Application hanging after KeyboardInterrupt

• uvloop version: 0.14.0
• Python version: 3.7.4
• Platform: Manjaro
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: Yes
• Does uvloop behave differently from vanilla asyncio? How?: With vanilla, the application terminates gracefully upon reception of a keyboard interrupt. If I use uvloop, I get a runtime warning and the application hangs until I run a kill -9 on the process id.

Snippet: issue.py

import asyncio
from asyncio import AbstractEventLoop
import os
from typing import Union, Type

import uvloop  # type: ignore
from aiohttp import web
import signal

import aiologger

logger = aiologger.Logger.with_default_handlers()


async def handle_exception(loop: AbstractEventLoop, context):
    # context["message"] will always be there; but context["exception"] may not
    msg = context.get("exception", context["message"])
    await logger.error(f"Caught exception: {msg}")
    await logger.info("Shutting down...")
    asyncio.create_task(shutdown(loop))


async def shutdown(loop: AbstractEventLoop, signal=None):
    """Cleanup tasks tied to the service's shutdown."""
    if signal:
        await logger.info(f"Received exit signal {signal.name}...")

    tasks = [t for t in asyncio.all_tasks() if t is not asyncio.current_task()]

    [task.cancel() for task in tasks]

    await logger.info(f"Cancelling {len(tasks)} outstanding tasks")
    await asyncio.gather(*tasks, return_exceptions=True)
    loop.stop()


async def start(
    app: web.Application, host: str, port: Union[str, int]
) -> web.AppRunner:
    """Start the server"""
    runner = web.AppRunner(app)
    await runner.setup()
    server = web.TCPSite(runner, host, int(port))
    await server.start()
    return runner


def main() -> None:
    """Entrypoint"""
    host = os.environ.get("HOST", "localhost")
    port = os.environ.get("PORT", 8000)
    app = web.Application()
    loop = asyncio.get_event_loop()
    signals = (signal.SIGHUP, signal.SIGTERM, signal.SIGINT)
    for s in signals:
        loop.add_signal_handler(
            s, lambda s=s: asyncio.create_task(shutdown(loop, signal=s))
        )
    loop.set_exception_handler(handle_exception)
    print(
        f"======== Running on http://{host}:{port} ========\n" "(Press CTRL+C to quit)"
    )
    try:
        runner = loop.run_until_complete(start(app, host, port))
        loop.run_forever()
    finally:
        loop.run_until_complete(runner.cleanup())
        loop.close()


if __name__ == "__main__":
    uvloop.install()
    main()

Run the file:
python issue.py

Then hit Ctrl+c on keyboard, output:

======== Running on http://0.0.0.0:8000 ========
(Press CTRL+C to quit)
^Cissue.py:70: RuntimeWarning: coroutine 'handle_exception' was never awaited
Coroutine created at (most recent call last)
  File "issue.py", line 78, in <module>
    main()
  File "issue.py", line 70, in main
    loop.run_forever()
  loop.run_forever()
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

Which hangs until running kill -9 <pid>

If you comment out uvloop.install() and follow the same steps, the program terminates as expected. Output:

======== Running on http://0.0.0.0:8000 ========
(Press CTRL+C to quit)
^CReceived exit signal SIGINT...
Cancelling 0 outstanding tasks

Führen Sie zunächst issue.py mit uvloop 0.14.0, Python 3.7.4 und aktiviertem PYTHONASYNCIODEBUG aus und vergleichen Sie anschließend dessen Verhalten bei Ctrl+C mit vanilla asyncio. Untersuchen Sie die im Snippet gezeigte Ausnahmebehandlung der Event-Schleife und den Pfad zum Herunterfahren nach einem Signal. Als erledigt gilt die Aufgabe, wenn KeyboardInterrupt eine ordnungsgemäße Bereinigung auslöst, ohne die Warnung zu einer nicht erwarteten Coroutine oder einen hängenden Prozess.