Interrupting epoll_wait with a non-IO event, no signals

Question

Current scenario is epoll_wait over a couple of fds and a queue of possible incoming messages, I\'d like the loop below epoll_wait to be executed on IO event or on new messa

Answer 1

You have enumerated the events that can wake up epoll, so the question really becomes: "How do I reduce the boilerplate for the self-pipe trick?"

The answer to that question really depends on your code, the language and what you are trying to do. I assume you have a thread that processes I/O and you want to do other work in that thread while there is no I/O ready. In the code that manages the epoll loop, it can have an internal handle that is exposed to other parts of the system as a "wake" function or a "submit work" function.

There are libraries that do this, for example boost.asio for C++. However, it isn't difficult to write your own if you're just targeting epoll, and the amount of actual boilerplate code should be minimal once you have a class/module/whatever that deals with the epoll loop.

Answer 2

You can use an eventfd which is effectively the same thing as the self-pipe trick except with fewer file descriptors and less boilerplate (glibc has convenience eventfd_read/write functions for instance).