I think this should this be changed so that epoll passes a pointer in its extra data instead of a file descriptor.

The disadvantages:

It probably requires items to become an array of references to selectitems instead of a value array. It would require some care to ensure some of the value assignments (e.g, si = item) still worked correctly.

The advantages:

it would clean up some of the code/remove the need for the epfdtbl table - and no need to rebuild it.
It might be more efficient having an array of references instead of a value array.
I think it would allow items to be added/deleted without exiting the epoll_wait call.