test_threading fails and crashes when rerun

[serhiy-storchaka]

Crash report

First, BarrierTests.test_default_timeout in test_threading fails, producing also several unraisable exception messages. They are produced even during running few following tests.

https://github.com/python/cpython/actions/runs/6094370280/job/16535778004#step:5:103

test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout ... Warning -- Unraisable exception
Exception ignored in thread started by: <function Bunch.__init__.<locals>.task at 0x053F5270>
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 48, in task
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "D:\a\cpython\cpython\Lib\threading.py", line 749, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError: 
ERROR
test_repr (test.test_threading.BarrierTests.test_repr) ... Warning -- Unraisable exception
Exception ignored in thread started by: <function Bunch.__init__.<locals>.task at 0x053F5270>
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 48, in task
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "D:\a\cpython\cpython\Lib\threading.py", line 749, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError: 
Warning -- Unraisable exception
Exception ignored in thread started by: <function Bunch.__init__.<locals>.task at 0x053F5270>
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 48, in task
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "D:\a\cpython\cpython\Lib\threading.py", line 749, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError: 
Warning -- Unraisable exception
Exception ignored in thread started by: <function Bunch.__init__.<locals>.task at 0x053F5270>
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 48, in task
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 700, in wait
 self._enter() # Block while the barrier drains.
 ^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 724, in _enter
 raise BrokenBarrierError
threading.BrokenBarrierError: 
ok

After rerunning test_threading it crashes.

https://github.com/python/cpython/actions/runs/6094370280/job/16535778004#step:5:1067

0:17:28 Re-running 2 failed tests in verbose mode in subprocesses
0:17:28 Run tests in parallel using 4 child processes (timeout: 20 min, worker timeout: 25 min)
0:17:30 [1/2/1] test_threading process crashed (Exit code 3)
Re-running test_threading in verbose mode (matching: test_default_timeout)
test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout ... Warning -- Unraisable exception
Exception ignored in thread started by: <function Bunch.__init__.<locals>.task at 0x052196F0>
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 48, in task
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "D:\a\cpython\cpython\Lib\threading.py", line 749, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError: 
ERROR

======================================================================
ERROR: test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout
----------------------------------------------------------------------
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1025, in test_default_timeout
 self.run_threads(f)
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 854, in run_threads
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "D:\a\cpython\cpython\Lib\threading.py", line 747, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError

----------------------------------------------------------------------
Ran 1 test in 0.376s

FAILED (errors=1)
test test_threading failed

{"test_name": "test_threading", "state": "FAILED", "duration": 0.6816820999999891, "xml_data": null, "stats":{"tests_run": 1, "failures": 0, "skipped": 0}, "errors": [["test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)", "Traceback (most recent call last):\n File \"D:\\a\\cpython\\cpython\\Lib\\test\\lock_tests.py\", line 1025, in test_default_timeout\n self.run_threads(f)\n File \"D:\\a\\cpython\\cpython\\Lib\\test\\lock_tests.py\", line 854, in run_threads\n f()\n File \"D:\\a\\cpython\\cpython\\Lib\\test\\lock_tests.py\", line 1020, in f\n i = barrier.wait()\n ^^^^^^^^^^^^^^\n File \"D:\\a\\cpython\\cpython\\Lib\\threading.py\", line 709, in wait\n self._wait(timeout)\n File \"D:\\a\\cpython\\cpython\\Lib\\threading.py\", line 747, in _wait\n raise BrokenBarrierError\nthreading.BrokenBarrierError\n"]], "failures": [], "__test_result__": "TestResult"}
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�Fatal Python error: Aborted

Thread 0x0000186c (most recent call first):
 <no Python frame>
1 test failed again:
 test_threading

Note also UTF-16 in logs, but this is other issue.

It only happened in Windows (x86) run, the run on Windows (x64) passed successfully, as well as on other platforms. It may be 32-bit Windows specific or random.

Linked PRs

• gh-108987: Fix _thread.start_new_thread() race condition #109135
• [3.11] gh-108987: Fix _thread.start_new_thread() race condition (#109135) #109272
• [3.12] gh-108987: Fix _thread.start_new_thread() race condition (#109135) #110342

[terryjreedy]

Running just python -m test -v test_threading (main) on my Win10 gives different newish and reproducible failures.

======================================================================
FAIL: test_daemon_threads_not_allowed (test.test_threading.SubinterpThreadingTests.test_daemon_threads_not_allowed) [via Thread()]
----------------------------------------------------------------------
Traceback (most recent call last):
 File "f:\dev\3x\Lib\test\test_threading.py", line 1367, in test_daemon_threads_not_allowed
 err = self._check_allowed(
 ^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\test_threading.py", line 1352, in _check_allowed
 _, _, err = assert_python_ok("-c", script)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 166, in assert_python_ok
 return _assert_python(True, *args, **env_vars)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 151, in _assert_python
 res.fail(cmd_line)
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 76, in fail
 raise AssertionError("Process return code is %d\n"
AssertionError: Process return code is 1
command line: ['f:\\dev\\3x\\PCbuild\\amd64\\python_d.exe', '-X', 'faulthandler', '-c', '\nimport test.support\ntest.support.run_in_subinterp_with_config(\n "\\nimport test.support\\nimport threading\\ndef func():\\n print(\'this should not have run!\')\\nt = threading.Thread(target=func, daemon=True)\\n\\nt.start()\\n",\n use_main_obmalloc=True,\n allow_fork=True,\n allow_exec=True,\n allow_threads=True,\n allow_daemon_threads=False,\n check_multi_interp_extensions=False,\n own_gil=False,\n)\n']

stdout:
---

---

stderr:
---
Traceback (most recent call last):
 File "<string>", line 3, in <module>
 File "f:\dev\3x\Lib\test\support\__init__.py", line 1859, in run_in_subinterp_with_config
 return _testinternalcapi.run_in_subinterp_with_config(code, **config)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module '_testinternalcapi' has no attribute 'run_in_subinterp_with_config'
---

======================================================================
FAIL: test_daemon_threads_not_allowed (test.test_threading.SubinterpThreadingTests.test_daemon_threads_not_allowed) [via Thread.daemon setter]
----------------------------------------------------------------------
Traceback (most recent call last):
 File "f:\dev\3x\Lib\test\test_threading.py", line 1375, in test_daemon_threads_not_allowed
 err = self._check_allowed(
 ^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\test_threading.py", line 1352, in _check_allowed
 _, _, err = assert_python_ok("-c", script)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 166, in assert_python_ok
 return _assert_python(True, *args, **env_vars)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 151, in _assert_python
 res.fail(cmd_line)
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 76, in fail
 raise AssertionError("Process return code is %d\n"
AssertionError: Process return code is 1
command line: ['f:\\dev\\3x\\PCbuild\\amd64\\python_d.exe', '-X', 'faulthandler', '-c', '\nimport test.support\ntest.support.run_in_subinterp_with_config(\n "\\nimport test.support\\nimport threading\\ndef func():\\n print(\'this should not have run!\')\\nt = threading.Thread(target=func, daemon=False)\\nt.daemon = True\\nt.start()\\n",\n use_main_obmalloc=True,\n allow_fork=True,\n allow_exec=True,\n allow_threads=True,\n allow_daemon_threads=False,\n check_multi_interp_extensions=False,\n own_gil=False,\n)\n']

stdout:
---

---

stderr:
---
Traceback (most recent call last):
 File "<string>", line 3, in <module>
 File "f:\dev\3x\Lib\test\support\__init__.py", line 1859, in run_in_subinterp_with_config
 return _testinternalcapi.run_in_subinterp_with_config(code, **config)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module '_testinternalcapi' has no attribute 'run_in_subinterp_with_config'
---

======================================================================
FAIL: test_threads_not_allowed (test.test_threading.SubinterpThreadingTests.test_threads_not_allowed)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "f:\dev\3x\Lib\test\test_threading.py", line 1357, in test_threads_not_allowed
 err = self._check_allowed(
 ^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\test_threading.py", line 1352, in _check_allowed
 _, _, err = assert_python_ok("-c", script)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 166, in assert_python_ok
 return _assert_python(True, *args, **env_vars)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 151, in _assert_python
 res.fail(cmd_line)
 File "f:\dev\3x\Lib\test\support\script_helper.py", line 76, in fail
 raise AssertionError("Process return code is %d\n"
AssertionError: Process return code is 1
command line: ['f:\\dev\\3x\\PCbuild\\amd64\\python_d.exe', '-X', 'faulthandler', '-c', '\nimport test.support\ntest.support.run_in_subinterp_with_config(\n "\\nimport test.support\\nimport threading\\ndef func():\\n print(\'this should not have run!\')\\nt = threading.Thread(target=func, daemon=False)\\n\\nt.start()\\n",\n use_main_obmalloc=True,\n allow_fork=True,\n allow_exec=True,\n allow_threads=False,\n allow_daemon_threads=False,\n check_multi_interp_extensions=False,\n own_gil=False,\n)\n']

stdout:
---

---

stderr:
---
Traceback (most recent call last):
 File "<string>", line 3, in <module>
 File "f:\dev\3x\Lib\test\support\__init__.py", line 1859, in run_in_subinterp_with_config
 return _testinternalcapi.run_in_subinterp_with_config(code, **config)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module '_testinternalcapi' has no attribute 'run_in_subinterp_with_config'
---

[vstinner]

I'm able to reproduce the issue on Windows 11 with Python built in 32-bit mode. See Assertion failed: tstate_is_alive(tstate) in my logs.

It seems like the assertion error requires precise timing to be triggered.

Output (reformatted for readability):

vstinner@WIN C:\victor\python\main>python -m test -v test_threading --forever -m test_default_timeout -j20 --rerun 
Running Debug|Win32 interpreter...
== CPython 3.13.0a0 (heads/main:a0773b89df, Sep 7 2023, 07:59:33) [MSC v.1936 32 bit (Intel)]
== Windows-11-10.0.22621-SP0 little-endian
== Python build: debug
== cwd: C:\victor\python\main\build\test_python_1116æ
== CPU count: 2
== encodings: locale=cp1252, FS=utf-8


0:00:00 Run tests in parallel using 20 child processes
0:00:05 [ 1/1] test_threading process crashed (Exit code 3)
test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout ... ERROR

======================================================================
ERROR: test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout
----------------------------------------------------------------------
Traceback (most recent call last):
 File "C:\victor\python\main\Lib\test\lock_tests.py", line 1025, in test_default_timeout
 self.run_threads(f)
 File "C:\victor\python\main\Lib\test\lock_tests.py", line 854, in run_threads
 f()
 File "C:\victor\python\main\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "C:\victor\python\main\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "C:\victor\python\main\Lib\threading.py", line 747, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError

----------------------------------------------------------------------
Ran 1 test in 0.466s

FAILED (errors=1)
test test_threading failed

{"test_name": "test_threading", "state": "FAILED", "duration": 1.5271271999999954, "xml_data": null, "stats":{"tests_run": 1, "failures": 0, "skipped": 0}, "errors": [["test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)", "Traceback (most recent call last):\n File \"C:\\victor\\python\\main\\Lib\\test\\lock_tests.py\", line 1025, in test_default_timeout\n self.run_threads(f)\n File \"C:\\victor\\python\\main\\Lib\\test\\lock_tests.py\", line 854, in run_threads\n f()\n File \"C:\\victor\\python\\main\\Lib\\test\\lock_tests.py\", line 1020, in f\n i = barrier.wait()\n ^^^^^^^^^^^^^^\n File \"C:\\victor\\python\\main\\Lib\\threading.py\", line 709, in wait\n self._wait(timeout)\n File \"C:\\victor\\python\\main\\Lib\\threading.py\", line 747, in _wait\n raise BrokenBarrierError\nthreading.BrokenBarrierError\n"]], "failures": [], "__test_result__": "TestResult"}

Assertion failed: tstate_is_alive(tstate) && !tstate->_status.bound, file C:\victor\python\main\Python\pystate.c, line 245 
Fatal Python error: Aborted

Thread 0x00000854 (most recent call first):
 <no Python frame>
(...)

[vstinner]

The test_default_timeout() failured with the Warning -- Unraisable exception log can be reproduced on Linux by stressing the machine with many processes, way more than the number of CPUs.

Example of my laptop with 12 thread (6 CPU cores):

$ ./python -m test -v test_threading --forever -m test_default_timeout -j200 --rerun 
(...)
0:00:25 load avg: 63.13 [101] test_threading passed
test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout ... ok

----------------------------------------------------------------------
Ran 1 test in 2.763s

OK
0:00:25 load avg: 63.13 [102/1] test_threading failed (1 error)
test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout ... ERROR

======================================================================
ERROR: test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/vstinner/python/main/Lib/test/lock_tests.py", line 1025, in test_default_timeout
 self.run_threads(f)
 File "/home/vstinner/python/main/Lib/test/lock_tests.py", line 854, in run_threads
 f()
 File "/home/vstinner/python/main/Lib/test/lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "/home/vstinner/python/main/Lib/threading.py", line 709, in wait
 self._wait(timeout)
 File "/home/vstinner/python/main/Lib/threading.py", line 747, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError

----------------------------------------------------------------------
Ran 1 test in 0.314s

FAILED (errors=1)
Warning -- Unraisable exception
Exception ignored in thread started by: <function Bunch.__init__.<locals>.task at 0x7fb63cbb5f10>
Traceback (most recent call last):
 File "/home/vstinner/python/main/Lib/test/lock_tests.py", line 48, in task
 f()
 File "/home/vstinner/python/main/Lib/test/lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "/home/vstinner/python/main/Lib/threading.py", line 709, in wait
 self._wait(timeout)
 File "/home/vstinner/python/main/Lib/threading.py", line 749, in _wait
(...)

[vstinner]

Oh, the GitHub Action Windows x64 job is also affected by this bug.

Log reformatted to make them more readable (I removed NUL bytes, add empty lines):

0:17:13 Re-running 2 failed tests in verbose mode in subprocesses
0:17:13 Run tests in parallel using 4 child processes (timeout: 20 min, worker timeout: 25 min)
0:17:14 [1/2/1] test_threading process crashed (Exit code 3)
Re-running test_threading in verbose mode (matching: test_default_timeout)
Kill <WorkerThread #2 running test=test.test_concurrent_futures.test_as_completed pid=1364 time=1.1 sec>
test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout ... ERROR

======================================================================
ERROR: test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)
Test the barrier's default timeout
----------------------------------------------------------------------
Traceback (most recent call last):
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1025, in test_default_timeout
 self.run_threads(f)
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 854, in run_threads
 f()
 File "D:\a\cpython\cpython\Lib\test\lock_tests.py", line 1020, in f
 i = barrier.wait()
 ^^^^^^^^^^^^^^
 File "D:\a\cpython\cpython\Lib\threading.py", line 709, in wait
 self._wait(timeout)
 File "D:\a\cpython\cpython\Lib\threading.py", line 747, in _wait
 raise BrokenBarrierError
threading.BrokenBarrierError

----------------------------------------------------------------------
Ran 1 test in 0.366s

FAILED (errors=1)
test test_threading failed

{"test_name": "test_threading", "state": "FAILED", "duration": 0.6854470000000674, "xml_data": null, "stats":{"tests_run": 1, "failures": 0, "skipped": 0}, "errors": [["test_default_timeout (test.test_threading.BarrierTests.test_default_timeout)", "Traceback (most recent call last):\n File \"D:\\a\\cpython\\cpython\\Lib\\test\\lock_tests.py\", line 1025, in test_default_timeout\n self.run_threads(f)\n File \"D:\\a\\cpython\\cpython\\Lib\\test\\lock_tests.py\", line 854, in run_threads\n f()\n File \"D:\\a\\cpython\\cpython\\Lib\\test\\lock_tests.py\", line 1020, in f\n i = barrier.wait()\n ^^^^^^^^^^^^^^\n File \"D:\\a\\cpython\\cpython\\Lib\\threading.py\", line 709, in wait\n self._wait(timeout)\n File \"D:\\a\\cpython\\cpython\\Lib\\threading.py\", line 747, in _wait\n raise BrokenBarrierError\nthreading.BrokenBarrierError\n"]], "failures": [], "__test_result__": "TestResult"}

Assertion failed: !_PyMem_IsPtrFreed(tstate->interp), file D:\a\cpython\cpython\Python\pystate.c, line 2905
Fatal Python error: Aborted

Thread 0x00001500 (most recent call first):
 <no Python frame>

Extension modules: _wmi (total: 1)
Assertion failed: !_PyMem_IsPtrFreed(tstate->interp), file D:\a\cpython\cpython\Python\pystate.c, line 2905

1 test failed again:
 test_threading

I had to download logs manually and remove null bytes, the two assertion errors are written in UTF-16 in a 8-bit console, and so the log is full of NUL bytes. I removed these NUL bytes.

---

By the way, the regrtest final report is a little bit surprising.

First, 2 tests failed:

• test.test_concurrent_futures.test_as_completed
• test_threading

Then, these 2 tests were run again. But test_threading crashed, regrtest failed to get the JSON from the output which is polluted by assertion errors. In that case, regrtest kills other worker processes, and stops immediately.

The surprised part is that the final report lists test.test_concurrent_futures.test_as_completed in omitted tests:

== Tests result: FAILURE then FAILURE ==

1 test omitted:
 test.test_concurrent_futures.test_as_completed

422 tests OK.

10 slowest tests:
- test_importlib: 3 min 1 sec
- test_regrtest: 2 min 57 sec
- test.test_multiprocessing_spawn.test_processes: 2 min 47 sec
- test.test_multiprocessing_spawn.test_misc: 1 min 49 sec
- test.test_multiprocessing_spawn.test_manager: 1 min 37 sec
- test_socket: 1 min 30 sec
- test_mmap: 1 min 30 sec
- test_tarfile: 1 min 24 sec
- test_zipfile: 1 min 23 sec
- test_compileall: 1 min 19 sec

1 test failed:
 test_threading

37 tests skipped:
 test.test_asyncio.test_unix_events
 test.test_multiprocessing_fork.test_manager
 test.test_multiprocessing_fork.test_misc
 test.test_multiprocessing_fork.test_processes
 test.test_multiprocessing_fork.test_threads
 test.test_multiprocessing_forkserver.test_manager
 test.test_multiprocessing_forkserver.test_misc
 test.test_multiprocessing_forkserver.test_processes
 test.test_multiprocessing_forkserver.test_threads test_curses
 test_dbm_gnu test_dbm_ndbm test_devpoll test_epoll test_fcntl
 test_fork1 test_gdb test_grp test_ioctl test_kqueue test_msvcrt
 test_openpty test_perf_profiler test_perfmaps test_poll test_posix
 test_pty test_pwd test_readline test_resource test_syslog
 test_threadsignals test_wait3 test_wait4 test_xxlimited
 test_xxtestfuzz test_zoneinfo

2 tests skipped (resource denied):
 test_peg_generator test_zipfile64

1 re-run test:
 test_threading

Total duration: 17 min 14 sec
Total tests: run=40,542 failures=1 skipped=2,303
Total test files: run=461/463 failed=1 skipped=37 resource_denied=2 rerun=1
Result: FAILURE then FAILURE

It's not obvious that something was badly wrong in the re-run step.