kn_udata
p->p_kq_serial > (unsigned long)kn->kn_udata) {
p->p_kq_serial > (unsigned long)kn->kn_udata) &&
kn->kn_udata = kev->udata;
kev.udata = kn->kn_udata; /* preserve udata */
kn->kn_udata = kev->udata;