PF_NOSTOP
pty->pt_flags &= ~(PF_WOPEN|PF_STOPPED|PF_NOSTOP);
if (pty->pt_flags & PF_NOSTOP) {
pty->pt_flags &= ~PF_NOSTOP;
pty->pt_flags |= PF_NOSTOP;
pty->pt_flags &= (PF_WOPEN|PF_STOPPED|PF_NOSTOP);