BT_TYPE_BUSY
btnew->bt_type = BT_TYPE_BUSY;
bt->bt_type = BT_TYPE_BUSY;
btnew->bt_type = BT_TYPE_BUSY;
if (bt->bt_type == BT_TYPE_BUSY)
KASSERT(bt->bt_type == BT_TYPE_BUSY);
KASSERT(BT_ISSPAN_P(t) || t->bt_type == BT_TYPE_BUSY);
[BT_TYPE_BUSY] = "busy",
(bt->bt_type == BT_TYPE_BUSY) ? "allocated" : "free");
KASSERT(bt->bt_type == BT_TYPE_BUSY);