rdsvc
mdb_iob_pipe(iobs, rdsvc, wrsvc);
mdb_iob_pipe(mdb_iob_t **iobs, mdb_iobsvc_f *rdsvc, mdb_iobsvc_f *wrsvc)
mdb_io_t *pio = mdb_pipeio_create(rdsvc, wrsvc);
mdb_pipeio_create(mdb_iobsvc_f *rdsvc, mdb_iobsvc_f *wrsvc)
ASSERT(rdsvc != NULL && wrsvc != NULL);
pd->pipe_rdsvc = rdsvc;