gh-128552: fix refcycles in eager task creation (#128553)

2 files changed, 12 insertions, 2 deletions

diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index 9e6f6e3..6e6e5aa 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -477,7 +477,12 @@ class BaseEventLoop(events.AbstractEventLoop):
 
             task.set_name(name)
 
-        return task
+        try:
+            return task
+        finally:
+            # gh-128552: prevent a refcycle of
+            # task.exception().__traceback__->BaseEventLoop.create_task->task
+            del task
 
     def set_task_factory(self, factory):
         """Set a task factory that will be used by loop.create_task().
diff --git a/Lib/asyncio/taskgroups.py b/Lib/asyncio/taskgroups.py
index 9fa772c..8af199d 100644
--- a/Lib/asyncio/taskgroups.py
+++ b/Lib/asyncio/taskgroups.py
@@ -205,7 +205,12 @@ class TaskGroup:
         else:
             self._tasks.add(task)
             task.add_done_callback(self._on_task_done)
-        return task
+        try:
+            return task
+        finally:
+            # gh-128552: prevent a refcycle of
+            # task.exception().__traceback__->TaskGroup.create_task->task
+            del task
 
     # Since Python 3.8 Tasks propagate all exceptions correctly,
     # except for KeyboardInterrupt and SystemExit which are