On Sat, 27 Oct 2007, Marc Lehmann wrote:
> > Please provide some code to illustrate one exact problem you have.
>
> // assume there is an open epoll set that listens for events on fd 5
> if (fork () = 0)
> {
> close (5);
> // fd 5 is now removed from the epoll set of the parent.
> _exit (0);
> }
Hmmm ... what? I assume you know that:
1) A file descriptor is a userspace view/handle of a kernel object
2) The kernel object has a use-count for as many file descriptors that
have been handed out to userspace
3) A close() decreases the internal counter by one
4) The kernel object gets effectively closed when the internal counter
goes to zero
5) A fork() acts as a dup() on the file descriptors by hence bumping up
its internal counter
6) Epoll removes the file from the set, when the *kernel* object gets
closed (internal use-count goes to zero)
With that in mind, how can the code snippet above trigger a removal from
the epoll set?
- Davide
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