EVENTFD_MAXVAL
if (write_value > EVENTFD_MAXVAL) {
KASSERT(efd->efd_val <= EVENTFD_MAXVAL);
while ((EVENTFD_MAXVAL - efd->efd_val) < write_value) {
KASSERT(efd->efd_val <= EVENTFD_MAXVAL);
if (efd->efd_val < EVENTFD_MAXVAL) {
rv = (eventfd_t)kn->kn_data < EVENTFD_MAXVAL;