HW_RUNNING
running = (sc->sc_flags & HW_RUNNING) ? 1: 0;
sc->sc_flags &= ~HW_RUNNING;
!(sc->sc_flags & HW_RUNNING))
if (__predict_false(sc->sc_flags & HW_RUNNING)) {
sc->sc_flags |= HW_RUNNING; /* dropped by intr or timeout */
sc->sc_flags &= ~HW_RUNNING;