sio_pgrp
pg = sigio->sio_pgrp;
pg = sigio->sio_pgrp;
KASSERT(sigio->sio_pgrp == pg,
sigio->sio_pgrp = pgrp;
PGRP_LOCK(sigio->sio_pgrp);
LIST_FOREACH(p, &sigio->sio_pgrp->pg_members, p_pglist) {
PGRP_UNLOCK(sigio->sio_pgrp);