } while (0)
 /* These aren't inline functions due to a GCC bug. */
 #define register_hotcpu_notifier(nb)    ({ (void)(nb); 0; })
diff --git a/kernel/cpu.c b/kernel/cpu.c
index b5e4ab2d427e..198a38883e64 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -133,6 +133,27 @@ static void cpu_hotplug_done(void)
         mutex_unlock(&cpu_hotplug.lock);
 }
 
+/*
+ * Wait for currently running CPU hotplug operations to complete (if any) and
+ * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
+ * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
+ * hotplug path before performing hotplug operations. So acquiring that lock
+ * guarantees mutual exclusion from any currently running hotplug operations.
+ */
+void cpu_hotplug_disable(void)
+{
+        cpu_maps_update_begin();
+        cpu_hotplug_disabled = 1;
+        cpu_maps_update_done();
+}
+
+void cpu_hotplug_enable(void)
+{
+        cpu_maps_update_begin();
+        cpu_hotplug_disabled = 0;
+        cpu_maps_update_done();
+}
+
 #else /* #if CONFIG_HOTPLUG_CPU */
 static void cpu_hotplug_begin(void) {}
 static void cpu_hotplug_done(void) {}
@@ -541,36 +562,6 @@ static int __init alloc_frozen_cpus(void)
 core_initcall(alloc_frozen_cpus);
 
 /*
- * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
- * hotplug when tasks are about to be frozen. Also, don't allow the freezer
- * to continue until any currently running CPU hotplug operation gets
- * completed.
- * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
- * 'cpu_add_remove_lock'. And this same lock is also taken by the regular
- * CPU hotplug path and released only after it is complete. Thus, we
- * (and hence the freezer) will block here until any currently running CPU
- * hotplug operation gets completed.
- */
-void cpu_hotplug_disable_before_freeze(void)
-{
-        cpu_maps_update_begin();
-        cpu_hotplug_disabled = 1;
-        cpu_maps_update_done();
-}
-
-
-/*
- * When tasks have been thawed, re-enable regular CPU hotplug (which had been
- * disabled while beginning to freeze tasks).
- */
-void cpu_hotplug_enable_after_thaw(void)
-{
-        cpu_maps_update_begin();
-        cpu_hotplug_disabled = 0;
-        cpu_maps_update_done();
-}
-
-/*
  * When callbacks for CPU hotplug notifications are being executed, we must
  * ensure that the state of the system with respect to the tasks being frozen
  * or not, as reported by the notification, remains unchanged *throughout the
@@ -589,12 +580,12 @@ cpu_hotplug_pm_callback(struct notifier_block *nb,
 
         case PM_SUSPEND_PREPARE:
         case PM_HIBERNATION_PREPARE:
-                cpu_hotplug_disable_before_freeze();
+                cpu_hotplug_disable();
                 break;
 
         case PM_POST_SUSPEND:
         case PM_POST_HIBERNATION:
-                cpu_hotplug_enable_after_thaw();
+                cpu_hotplug_enable();
                 break;
 
         default: