bpo-31249: Fix ref cycle in ThreadPoolExecutor (#3178)
* bpo-31249: Fix ref cycle in ThreadPoolExecutor
concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now
breaks a reference cycle between an exception object and the WorkItem
object. ThreadPoolExecutor.shutdown() now also clears its threads
set.
* shutdown() now only clears threads if wait is true.
* Revert changes on shutdown()
diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index 1f0a1d4..0b5d537 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -54,8 +54,10 @@
try:
result = self.fn(*self.args, **self.kwargs)
- except BaseException as e:
- self.future.set_exception(e)
+ except BaseException as exc:
+ self.future.set_exception(exc)
+ # Break a reference cycle with the exception 'exc'
+ self = None
else:
self.future.set_result(result)