Ilooping senders starve other tasks

[brson]

Depending on number of threads and steal results this test case may livelock, and probably exhaust memory:

fn periodical(n: int) -> Port<bool> {
    let (port, chan) = stream();
    do spawn {
        println(fmt!("periodical %d - begin", n));
        loop {
            for _ in range(1, n) {
                println(fmt!("periodical %d - sending...", n));
                chan.send(false);
                println(fmt!("periodical %d - sent", n));
            }
            chan.send(true);
        }
    }
    return port;
}

fn integers() -> Port<int> {
    let (port, chan) = stream();
    do spawn {
        println("integers - begin");
        let mut i = 1;
        loop {
            chan.send(i);
            i = i + 1;
        }
    }
    return port;
}

fn main() {
    let ints = integers();
    let threes = periodical(3);
    let fives = periodical(5);
    for _ in range(1, 100) {
        match (ints.recv(), threes.recv(), fives.recv()) {
            (_, true, true) => println("FizzBuzz"),
            (_, true, false) => println("Fizz"),
            (_, false, true) => println("Buzz"),
            (i, false, false) => println(fmt!("%d", i))
        }
    }
}

[alexcrichton]

This appears to no longer be a problem. Even if all the prints are removed (which trigger task scheduling), this test completes.

Flagging as needstest.