ZSD_DESTROY_NEEDED
if (t->zsd_flags & ZSD_DESTROY_NEEDED) {
t->zsd_flags &= ~ZSD_DESTROY_NEEDED;
del->zsd_flags |= ZSD_DESTROY_NEEDED;
t->zsd_flags |= ZSD_DESTROY_NEEDED;
(ZSD_DESTROY_NEEDED|ZSD_DESTROY_INPROGRESS|ZSD_DESTROY_COMPLETED)