cgroup: cgroup_subsys->fork() should be called after the task is added to css_set

[pandora-kernel.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6337535..a51ba74 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4507,42 +4507,20 @@ void cgroup_fork(struct task_struct *child)
        INIT_LIST_HEAD(&child->cg_list);
 }
 
-/**
- * cgroup_fork_callbacks - run fork callbacks
- * @child: the new task
- *
- * Called on a new task very soon before adding it to the
- * tasklist. No need to take any locks since no-one can
- * be operating on this task.
- */
-void cgroup_fork_callbacks(struct task_struct *child)
-{
-       if (need_forkexit_callback) {
-               int i;
-               /*
-                * forkexit callbacks are only supported for builtin
-                * subsystems, and the builtin section of the subsys array is
-                * immutable, so we don't need to lock the subsys array here.
-                */
-               for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
-                       struct cgroup_subsys *ss = subsys[i];
-                       if (ss->fork)
-                               ss->fork(ss, child);
-               }
-       }
-}
-
 /**
  * cgroup_post_fork - called on a new task after adding it to the task list
  * @child: the task in question
  *
- * Adds the task to the list running through its css_set if necessary.
- * Has to be after the task is visible on the task list in case we race
- * with the first call to cgroup_iter_start() - to guarantee that the
- * new task ends up on its list.
+ * Adds the task to the list running through its css_set if necessary and
+ * call the subsystem fork() callbacks.  Has to be after the task is
+ * visible on the task list in case we race with the first call to
+ * cgroup_iter_start() - to guarantee that the new task ends up on its
+ * list.
  */
 void cgroup_post_fork(struct task_struct *child)
 {
+       int i;
+
        if (use_task_css_set_links) {
                write_lock(&css_set_lock);
                task_lock(child);
@@ -4551,7 +4529,21 @@ void cgroup_post_fork(struct task_struct *child)
                task_unlock(child);
                write_unlock(&css_set_lock);
        }
+
+       /*
+        * Call ss->fork().  This must happen after @child is linked on
+        * css_set; otherwise, @child might change state between ->fork()
+        * and addition to css_set.
+        */
+       if (need_forkexit_callback) {
+               for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+                       struct cgroup_subsys *ss = subsys[i];
+                       if (ss->fork)
+                               ss->fork(ss, child);
+               }
+       }
 }
+
 /**
  * cgroup_exit - detach cgroup from exiting task
  * @tsk: pointer to task_struct of exiting process