René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"_PySemaphore_Wakeup: parking_lot: ReleaseSemaphore failed","articleBody":"# Crash report\n\n### What happened?\n\nThere might be a bunch of other code wrapping around this, and this doesn't always reproduce it.\n\n\u003cdetails\u003e\u003csummary\u003eDetails\u003c/summary\u003e\n\u003cp\u003e\n\n\n```python\nimport trio\nimport signal\nimport threading\n\ndef run_in_trio_thread_ki_inner() -\u003e None:\n    # if we get a control-C during a run_in_trio_thread, then it propagates\n    # back to the caller (slick!)\n    record = set()\n\n    async def check_run_in_trio_thread() -\u003e None:\n        token = trio.lowlevel.current_trio_token()\n\n        def trio_thread_fn() -\u003e None:\n            print(\"in Trio thread\")\n            assert not trio.lowlevel.currently_ki_protected()\n            print(\"ki_self\")\n            try:\n                signal.raise_signal(signal.SIGINT)\n            finally:\n                import sys\n\n                print(\"finally\", sys.exc_info())\n\n        async def trio_thread_afn() -\u003e None:\n            trio_thread_fn()\n\n        def external_thread_fn() -\u003e None:\n            try:\n                print(\"running\")\n                trio.from_thread.run_sync(trio_thread_fn, trio_token=token)\n            except KeyboardInterrupt:\n                print(\"ok1\")\n                record.add(\"ok1\")\n            try:\n                trio.from_thread.run(trio_thread_afn, trio_token=token)\n            except KeyboardInterrupt:\n                print(\"ok2\")\n                record.add(\"ok2\")\n\n        thread = threading.Thread(target=external_thread_fn)\n        thread.start()\n        print(\"waiting\")\n        while thread.is_alive():  # noqa: ASYNC110\n            await trio.sleep(0.01)  # Fine to poll in tests.\n        print(\"waited, joining\")\n        thread.join()\n        print(\"done\")\n\n    trio.run(check_run_in_trio_thread)\n    assert record == {\"ok1\", \"ok2\"}\n\nrun_in_trio_thread_ki_inner()\n```\n\n\u003c/p\u003e\n\u003c/details\u003e \n\nHere's an example from logs: https://github.com/A5rocks/trio/actions/runs/24711139448/job/72275846322#step:4:1174 providing this stack trace:\n```\nFatal Python error: _PySemaphore_Wakeup: parking_lot: ReleaseSemaphore failed\nPython runtime state: initialized\n\nStack (most recent call first):\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_io_windows.py\", line 325 in _get_underlying_socket\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_io_windows.py\", line 360 in _get_base_socket\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_io_windows.py\", line 737 in _afd_poll\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_io_windows.py\", line 779 in wait_readable\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_generated_io_windows.py\", line 61 in wait_readable\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_wakeup_socketpair.py\", line 42 in wait_woken\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_entry_queue.py\", line 101 in task\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_run.py\", line 2867 in unrolled_run\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_run.py\", line 2533 in run\n  File \"D:\\a\\trio\\trio\\empty\\repro.py\", line 49 in run_in_trio_thread_ki_inner\n  File \"D:\\a\\trio\\trio\\empty\\repro.py\", line 52 in \u003cmodule\u003e\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\execfile.py\", line 213 in run\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\cmdline.py\", line 1042 in do_run\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\cmdline.py\", line 853 in command_line\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\cmdline.py\", line 1163 in main\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Scripts\\coverage.exe\\__main__.py\", line 10 in \u003cmodule\u003e\n  File \"\u003cfrozen runpy\u003e\", line 88 in _run_code\n  File \"\u003cfrozen runpy\u003e\", line 198 in _run_module_as_main\n\nExtension modules: _cffi_backend (total: 1)\n```\n\nHere's another example! https://github.com/A5rocks/trio/actions/runs/24711139448/job/72275846557#step:4:1225 with these logs:\n```\nFatal Python error: _PySemaphore_Wakeup: parking_lot: ReleaseSemaphore failed\nPython runtime state: initialized\n\nStack (most recent call first):\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\bytecode.py\", line 83 in bytes_to_lines\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\sysmon.py\", line 350 in sysmon_py_start\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_run.py\", line 2012 in task_exited\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_run.py\", line 2890 in unrolled_run\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\trio\\_core\\_run.py\", line 2533 in run\n  File \"D:\\a\\trio\\trio\\empty\\repro.py\", line 49 in run_in_trio_thread_ki_inner\n  File \"D:\\a\\trio\\trio\\empty\\repro.py\", line 52 in \u003cmodule\u003e\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\execfile.py\", line 213 in run\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\cmdline.py\", line 1042 in do_run\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\cmdline.py\", line 853 in command_line\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Lib\\site-packages\\coverage\\cmdline.py\", line 1163 in main\n  File \"C:\\hostedtoolcache\\windows\\Python\\3.14.4\\x64-freethreaded\\Scripts\\coverage.exe\\__main__.py\", line 10 in \u003cmodule\u003e\n  File \"\u003cfrozen runpy\u003e\", line 88 in _run_code\n  File \"\u003cfrozen runpy\u003e\", line 198 in _run_module_as_main\n\nExtension modules: _cffi_backend (total: 1)\n```\n\nAlso note that this requires a) freethreading and b) specifically the Windows x64 build. (maybe this reproduces on other builds too, but I haven't seen it.)\n\n### CPython versions tested on:\n\n3.14\n\n### Operating systems tested on:\n\n_No response_\n\n### Output from running 'python -VV' on the command line:\n\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-148847\n* gh-148852\n* gh-148884\n* gh-148885\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/A5rocks","@type":"Person","name":"A5rocks"},"datePublished":"2026-04-21T07:54:07.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/148820/cpython/issues/148820"}