Prevent using mioco types from multiple thread(coroutines) at the same time.

[dpc]

Reported originally in #122

let mut remote: TcpStream = ...;
let mut origin = try!(TcpStream::connect(&addr));

let mut remote2 = try!(remote.try_clone());
let mut origin2 = try!(origin.try_clone());

mioco::spawn(move || -> io::Result<()> {
    let mut buf = [0; 1024];
    loop {
        let size = try!(remote2.read(&mut buf));
        if size == 0 {
            break;
        }
        origin2.write_all(&buf[..size]);
    }
    Ok(())
});

mioco::spawn(move || -> io::Result<()> {
    let mut buf = [0; 1024];
    loop {
        let size = try!(origin.read(&mut buf));
        if size == 0 {
            break;
        }
        remote.write_all(&buf[..size]);
    }
    Ok(())
});

try_clone must return a deep clone (new fd), or not work at all. Also: make sure mioco types can't be used from multiple threads/coroutines at the same time.

[dpc]

@sbstp: Do you happen to have a full example?

[sbstp]

Unfortunately I don't. I no longer have the code that does this. I rewrote it using select! and it looks much better and uses a single coroutine. What I gave you in the other issue is a partial reconstruction of what it looked like.

[dpc]

I think for whatever reason try_clone did not dup the actual fd. I need to reproduce and investigate more