Epoll_wait() receives socket closed twice (read()/recv() returns 0)?

As soon as the first read() returns 0, this means that the connection was closed by the peer. Why does the kernel generate a EPOLLIN event for this case? Well, there's no other way to indicate the socket's closure when you're only subscribed to EPOLLIN.

You can add EPOLLRDHUP which is basically the same as checking for read() returning 0. However, make sure to test for this flag before you test for EPOLLIN.

Assuming that EPOLLONESHOT is bug free (I haven't searched for associated bugs though), the fact that you are processing your epoll events in another thread and that it crashes sporadically or under heavy load may mean that there is a race condition somewhere in your application.

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