1 files changed, 20 insertions, 11 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c29831076e7a..e14db9c089b9 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1115,8 +1115,10 @@ static void cgroup_kill_sb(struct super_block *sb) {
         }
         write_unlock(&css_set_lock);
 
-        list_del(&root->root_list);
-        root_count--;
+        if (!list_empty(&root->root_list)) {
+                list_del(&root->root_list);
+                root_count--;
+        }
 
         mutex_unlock(&cgroup_mutex);
 
@@ -2349,7 +2351,7 @@ static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
         for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                 struct cgroup_subsys *ss = subsys[i];
                 if (ss->root == root)
-                        mutex_lock_nested(&ss->hierarchy_mutex, i);
+                        mutex_lock(&ss->hierarchy_mutex);
         }
 }
 
@@ -2434,7 +2436,9 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
  err_remove:
 
+        cgroup_lock_hierarchy(root);
         list_del(&cgrp->sibling);
+        cgroup_unlock_hierarchy(root);
         root->number_of_cgroups--;
 
  err_destroy:
@@ -2507,7 +2511,7 @@ static int cgroup_clear_css_refs(struct cgroup *cgrp)
         for_each_subsys(cgrp->root, ss) {
                 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
                 int refcnt;
-                do {
+                while (1) {
                         /* We can only remove a CSS with a refcnt==1 */
                         refcnt = atomic_read(&css->refcnt);
                         if (refcnt > 1) {
@@ -2521,7 +2525,10 @@ static int cgroup_clear_css_refs(struct cgroup *cgrp)
                          * css_tryget() to spin until we set the
                          * CSS_REMOVED bits or abort
                          */
-                } while (atomic_cmpxchg(&css->refcnt, refcnt, 0) != refcnt);
+                        if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
+                                break;
+                        cpu_relax();
+                }
         }
  done:
         for_each_subsys(cgrp->root, ss) {
@@ -2630,6 +2637,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
         BUG_ON(!list_empty(&init_task.tasks));
 
         mutex_init(&ss->hierarchy_mutex);
+        lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
         ss->active = 1;
 }
 
@@ -2991,20 +2999,21 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
                 mutex_unlock(&cgroup_mutex);
                 return 0;
         }
-        task_lock(tsk);
-        cg = tsk->cgroups;
-        parent = task_cgroup(tsk, subsys->subsys_id);
 
         /* Pin the hierarchy */
-        if (!atomic_inc_not_zero(&parent->root->sb->s_active)) {
+        if (!atomic_inc_not_zero(&root->sb->s_active)) {
                 /* We race with the final deactivate_super() */
                 mutex_unlock(&cgroup_mutex);
                 return 0;
         }
 
         /* Keep the cgroup alive */
+        task_lock(tsk);
+        parent = task_cgroup(tsk, subsys->subsys_id);
+        cg = tsk->cgroups;
         get_css_set(cg);
         task_unlock(tsk);
+
         mutex_unlock(&cgroup_mutex);
 
         /* Now do the VFS work to create a cgroup */
@@ -3043,7 +3052,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
                 mutex_unlock(&inode->i_mutex);
                 put_css_set(cg);
 
-                deactivate_super(parent->root->sb);
+                deactivate_super(root->sb);
                 /* The cgroup is still accessible in the VFS, but
                  * we're not going to try to rmdir() it at this
                  * point. */
@@ -3069,7 +3078,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
         mutex_lock(&cgroup_mutex);
         put_css_set(cg);
         mutex_unlock(&cgroup_mutex);
-        deactivate_super(parent->root->sb);
+        deactivate_super(root->sb);
         return ret;
 }