EFD_NONBLOCK
fds [1] = eventfd (0, EFD_NONBLOCK | EFD_CLOEXEC);
# ifndef EFD_NONBLOCK
ctx->event = eventfd(0, EFD_NONBLOCK);
flags |= EFD_NONBLOCK;
if ((flags & EFD_NONBLOCK) != 0)
_Static_assert(EFD_NONBLOCK == O_NONBLOCK, "Mismatched EFD_NONBLOCK");
if ((ae.flags & ~(EFD_CLOEXEC | EFD_NONBLOCK |