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;