NEXT_IN
ep = NEXT_IN(ep);
lock->l_sedge = NEXT_IN(ep);
for (ep = FIRST_IN(request); ep != HEAD(request); ep = NEXT_IN(ep)) {
lock->l_sedge = NEXT_IN(ep);
vertex->l_sedge = NEXT_IN(ep);
ep = NEXT_IN(ep)) {
ep = NEXT_IN(ep)) {
ep = NEXT_IN(ep);
nep = NEXT_IN(ep);
ep = NEXT_IN(ep);