txbr_windex
windex = atomic_load_acq_32(&tbr->txbr_windex);
old_windex = tbr->txbr_windex;
atomic_store_rel_32(&tbr->txbr_windex, windex);
old_windex = atomic_load_acq_32(&tbr->txbr_windex);
atomic_store_rel_32(&tbr->txbr_windex, windex);
return (atomic_load_acq_32(&tbr->txbr_windex) ==