Thread sanitizer (free-threading) tests fail: test_signal raises RecursionError

Bug report

 0:02:53 load avg: 5.00 [ 9/22/1] test_signal failed (1 error) (1 min 1 sec) -- running (3): test_logging (2 min 13 sec), test_io (2 min 17 sec), test_queue (1 min 52 sec)
test test_signal failed -- Traceback (most recent call last):
  File "/home/runner/work/cpython/cpython/Lib/test/test_signal.py", line 1384, in test_stress_modifying_handlers
    cycle_handlers()
    ~~~~~~~~~~~~~~^^
  File "/home/runner/work/cpython/cpython/Lib/test/test_signal.py", line 1374, in cycle_handlers
    signal.signal(signum, handler)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Lib/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
                             ~~~~~~~~~~~~^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Lib/signal.py", line 41, in _enum_to_int
    return int(value)
  File "/home/runner/work/cpython/cpython/Lib/test/test_signal.py", line 1359, in custom_handler
    def custom_handler(signum, frame):
    
  File "/home/runner/work/cpython/cpython/Lib/test/test_signal.py", line 1359, in custom_handler
    def custom_handler(signum, frame):
    
  File "/home/runner/work/cpython/cpython/Lib/test/test_signal.py", line 1359, in custom_handler
    def custom_handler(signum, frame):
    
  [Previous line repeated 237 more times]
RecursionError: maximum recursion depth exceeded

Link: https://github.com/python/cpython/actions/runs/9686054998/job/26727620578

Linked PRs

• gh-121100

從 Lib/test/test_signal.py 開始，特別檢查 test_stress_modifying_handlers、cycle_handlers 和 custom_handler，然後檢查 Lib/signal.py 中 _enum_to_int 附近的程式碼。查看關聯的 gh-121100 工作以了解目前的上下文。當 test_signal 測試在 Thread Sanitizer 的 Free-Threading 執行中不再引發 RecursionError 時，即表示完成。