Re: [Libguestfs] [libnbd PATCH] rust: Use mio::poll instead of requiring epoll

On Mon, Sep 04, 2023 at 06:59:15PM +0000, Tage Johansson wrote: > > > > + // can be both readable and writable, but we survive just fine > > > + // if we only see one direction even when both are available. > > > + poll.registry().register( > > > + &mut SourceFd(&fd), > > > + Token(0), > > > + MioInterest::READABLE | MioInterest::WRITABLE, > > > + )?; > > > + poll.poll(&mut events, Some(Duration::ZERO))?; > > Why do we want 'poll.poll()?;', that is, to fail this function if the > > poll returns an error? We _expect_ poll to sometimes return an error > > (namely, the fact that it timed out) if there is nothing pending on > > the fd, at which point we WANT to successfully clear the ready_guard > > for both read and write, rather than to error out of this function. > > > You are right. I thought that the poll() call would return Ok(()) upon > timeout, but according to the documentation: > > > Currently if the timeout elapses without any readiness events triggering > > this will return Ok(()). However we’re not guaranteeing this behaviour > > as this depends on the OS. > > So I guess it is best to ignore any errors from the poll call as in your > patch. Okay, I'll merge in that aspect of my original along with your other improvements, and push something soon. Fingers crossed that we'll finally get a green CI run today.