GitHub Action Windows x64 CI:
https://github.com/python/cpython/runs/3342514542

First, test_regrtest was killed after 20 minutes, while it was running test_tools_script_run_tests(). Then, re-running test_regrtest in verbose mode failed with a PermissionError.

2021-08-16T17:33:22.5453810Z 0:21:19 load avg: 0.02 [428/428/3] test_regrtest crashed (Exit code 1)
2021-08-16T17:33:22.5454836Z Timeout (0:20:00)!
2021-08-16T17:33:22.5456120Z Thread 0x00000d2c (most recent call first):
2021-08-16T17:33:22.5457237Z   File "D:\a\cpython\cpython\lib\subprocess.py", line 1493 in _readerthread
2021-08-16T17:33:22.5459078Z   File "D:\a\cpython\cpython\lib\threading.py", line 946 in run
2021-08-16T17:33:22.5460342Z   File "D:\a\cpython\cpython\lib\threading.py", line 1009 in _bootstrap_inner
2021-08-16T17:33:22.5461365Z   File "D:\a\cpython\cpython\lib\threading.py", line 966 in _bootstrap
2021-08-16T17:33:22.5461983Z 
2021-08-16T17:33:22.5462583Z Thread 0x000002e8 (most recent call first):
2021-08-16T17:33:22.5464628Z   File "D:\a\cpython\cpython\lib\threading.py", line 1099 in _wait_for_tstate_lock
2021-08-16T17:33:22.5466364Z   File "D:\a\cpython\cpython\lib\threading.py", line 1083 in join
2021-08-16T17:33:22.5468053Z   File "D:\a\cpython\cpython\lib\subprocess.py", line 1522 in _communicate
2021-08-16T17:33:22.5469685Z   File "D:\a\cpython\cpython\lib\subprocess.py", line 1148 in communicate
2021-08-16T17:33:22.5471344Z   File "D:\a\cpython\cpython\lib\subprocess.py", line 503 in run
2021-08-16T17:33:22.5473016Z   File "D:\a\cpython\cpython\lib\test\test_regrtest.py", line 521 in run_command
2021-08-16T17:33:22.5474852Z   File "D:\a\cpython\cpython\lib\test\test_regrtest.py", line 546 in run_python
2021-08-16T17:33:22.5476717Z   File "D:\a\cpython\cpython\lib\test\test_regrtest.py", line 600 in run_tests
2021-08-16T17:33:22.5478416Z   File "D:\a\cpython\cpython\lib\test\test_regrtest.py", line 647 in test_tools_script_run_tests
2021-08-16T17:33:22.5480110Z   File "D:\a\cpython\cpython\lib\unittest\case.py", line 549 in _callTestMethod
2021-08-16T17:33:22.5481748Z   File "D:\a\cpython\cpython\lib\unittest\case.py", line 592 in run
2021-08-16T17:33:22.5483362Z   File "D:\a\cpython\cpython\lib\unittest\case.py", line 652 in __call__
2021-08-16T17:33:22.5484975Z   File "D:\a\cpython\cpython\lib\unittest\suite.py", line 122 in run
2021-08-16T17:33:22.5486506Z   File "D:\a\cpython\cpython\lib\unittest\suite.py", line 84 in __call__
2021-08-16T17:33:22.5488012Z   File "D:\a\cpython\cpython\lib\unittest\suite.py", line 122 in run
2021-08-16T17:33:22.5489316Z   File "D:\a\cpython\cpython\lib\unittest\suite.py", line 84 in __call__
2021-08-16T17:33:22.5490786Z   File "D:\a\cpython\cpython\lib\unittest\suite.py", line 122 in run
2021-08-16T17:33:22.5492556Z   File "D:\a\cpython\cpython\lib\unittest\suite.py", line 84 in __call__
2021-08-16T17:33:22.5494071Z   File "D:\a\cpython\cpython\lib\unittest\runner.py", line 176 in run
2021-08-16T17:33:22.5495666Z   File "D:\a\cpython\cpython\lib\test\support\__init__.py", line 997 in _run_suite
2021-08-16T17:33:22.5496563Z     test_curses test_dbm_gnu test_dbm_ndbm test_devpoll test_epoll
2021-08-16T17:33:22.5497530Z   File "D:\a\cpython\cpython\lib\test\support\__init__.py", line 1122 in run_unittest
2021-08-16T17:33:22.5498484Z     test_fcntl test_fork1 test_gdb test_grp test_ioctl test_kqueue
2021-08-16T17:33:22.5499441Z   File "D:\a\cpython\cpython\lib\test\libregrtest\runtest.py", line 261 in _test_module
2021-08-16T17:33:22.5500545Z     test_multiprocessing_fork test_multiprocessing_forkserver test_nis
2021-08-16T17:33:22.5501639Z   File "D:\a\cpython\cpython\lib\test\libregrtest\runtest.py", line 297 in _runtest_inner2
2021-08-16T17:33:22.5502797Z     test_openpty test_ossaudiodev test_pipes test_poll test_posix
2021-08-16T17:33:22.5503867Z   File "D:\a\cpython\cpython\lib\test\libregrtest\runtest.py", line 335 in _runtest_inner
2021-08-16T17:33:22.5504886Z     test_pty test_pwd test_readline test_resource test_spwd
2021-08-16T17:33:22.5505946Z   File "D:\a\cpython\cpython\lib\test\libregrtest\runtest.py", line 202 in _runtest
2021-08-16T17:33:22.5506925Z     test_syslog test_threadsignals test_wait3 test_wait4
2021-08-16T17:33:22.5507892Z   File "D:\a\cpython\cpython\lib\test\libregrtest\runtest.py", line 245 in runtest
2021-08-16T17:33:22.5508801Z     test_xxtestfuzz test_zipfile64
2021-08-16T17:33:22.5509740Z   File "D:\a\cpython\cpython\lib\test\libregrtest\runtest_mp.py", line 83 in run_tests_worker
2021-08-16T17:33:22.5511140Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 675 in _main
2021-08-16T17:33:22.5512662Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 655 in main
2021-08-16T17:33:22.5513586Z     test_asyncio test_concurrent_futures test_regrtest
2021-08-16T17:33:22.5514516Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 733 in main
2021-08-16T17:33:22.5515982Z   File "D:\a\cpython\cpython\lib\test\regrtest.py", line 43 in _main
2021-08-16T17:33:22.5517908Z   File "D:\a\cpython\cpython\lib\test\regrtest.py", line 47 in <module>
2021-08-16T17:33:22.5520342Z   File "D:\a\cpython\cpython\lib\runpy.py", line 86 in _run_code
2021-08-16T17:33:22.5521322Z   File "D:\a\cpython\cpython\lib\runpy.py", line 196 in _run_module_as_main
(...)
2021-08-16T17:33:25.6698180Z 0:21:22 load avg: 0.01 Re-running test_regrtest in verbose mode
2021-08-16T17:33:25.7418249Z Traceback (most recent call last):
2021-08-16T17:33:25.7419935Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 396, in temp_dir
2021-08-16T17:33:25.7420863Z     yield path
2021-08-16T17:33:25.7421674Z     ^^^^^^^^^^
2021-08-16T17:33:25.7422399Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 449, in temp_cwd
2021-08-16T17:33:25.7433248Z     yield cwd_dir
2021-08-16T17:33:25.7434246Z     ^^^^^^^^^^^^^
2021-08-16T17:33:25.7435032Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 655, in main
2021-08-16T17:33:25.7435868Z     self._main(tests, kwargs)
2021-08-16T17:33:25.7436399Z     ^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7437160Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 728, in _main
2021-08-16T17:33:25.7438083Z     sys.exit(0)
2021-08-16T17:33:25.7438591Z     ^^^^^^^^^^^
2021-08-16T17:33:25.7439133Z SystemExit: 0
2021-08-16T17:33:25.7439483Z 
2021-08-16T17:33:25.7440281Z During handling of the above exception, another exception occurred:
2021-08-16T17:33:25.7440906Z 
2021-08-16T17:33:25.7441466Z Traceback (most recent call last):
2021-08-16T17:33:25.7442312Z   File "D:\a\cpython\cpython\lib\test\support\__init__.py", line 191, in _force_run
2021-08-16T17:33:25.7443113Z     return func(*args)
2021-08-16T17:33:25.7443672Z            ^^^^^^^^^^^
2021-08-16T17:33:25.7446594Z PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'D:\\a\\cpython\\cpython\\build\\test_python_1976�\\test_python_worker_3504�'
2021-08-16T17:33:25.7447646Z 
2021-08-16T17:33:25.7448449Z During handling of the above exception, another exception occurred:
2021-08-16T17:33:25.7449020Z 
2021-08-16T17:33:25.7449617Z Traceback (most recent call last):
2021-08-16T17:33:25.7450443Z   File "D:\a\cpython\cpython\lib\runpy.py", line 196, in _run_module_as_main
2021-08-16T17:33:25.7451253Z     return _run_code(code, main_globals, None,
2021-08-16T17:33:25.7451964Z            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7452625Z   File "D:\a\cpython\cpython\lib\runpy.py", line 86, in _run_code
2021-08-16T17:33:25.7453378Z     exec(code, run_globals)
2021-08-16T17:33:25.7455186Z     ^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7455860Z   File "D:\a\cpython\cpython\lib\test\__main__.py", line 2, in <module>
2021-08-16T17:33:25.7457168Z     main()
2021-08-16T17:33:25.7457604Z     ^^^^^^
2021-08-16T17:33:25.7458336Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 733, in main
2021-08-16T17:33:25.7459194Z     Regrtest().main(tests=tests, **kwargs)
2021-08-16T17:33:25.7459769Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7460528Z   File "D:\a\cpython\cpython\lib\test\libregrtest\main.py", line 649, in main
2021-08-16T17:33:25.7461374Z     with os_helper.temp_cwd(test_cwd, quiet=True):
2021-08-16T17:33:25.7462043Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7462787Z   File "D:\a\cpython\cpython\lib\contextlib.py", line 153, in __exit__
2021-08-16T17:33:25.7463678Z     self.gen.throw(typ, value, traceback)
2021-08-16T17:33:25.7464729Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7465461Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 447, in temp_cwd
2021-08-16T17:33:25.7466377Z     with temp_dir(path=name, quiet=quiet) as temp_path:
2021-08-16T17:33:25.7467243Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7467944Z   File "D:\a\cpython\cpython\lib\contextlib.py", line 153, in __exit__
2021-08-16T17:33:25.7468797Z     self.gen.throw(typ, value, traceback)
2021-08-16T17:33:25.7469408Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7470182Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 401, in temp_dir
2021-08-16T17:33:25.7471114Z     rmtree(path)
2021-08-16T17:33:25.7471591Z     ^^^^^^^^^^^^
2021-08-16T17:33:25.7472342Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 358, in rmtree
2021-08-16T17:33:25.7473077Z     _rmtree(path)
2021-08-16T17:33:25.7473676Z     ^^^^^^^^^^^^^
2021-08-16T17:33:25.7474441Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 301, in _rmtree
2021-08-16T17:33:25.7475690Z     _waitfor(_rmtree_inner, path, waitall=True)
2021-08-16T17:33:25.7476344Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7477086Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 246, in _waitfor
2021-08-16T17:33:25.7477875Z     func(pathname)
2021-08-16T17:33:25.7478398Z     ^^^^^^^^^^^^^^
2021-08-16T17:33:25.7479130Z   File "D:\a\cpython\cpython\lib\test\support\os_helper.py", line 298, in _rmtree_inner
2021-08-16T17:33:25.7480240Z     _force_run(fullname, os.rmdir, fullname)
2021-08-16T17:33:25.7480851Z     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2021-08-16T17:33:25.7481603Z   File "D:\a\cpython\cpython\lib\test\support\__init__.py", line 197, in _force_run
2021-08-16T17:33:25.7482298Z 
2021-08-16T17:33:25.7482896Z     return func(*args)
2021-08-16T17:33:25.7483533Z ----------------------------------------------------------------------
2021-08-16T17:33:25.7484530Z            ^^^^^^^^^^^
2021-08-16T17:33:25.7484753Z 
2021-08-16T17:33:25.7486229Z PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'D:\\a\\cpython\\cpython\\build\\test_python_1976�\\test_python_worker_3504�'
2021-08-16T17:33:25.7487341Z Ran 0 tests in 0.000s

In another commit of the same PR 27774, I don't even see test_regrtest in the list of the "10 slowest tests", so test_regrtest took less than "test_socket: 46.4 sec".

If test_regrtest is killed after 20 minutes, it's likely that it was stuck somewhere.

test_tools_script_run_tests() runs Tools/scripts/run_tests.py with command line arguments.

In the past, I see many issues with PermissionError: something prevents to delete a directory on Windows. I never understood what.

regrtest creates a temporary directory, run a process in this directory, and then removes the directory. Here, something is stuck.