commit a2e0da98669a7a173e25a6abe6e3e2e996be8e67 Author: Damian Johnson atagar@torproject.org Date: Sun Jul 12 17:01:18 2020 -0700

Fix deadlock when stopping from an async context

Reentrant locks can only be acquired multiple from within the same thread. When our _run_async_method() invoked start() or stop() we deadlocked. --- stem/util/__init__.py | 6 ++++-- test/unit/util/synchronous.py | 14 ++++++++++++++ 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/stem/util/__init__.py b/stem/util/__init__.py index c147a5a4..fbd844f8 100644 --- a/stem/util/__init__.py +++ b/stem/util/__init__.py @@ -350,9 +350,11 @@ class Synchronous(object): async def convert_generator(generator: AsyncIterator) -> Iterator: return iter([d async for d in generator])

- return asyncio.run_coroutine_threadsafe(convert_generator(func(self, *args, **kwargs)), self._loop).result() + future = asyncio.run_coroutine_threadsafe(convert_generator(func(self, *args, **kwargs)), self._loop) else: - return asyncio.run_coroutine_threadsafe(func(self, *args, **kwargs), self._loop).result() + future = asyncio.run_coroutine_threadsafe(func(self, *args, **kwargs), self._loop) + + return future.result()

def __iter__(self) -> Iterator: return self._run_async_method('__aiter__') diff --git a/test/unit/util/synchronous.py b/test/unit/util/synchronous.py index d4429f3e..bbf91d18 100644 --- a/test/unit/util/synchronous.py +++ b/test/unit/util/synchronous.py @@ -118,6 +118,20 @@ class TestSynchronous(unittest.TestCase): sync_test() asyncio.run(async_test())

+ def test_stop_from_async(self): + """ + Ensure we can stop our instance from within an async method without + deadlock. + """ + + class AsyncStop(Synchronous): + async def call_stop(self): + self.stop() + + instance = AsyncStop() + instance.call_stop() + self.assertRaises(RuntimeError, instance.call_stop) + def test_resuming(self): """ Resume a previously stopped instance.