Merge branch 'master' into for-linus

1 files changed, 14 insertions, 6 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 0c621604baa1..e3d00fdb858d 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -525,13 +525,21 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state(
         return cgrp->subsys[subsys_id];
 }
 
-static inline struct cgroup_subsys_state *task_subsys_state(
-        struct task_struct *task, int subsys_id)
+/*
+ * function to get the cgroup_subsys_state which allows for extra
+ * rcu_dereference_check() conditions, such as locks used during the
+ * cgroup_subsys::attach() methods.
+ */
+#define task_subsys_state_check(task, subsys_id, __c)                   \
+        rcu_dereference_check(task->cgroups->subsys[subsys_id],         \
+                              rcu_read_lock_held() ||                   \
+                              lockdep_is_held(&task->alloc_lock) ||     \
+                              cgroup_lock_is_held() || (__c))
+
+static inline struct cgroup_subsys_state *
+task_subsys_state(struct task_struct *task, int subsys_id)
 {
-        return rcu_dereference_check(task->cgroups->subsys[subsys_id],
-                                     rcu_read_lock_held() ||
-                                     lockdep_is_held(&task->alloc_lock) ||
-                                     cgroup_lock_is_held());
+        return task_subsys_state_check(task, subsys_id, false);
 }
 
 static inline struct cgroup* task_cgroup(struct task_struct *task,