`test_free_threading.test_monitoring` flaky (occasional reference leak)

Bug report

When running ./python -E -m test --timeout=2700 -R3:3 -u-cpu -j40 test_free_threading.test_monitoring -F, I get a failure every ~50-100 test runs:

0:00:36 load avg: 122.12 [ 55/1] test_free_threading.test_monitoring failed (reference leak)
beginning 6 repetitions. Showing number of leaks (. for 0 or less, X for 10 or more)
123:456
XX. 243
test_free_threading.test_monitoring leaked [2, 4, 3] memory blocks, sum=9

I think the issue is that we rely on Thread.is_alive() instead of joining the threads. I think there are still some objects that may not be freed until the thread is joined (like the handle):

https://github.com/python/cpython/blob/cb59eaefeda5ff44ac0c742bff2b8afc023be313/Lib/test/test_free_threading/test_monitoring.py#L65-L77

Linked PRs

• gh-136896
• gh-141832

從 Lib/test/test_free_threading/test_monitoring.py 第 65-77 行附近開始，使用報告中的命令重現洩漏。檢查其中的執行緒清理，然後重新執行重複測試，以確認不再發生參考洩漏；連結的 PR gh-136896 和 gh-141832 表明這項工作已經移到其他地方。