bpo-38356: Fix ThreadedChildWatcher thread leak in test_asyncio (GH-16552)
Motivation for this PR (comment from @vstinner in bpo issue):
```
Warning seen o AMD64 Ubuntu Shared 3.x buildbot:
https://buildbot.python.org/all/#/builders/141/builds/2593
test_devnull_output (test.test_a=syncio.test_subprocess.SubprocessThreadedWatcherTests) ...
Warning -- threading_cleanup() failed to cleanup 1 threads (count: 1, dangling: 2)
```
The following implementation details for the new method are TBD:
1) Public vs private
2) Inclusion in `close()`
3) Name
4) Coroutine vs subroutine method
5) *timeout* parameter
If it's a private method, 3, 4, and 5 are significantly less important.
I started with the most minimal implementation that fixes the dangling threads without modifying the regression tests, which I think is particularly important. I typically try to avoid directly modifying existing tests as much as possible unless it's necessary to do so. However, I am open to changing any part of this.
https://bugs.python.org/issue38356
diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
index 28fb491..19d7135 100644
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -1344,7 +1344,14 @@
return True
def close(self):
- pass
+ self._join_threads()
+
+ def _join_threads(self):
+ """Internal: Join all non-daemon threads"""
+ threads = [thread for thread in list(self._threads.values())
+ if thread.is_alive() and not thread.daemon]
+ for thread in threads:
+ thread.join()
def __enter__(self):
return self