bpo-36607: Eliminate RuntimeError raised by asyncio.all_tasks() (GH-13971)
If internal tasks weak set is changed by another thread during iteration.
https://bugs.python.org/issue36607
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 95e8560..cd4832c 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -42,9 +42,22 @@
"""Return a set of all tasks for the loop."""
if loop is None:
loop = events.get_running_loop()
- # NB: set(_all_tasks) is required to protect
- # from https://bugs.python.org/issue34970 bug
- return {t for t in list(_all_tasks)
+ # Looping over a WeakSet (_all_tasks) isn't safe as it can be updated from another
+ # thread while we do so. Therefore we cast it to list prior to filtering. The list
+ # cast itself requires iteration, so we repeat it several times ignoring
+ # RuntimeErrors (which are not very likely to occur). See issues 34970 and 36607 for
+ # details.
+ i = 0
+ while True:
+ try:
+ tasks = list(_all_tasks)
+ except RuntimeError:
+ i += 1
+ if i >= 1000:
+ raise
+ else:
+ break
+ return {t for t in tasks
if futures._get_loop(t) is loop and not t.done()}
@@ -54,9 +67,22 @@
# method.
if loop is None:
loop = events.get_event_loop()
- # NB: set(_all_tasks) is required to protect
- # from https://bugs.python.org/issue34970 bug
- return {t for t in list(_all_tasks) if futures._get_loop(t) is loop}
+ # Looping over a WeakSet (_all_tasks) isn't safe as it can be updated from another
+ # thread while we do so. Therefore we cast it to list prior to filtering. The list
+ # cast itself requires iteration, so we repeat it several times ignoring
+ # RuntimeErrors (which are not very likely to occur). See issues 34970 and 36607 for
+ # details.
+ i = 0
+ while True:
+ try:
+ tasks = list(_all_tasks)
+ except RuntimeError:
+ i += 1
+ if i >= 1000:
+ raise
+ else:
+ break
+ return {t for t in tasks if futures._get_loop(t) is loop}
def _set_task_name(task, name):