TWS_FREE_Q
tws_q_insert_tail(sc, &sc->reqs[i], TWS_FREE_Q);
r = tws_q_remove_head(sc, TWS_FREE_Q);
tws_q_insert_tail(sc, req, TWS_FREE_Q);
tws_q_insert_tail(sc, req, TWS_FREE_Q);
tws_q_insert_tail(sc, req, TWS_FREE_Q);
tws_q_insert_tail(sc, req, TWS_FREE_Q);