Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: create rcu_my_thread_group_empty() wrapper
  memcg: css_id() must be called under rcu_read_lock()
  cgroup: Check task_lock in task_subsys_state()
  sched: Fix an RCU warning in print_task()
  cgroup: Fix an RCU warning in alloc_css_id()
  cgroup: Fix an RCU warning in cgroup_path()
  KEYS: Fix an RCU warning in the reading of user keys
  KEYS: Fix an RCU warning

1 files changed, 11 insertions, 5 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e2769e13980c..3a53c771e503 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1646,7 +1646,9 @@ static inline struct cftype *__d_cft(struct dentry *dentry)
 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 {
         char *start;
-        struct dentry *dentry = rcu_dereference(cgrp->dentry);
+        struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
+                                                      rcu_read_lock_held() ||
+                                                      cgroup_lock_is_held());
 
         if (!dentry || cgrp == dummytop) {
                 /*
@@ -1662,13 +1664,17 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
         *--start = '\0';
         for (;;) {
                 int len = dentry->d_name.len;
+
                 if ((start -= len) < buf)
                         return -ENAMETOOLONG;
-                memcpy(start, cgrp->dentry->d_name.name, len);
+                memcpy(start, dentry->d_name.name, len);
                 cgrp = cgrp->parent;
                 if (!cgrp)
                         break;
-                dentry = rcu_dereference(cgrp->dentry);
+
+                dentry = rcu_dereference_check(cgrp->dentry,
+                                               rcu_read_lock_held() ||
+                                               cgroup_lock_is_held());
                 if (!cgrp->parent)
                         continue;
                 if (--start < buf)
@@ -4555,13 +4561,13 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
 {
         int subsys_id, i, depth = 0;
         struct cgroup_subsys_state *parent_css, *child_css;
-        struct css_id *child_id, *parent_id = NULL;
+        struct css_id *child_id, *parent_id;
 
         subsys_id = ss->subsys_id;
         parent_css = parent->subsys[subsys_id];
         child_css = child->subsys[subsys_id];
-        depth = css_depth(parent_css) + 1;
         parent_id = parent_css->id;
+        depth = parent_id->depth;
 
         child_id = get_new_cssid(ss, depth);
         if (IS_ERR(child_id))