twe_wait_aen
sc->twe_wait_aen = -1;
if (sc->twe_wait_aen == aen) {
sc->twe_wait_aen = -1;
wakeup(&sc->twe_wait_aen);
sc->twe_wait_aen = aen;
lksleep(&sc->twe_wait_aen, &sc->twe_io_lock, 0, "twewaen", hz);
if (sc->twe_wait_aen == -1)
int twe_wait_aen; /* wait-for-aen notification */