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