When is called `select`, but registered no one `fileobject` rise exception:
...
    polled = self._selector.select(timeout)
  File "/usr/lib/python3.4/selectors.py", line 424, in select
    fd_event_list = self._epoll.poll(timeout, max_ev)
ValueError: maxevents must be greater than 0, got 0

Of course, it makes no sense to call `select` if there is nothing to watch. But "select.epol.poll" is not raises exception in the same case if `max_ev`=-1. And this simplifies the application code and is useful if need just sleep for a timeout.

So, I suggest a small fix:
-    fd_event_list = self._epoll.poll(timeout, max_ev)
+    fd_event_list = self._epoll.poll(timeout, max_ev or -1)

Patch attached. Tests pass on Linux.

+        s.select(timeout=0)

I suggest to ensure that the result is an empty list.

I agree. Please see another one.

It's a little bit surprising to call epoll_wait() without any FD subscribed, but select([], [], [], delay) is a known way to sleep 'delay' seconds, so why not using epoll in a similar way? :-)

epoll_02.patch looks good to me. Can you please also apply the patch to the Tulip project?

(By the way, test_selectors.py to Tulip is completly different, we may just reuse the file from CPython and drop the code from Tulip.)

Please add a comment explaining the complaint from epoll.poll() we're
trying to avoid here.

I presume Tulip never gets into this state because of the self-pipe.

On Mon, Dec 8, 2014 at 8:01 AM, STINNER Victor <report@bugs.python.org>
wrote:

>
> STINNER Victor added the comment:
>
> It's a little bit surprising to call epoll_wait() without any FD
> subscribed, but select([], [], [], delay) is a known way to sleep 'delay'
> seconds, so why not using epoll in a similar way? :-)
>
> epoll_02.patch looks good to me. Can you please also apply the patch to
> the Tulip project?
>
> (By the way, test_selectors.py to Tulip is completly different, we may
> just reuse the file from CPython and drop the code from Tulip.)
>
> ----------
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue23009>
> _______________________________________
>

New changeset b2ee06684b6a by Yury Selivanov in branch '3.4':
selectors: Make sure EpollSelecrtor.select() works when no FD is registered.
https://hg.python.org/cpython/rev/b2ee06684b6a

New changeset 202995833ef4 by Yury Selivanov in branch 'default':
selectors: Make sure EpollSelecrtor.select() works when no FD is registered.
https://hg.python.org/cpython/rev/202995833ef4

> Please add a comment explaining the complaint from epoll.poll() we're
trying to avoid here.

Good point! Committed.

Thanks for taking care of this.

New changeset 8f1be68dfcab by Yury Selivanov in branch '3.4':
NEWS: Add news entry for issue #23009.
https://hg.python.org/cpython/rev/8f1be68dfcab

New changeset d36711410f48 by Yury Selivanov in branch 'default':
NEWS: Add news entry for issue #23009.
https://hg.python.org/cpython/rev/d36711410f48

New changeset 1e985daa7be6 by Victor Stinner in branch 'default':
Issue #23009: Skip test_selectors.test_empty_select() on Windows
https://hg.python.org/cpython/rev/1e985daa7be6

New changeset d3a27a27e008 by Victor Stinner in branch '3.4':
Issue #23009: Skip test_selectors.test_empty_select() on Windows
https://hg.python.org/cpython/rev/d3a27a27e008

New changeset 4f928c70f135 by Victor Stinner in branch '3.4':
Issue #23009: Add missing "import sys" in test_selectors
https://hg.python.org/cpython/rev/4f928c70f135