import asyncio


async def create_waiter(lock, fut):
    fut.set_result(True)
    async with lock:
        pass

async def main(loop):

    lock = asyncio.Lock()

    await lock.acquire()

    fut = loop.create_future()
    task = asyncio.ensure_future(create_waiter(lock, fut))
    await fut

    lock.release()
    task.cancel()
    #await asyncio.sleep(0)

    print("DEADLOCK HERE")
    print("_locked: ", lock._locked)
    print("_waiters:", lock._waiters)
    async with lock:
        pass


loop = asyncio.get_event_loop()
loop.run_until_complete(main(loop))