__read_from_tree
err = __read_from_tree(&root, &lock, rem_tree); \
err = __read_from_tree(&root, &lock, rem_tree); \
INSERT_DOUBLE_READ_AND_DEL(__read_from_tree, root, "insert_double_del: 2x read-and-del from tree");
err = __read_from_tree(&root, &lock, rem_tree); \