1 files changed, 69 insertions, 0 deletions
diff --git a/third_party/rust/futures/tests/lock_mutex.rs b/third_party/rust/futures/tests/lock_mutex.rs
new file mode 100644
index 0000000000..c15e76bd84
--- /dev/null
+++ b/third_party/rust/futures/tests/lock_mutex.rs
@@ -0,0 +1,69 @@
+use futures::channel::mpsc;
+use futures::executor::{block_on, ThreadPool};
+use futures::future::{ready, FutureExt};
+use futures::lock::Mutex;
+use futures::stream::StreamExt;
+use futures::task::{Context, SpawnExt};
+use futures_test::future::FutureTestExt;
+use futures_test::task::{new_count_waker, panic_context};
+use std::sync::Arc;
+
+#[test]
+fn mutex_acquire_uncontested() {
+    let mutex = Mutex::new(());
+    for _ in 0..10 {
+        assert!(mutex.lock().poll_unpin(&mut panic_context()).is_ready());
+    }
+}
+
+#[test]
+fn mutex_wakes_waiters() {
+    let mutex = Mutex::new(());
+    let (waker, counter) = new_count_waker();
+    let lock = mutex.lock().poll_unpin(&mut panic_context());
+    assert!(lock.is_ready());
+
+    let mut cx = Context::from_waker(&waker);
+    let mut waiter = mutex.lock();
+    assert!(waiter.poll_unpin(&mut cx).is_pending());
+    assert_eq!(counter, 0);
+
+    drop(lock);
+
+    assert_eq!(counter, 1);
+    assert!(waiter.poll_unpin(&mut panic_context()).is_ready());
+}
+
+#[test]
+fn mutex_contested() {
+    {
+        let (tx, mut rx) = mpsc::unbounded();
+        let pool = ThreadPool::builder().pool_size(16).create().unwrap();
+
+        let tx = Arc::new(tx);
+        let mutex = Arc::new(Mutex::new(0));
+
+        let num_tasks = 1000;
+        for _ in 0..num_tasks {
+            let tx = tx.clone();
+            let mutex = mutex.clone();
+            pool.spawn(async move {
+                let mut lock = mutex.lock().await;
+                ready(()).pending_once().await;
+                *lock += 1;
+                tx.unbounded_send(()).unwrap();
+                drop(lock);
+            })
+            .unwrap();
+        }
+
+        block_on(async {
+            for _ in 0..num_tasks {
+                rx.next().await.unwrap();
+            }
+            let lock = mutex.lock().await;
+            assert_eq!(num_tasks, *lock);
+        });
+    }
+    std::thread::sleep(std::time::Duration::from_millis(500)); // wait for background threads closed: https://github.com/rust-lang/miri/issues/1371
+}