Re: POLLRDONCE optimisation for epoll users (was: epoll and half closed TCP connections)

[Jamie Lokier]

Davide Libenzi wrote:
> Ouch, I definitely liked more the POLLHUP thing. It is not linked to epoll
> at all.

POLLRDONCE isn't linked to epoll - it's a valid hint for poll/select too.

It means something different, i.e. you can't write:

> 	if (events & EPOLLRDHUP) {
> 		d->flags |= HANGUP;
> 		schedule_removal(d);
> 	}

Be careful, because that isn't valid if there is urgent data.  You
need to check POLLPRI too.  Granted urgent data is usually best ignored :)

If fast hangup is a useful optimisation too, we should have both flags.
(However calling read() doesn't seem like a great penalty for that).

-- Jamie