dt_list_prev
for (dhp = dt_list_prev(&sp->dids_list);
dhp != NULL; dhp = dt_list_prev(dhp)) {
assert(dt_list_prev(&sp->dids_list) == dhp);
for (opr = dt_list_prev(&dph->dph_lrulist);
opr != NULL; opr = dt_list_prev(opr)) {