TDP_RFPPWAIT
ast_register(TDA_VFORK, ASTR_ASTF_REQUIRED | ASTR_TDP, TDP_RFPPWAIT,
td->td_pflags |= TDP_RFPPWAIT;
MPASS(td->td_pflags & TDP_RFPPWAIT);
td->td_pflags &= ~TDP_RFPPWAIT;