Is epoll thread-safe?

Question

There are two functions in epoll:

1. epoll_ctl
2. epoll_wait

Are they thread-safe when I use the same epoll_fd?
What wi

Answer 1

It is thread-safe, but there isn't much documentation that explicitly states that. See here

BTW, you can also have multiple threads waiting on a single epoll_fd, but in that case it can get a bit tricky. (I.e. you might want to use edge-triggered EPOLLET or oneshot mode EPOLLONESHOT. See here.)