leaf_walk_rcu
while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
while ((l = leaf_walk_rcu(tp, key)) && (pos-- > 0)) {
l = leaf_walk_rcu(&iter->tnode, key);