EFD_SEMAPHORE
nflags |= EFD_SEMAPHORE;
efd->efd_is_semaphore = !!(flags & EFD_SEMAPHORE);
if (flags & ~(EFD_CLOEXEC | EFD_NONBLOCK | EFD_SEMAPHORE)) {
ATF_REQUIRE((efd = eventfd(3, EFD_SEMAPHORE | EFD_NONBLOCK)) >= 0);
eventfd(0, ~(EFD_SEMAPHORE | EFD_CLOEXEC | EFD_NONBLOCK)) == -1);