following the discussion at How do you use AIO and epoll together in a single event loop?.
There are in fact 2 "aio" APIs in linux. There's POSIX aio (the aio_* family of functions), included in glibc and libaio developed I believe by RedHat (?), the io_* family.
The first one allows registration of notification requests via aio_sigevent aiocb member. That can be easily integrated with ppoll()/pselect() event loops. If you want to integrate POSIX aio with epoll() then you need to translate the signal into an event on a dummy fd (a pipe maybe) and listen for it with epoll, while catching the signal either in a classic manner or with ppoll/select. How safe is the first choice (normal sighandlers), depends on application. And maybe on epoll but i'm not fully aware of its internals. May I safely assume that if I have an epoll based app and I want to add POSIX aio support then I'm screwed? This was my question.
The second AIO implementation, libaio - can be used indeed with eventfd() (struct iocb having an aio_resfd member that is expected to be zero or an eventfd to deliver AIO results to). But it's not by the book. POSIX-specified, that is.
I dream of myself being a *BSD user where everything is clear. You have the POSIX AIO and kqueue() support for AIO events. Crystal clear. Like many other things.