153 lines
5.6 KiB
Rust
153 lines
5.6 KiB
Rust
extern crate futures;
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use std::sync::{Arc, Weak};
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use std::thread;
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use std::time::{Duration, Instant};
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use futures::prelude::*;
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use futures::sync::mpsc::*;
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use futures::task;
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#[test]
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fn smoke() {
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let (mut sender, receiver) = channel(1);
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let t = thread::spawn(move ||{
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while let Ok(s) = sender.send(42).wait() {
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sender = s;
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}
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});
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receiver.take(3).for_each(|_| Ok(())).wait().unwrap();
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t.join().unwrap()
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}
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// Stress test that `try_send()`s occurring concurrently with receiver
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// close/drops don't appear as successful sends.
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#[test]
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fn stress_try_send_as_receiver_closes() {
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const AMT: usize = 10000;
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// To provide variable timing characteristics (in the hopes of
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// reproducing the collision that leads to a race), we busy-re-poll
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// the test MPSC receiver a variable number of times before actually
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// stopping. We vary this countdown between 1 and the following
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// value.
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const MAX_COUNTDOWN: usize = 20;
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// When we detect that a successfully sent item is still in the
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// queue after a disconnect, we spin for up to 100ms to confirm that
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// it is a persistent condition and not a concurrency illusion.
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const SPIN_TIMEOUT_S: u64 = 10;
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const SPIN_SLEEP_MS: u64 = 10;
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struct TestRx {
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rx: Receiver<Arc<()>>,
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// The number of times to query `rx` before dropping it.
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poll_count: usize
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}
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struct TestTask {
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command_rx: Receiver<TestRx>,
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test_rx: Option<Receiver<Arc<()>>>,
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countdown: usize,
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}
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impl TestTask {
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/// Create a new TestTask
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fn new() -> (TestTask, Sender<TestRx>) {
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let (command_tx, command_rx) = channel::<TestRx>(0);
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(
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TestTask {
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command_rx: command_rx,
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test_rx: None,
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countdown: 0, // 0 means no countdown is in progress.
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},
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command_tx,
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)
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}
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}
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impl Future for TestTask {
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type Item = ();
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type Error = ();
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fn poll(&mut self) -> Poll<(), ()> {
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// Poll the test channel, if one is present.
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if let Some(ref mut rx) = self.test_rx {
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if let Ok(Async::Ready(v)) = rx.poll() {
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let _ = v.expect("test finished unexpectedly!");
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}
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self.countdown -= 1;
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// Busy-poll until the countdown is finished.
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task::current().notify();
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}
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// Accept any newly submitted MPSC channels for testing.
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match self.command_rx.poll()? {
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Async::Ready(Some(TestRx { rx, poll_count })) => {
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self.test_rx = Some(rx);
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self.countdown = poll_count;
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task::current().notify();
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},
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Async::Ready(None) => return Ok(Async::Ready(())),
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_ => {},
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}
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if self.countdown == 0 {
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// Countdown complete -- drop the Receiver.
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self.test_rx = None;
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}
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Ok(Async::NotReady)
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}
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}
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let (f, mut cmd_tx) = TestTask::new();
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let bg = thread::spawn(move || f.wait());
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for i in 0..AMT {
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let (mut test_tx, rx) = channel(0);
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let poll_count = i % MAX_COUNTDOWN;
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cmd_tx.try_send(TestRx { rx: rx, poll_count: poll_count }).unwrap();
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let mut prev_weak: Option<Weak<()>> = None;
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let mut attempted_sends = 0;
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let mut successful_sends = 0;
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loop {
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// Create a test item.
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let item = Arc::new(());
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let weak = Arc::downgrade(&item);
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match test_tx.try_send(item) {
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Ok(_) => {
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prev_weak = Some(weak);
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successful_sends += 1;
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}
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Err(ref e) if e.is_full() => {}
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Err(ref e) if e.is_disconnected() => {
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// Test for evidence of the race condition.
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if let Some(prev_weak) = prev_weak {
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if prev_weak.upgrade().is_some() {
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// The previously sent item is still allocated.
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// However, there appears to be some aspect of the
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// concurrency that can legitimately cause the Arc
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// to be momentarily valid. Spin for up to 100ms
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// waiting for the previously sent item to be
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// dropped.
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let t0 = Instant::now();
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let mut spins = 0;
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loop {
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if prev_weak.upgrade().is_none() {
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break;
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}
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assert!(t0.elapsed() < Duration::from_secs(SPIN_TIMEOUT_S),
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"item not dropped on iteration {} after \
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{} sends ({} successful). spin=({})",
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i, attempted_sends, successful_sends, spins
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);
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spins += 1;
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thread::sleep(Duration::from_millis(SPIN_SLEEP_MS));
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}
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}
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}
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break;
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}
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Err(ref e) => panic!("unexpected error: {}", e),
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}
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attempted_sends += 1;
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}
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}
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drop(cmd_tx);
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bg.join()
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.expect("background thread join")
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.expect("background thread result");
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}
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