1 files changed, 8 insertions, 15 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index e345d8b90046..b7bd4beae294 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -20,6 +20,7 @@
 #include <linux/workqueue.h>
 #include <linux/xattr.h>
 #include <linux/fs.h>
+#include <linux/percpu-refcount.h>
 
 #ifdef CONFIG_CGROUPS
 
@@ -72,13 +73,8 @@ struct cgroup_subsys_state {
 	 */
 	struct cgroup *cgroup;
 
-	/*
-	 * State maintained by the cgroup system to allow subsystems
-	 * to be "busy". Should be accessed via css_get(),
-	 * css_tryget() and css_put().
-	 */
-
-	atomic_t refcnt;
+	/* reference count - access via css_[try]get() and css_put() */
+	struct percpu_ref refcnt;
 
 	unsigned long flags;
 	/* ID for this css, if possible */
@@ -104,11 +100,9 @@ static inline void css_get(struct cgroup_subsys_state *css)
 {
 	/* We don't need to reference count the root state */
 	if (!(css->flags & CSS_ROOT))
-		atomic_inc(&css->refcnt);
+		percpu_ref_get(&css->refcnt);
 }
 
-extern bool __css_tryget(struct cgroup_subsys_state *css);
-
 /**
  * css_tryget - try to obtain a reference on the specified css
  * @css: target css
@@ -123,11 +117,9 @@ static inline bool css_tryget(struct cgroup_subsys_state *css)
 {
 	if (css->flags & CSS_ROOT)
 		return true;
-	return __css_tryget(css);
+	return percpu_ref_tryget(&css->refcnt);
 }
 
-extern void __css_put(struct cgroup_subsys_state *css);
-
 /**
  * css_put - put a css reference
  * @css: target css
@@ -137,7 +129,7 @@ extern void __css_put(struct cgroup_subsys_state *css);
 static inline void css_put(struct cgroup_subsys_state *css)
 {
 	if (!(css->flags & CSS_ROOT))
-		__css_put(css);
+		percpu_ref_put(&css->refcnt);
 }
 
 /* bits in struct cgroup flags field */
@@ -231,9 +223,10 @@ struct cgroup {
 	struct list_head pidlists;
 	struct mutex pidlist_mutex;
 
-	/* For RCU-protected deletion */
+	/* For css percpu_ref killing and RCU-protected deletion */
 	struct rcu_head rcu_head;
 	struct work_struct destroy_work;
+	atomic_t css_kill_cnt;
 
 	/* List of events which userspace want to receive */
 	struct list_head event_list;