-/* Locks taken and their ordering
- * ------------------------------
- * cgroup_mutex (AKA cgroup_lock)
- * freezer->lock
- * css_set_lock
- * task->alloc_lock (AKA task_lock)
- * task->sighand->siglock
- *
- * cgroup code forces css_set_lock to be taken before task->alloc_lock
- *
- * freezer_create(), freezer_destroy():
- * cgroup_mutex [ by cgroup core ]
- *
- * freezer_can_attach():
- * cgroup_mutex (held by caller of can_attach)
- *
- * freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
- * freezer->lock
- * sighand->siglock (if the cgroup is freezing)
- *
- * freezer_read():
- * cgroup_mutex
- * freezer->lock
- * write_lock css_set_lock (cgroup iterator start)
- * task->alloc_lock
- * read_lock css_set_lock (cgroup iterator start)
- *
- * freezer_write() (freeze):
- * cgroup_mutex
- * freezer->lock
- * write_lock css_set_lock (cgroup iterator start)
- * task->alloc_lock
- * read_lock css_set_lock (cgroup iterator start)
- * sighand->siglock (fake signal delivery inside freeze_task())
- *
- * freezer_write() (unfreeze):
- * cgroup_mutex
- * freezer->lock
- * write_lock css_set_lock (cgroup iterator start)
- * task->alloc_lock
- * read_lock css_set_lock (cgroup iterator start)
- * task->alloc_lock (inside __thaw_task(), prevents race with refrigerator())
- * sighand->siglock
- */
-static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup)