Have you ever tried to think what it means for different *processes*
sharing a single epoll fd and doing epoll_wait() over it?
Most common case is a single event fetch thread plus dispatch. Going to
epoll_wait() over a single epoll fd from many *threads* is very much
possible, but requires care (news at 11, system software development
requires care too).
Sharing a single epoll fd (by the means of any process sharing it doing
add/wait) from different *processes* makes almost no sense at all.
"a child process cannot add the duplicate file descriptor to the epoll
set" ... how do you expect the parent (that doesn't even have the new fd
mapped) to react to such events?
If the next question is "But then why we made the epoll fd inheritable?",
the answer is, because it makes sense in many cases for a parent to hand
over an fd set to a child.
I think we already went over this, and I think I clearly explained you the
reasons of not hooking into sys_close.
- Davide
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