如何在任何事件发生之前唤醒epoll_wait（）？

Question

I have a Connection object that represents a connection managed by epoll . On events, the Connection::eventWrite() or Connection::eventRead() are invoked. Connection is persistent (exists always).

I need to send data via that Connection from another thread, but don't want to access the object Connection directly, because I dont want to solve multithreading issues inside the Connection object ( Connection is accessed from epoll -thread and from "sending thread"). Instead, I want to tell epoll -thread: "wake up and do something with Connection " -- epoll_wait() should return and my code will find out that a CUSTOM EVENT is occured (and, for example, some function should be called, where the desired access to Connection will be performed (assign sending data to object, calling writeEvent() ), then epoll_wait() -loop will be continued.

What kind of solutions exists for waking up a epoll_wait() and which one is faster? For now, I came up with creating a pipe (handled by the same epoll ) and writing a byte 1 to it. What else IPC exists which can be expressed via int "epollable" file descriptor?

Answer 1

Epoll can wait on eventfd . In your case, I'd create an eventfd and than trigger this event. I think, this is the cleanest solution.