+ /*
+ * css_put/get is provided for subsys to grab refcnt to css. In typical
+ * case, subsystem has no reference after pre_destroy(). But, under
+ * hierarchy management, some *temporal* refcnt can be hold.
+ * To avoid returning -EBUSY to a user, waitqueue is used. If subsys
+ * is really busy, it should return -EBUSY at pre_destroy(). wake_up
+ * is called when css_put() is called and refcnt goes down to 0.
+ */
+ set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
+ prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
+
+ if (!cgroup_clear_css_refs(cgrp)) {
+ mutex_unlock(&cgroup_mutex);
+ schedule();
+ finish_wait(&cgroup_rmdir_waitq, &wait);
+ clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
+ if (signal_pending(current))
+ return -EINTR;
+ goto again;
+ }
+ /* NO css_tryget() can success after here. */
+ finish_wait(&cgroup_rmdir_waitq, &wait);
+ clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);