Added test to reproduce race condition

Author: Andrew J Westlake

Cargo.toml

@@ -102,6 +102,13 @@ path = "pytests/test_tokio_multi_thread_uvloop.rs"
 harness = false
 required-features = ["tokio-runtime", "testing"]
 
+
+[[test]]
+name = "test_race_condition_regression"
+path = "pytests/test_race_condition_regression.rs"
+harness = false
+required-features = ["async-std-runtime", "testing"]
+
 [dependencies]
 async-channel = { version = "1.6", optional = true }
 clap = { version = "3.1.5", optional = true }

pytests/test_race_condition_regression.rs

@@ -0,0 +1,66 @@
+use pyo3::{prelude::*, wrap_pyfunction};
+
+#[pyfunction]
+fn sleep<'p>(py: Python<'p>, secs: &'p PyAny) -> PyResult<&'p PyAny> {
+    let secs = secs.extract()?;
+
+    pyo3_asyncio::async_std::future_into_py(py, async move {
+        async_std::task::sleep(std::time::Duration::from_secs_f64(secs)).await;
+        Ok(())
+    })
+}
+
+const RACE_CONDITION_REGRESSION_TEST: &str = r#"
+import asyncio
+import random
+
+async def trigger_race_condition(rust_sleeper, delay):
+    coro = asyncio.wrap_future(rust_sleeper(0.1))
+    await asyncio.sleep(delay)
+    coro.cancel()
+
+def main(rust_sleeper):
+    race_condition_triggered = False
+
+    for i in range(1000):
+        delay = random.uniform(0.099, 0.101)
+        loop = asyncio.new_event_loop()
+        loop.set_debug(True)
+
+        def custom_exception_handler(loop, context):
+            nonlocal race_condition_triggered
+            race_condition_triggered = True
+
+        try:
+            loop.set_exception_handler(custom_exception_handler)
+            loop.run_until_complete(trigger_race_condition(rust_sleeper, delay))
+
+            if race_condition_triggered:
+                raise Exception("Race condition triggered")
+
+        finally:
+            loop.run_until_complete(loop.shutdown_asyncgens())
+            if hasattr(loop, 'shutdown_default_executor'):
+                loop.run_until_complete(loop.shutdown_default_executor())
+            loop.close()
+"#;
+
+fn main() -> pyo3::PyResult<()> {
+    pyo3::prepare_freethreaded_python();
+
+    Python::with_gil(|py| -> PyResult<()> {
+        let sleeper_mod = PyModule::new(py, "rust_sleeper")?;
+
+        sleeper_mod.add_wrapped(wrap_pyfunction!(sleep))?;
+
+        let test_mod = PyModule::from_code(
+            py,
+            RACE_CONDITION_REGRESSION_TEST,
+            "race_condition_regression_test.py",
+            "race_condition_regression_test",
+        )?;
+
+        test_mod.call_method1("main", (sleeper_mod.getattr("sleep")?,))?;
+        Ok(())
+    })
+}