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

> > + // 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.