Waking up Tokio Blocking Thread attempt

gistfile1.rs

#![feature(async_await)]

use std::error::Error;
use tokio::spawn;
use tokio::prelude::*;
use tokio::future::poll_fn;
use tokio_threadpool::blocking;
use tokio::sync::oneshot::{Sender, Receiver, channel};

#[tokio::main]
async fn main() {
    let (init_tx, mut init_rx) = channel::<(usize, Sender<bool>)>();

    spawn(async move {
        poll_fn(|_| blocking(|| {
            let f = async {
                println!("In thread");

                // A point of failure
                let (x, done_tx) = init_rx.try_recv().unwrap();

                println!("X received: {}", x);

                done_tx.send(true);
            };

            tokio_executor::enter().unwrap().block_on(f);

        })).await;
    });

    // Removing this line makes code work
    std::thread::sleep(std::time::Duration::from_secs(5));

    println!("Before init");

    let (done_tx, done_rx) = channel();

    init_tx.send((100, done_tx)).map_err(|_| panic!("Failed to send"));

    println!("After init");

    done_rx.await;
}

An error:

thread 'tokio-runtime-worker-0' panicked at 'called `Result::unwrap()` on an `Err` value: EnterError { reason: "attempted to run an executor while another executor is already running" }', src/libcore/result.rs:1084:5

tokio, tokio-threadpool, tokio-executor versions is 0.2.0-alpha.1