On Tue, 16 Jun 2020 12:48:58 +0200, Martin Pieuchot wrote: > The diff below implements DragonFly's approach of adding a new kind of > filter, EVFILT_EXCEPT, to report such conditions. This extends the > existing kqueue interface which is questionable. On the one hand this > allows userland programs to use kevent(2) to check for this conditions. > One the other hand this is not supported by any other BSD and thus non > standard.
Actually, it looks like macOS uses EVFILT_EXCEPT too. They were the first OS to implement poll in terms of kqueue as far as I know. I don't think there is a problem extended kqueue with EVFILT_EXCEPT. > In the tree there's two poll handlers that set the POLLPRI & POLLRDBAND > bits as illustrated by the diff below. > > Do we see value in this new type of filter? Should I document it and > put it in? Or should I restrict it to the __EV_POLL for now? In the > latter case should we pick a different name and/or prefix it? I think EVFILT_EXCEPT should be exposed to userland. It is not our own invention and two other OSes support it. OK millert@ - todd
