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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"An interpreter can start running during `_interpreters.destroy`","articleBody":"# Crash report\n\n### What happened?\n\nNow that gh-126914 is out of the way, we can try and deal with some of the other issues related to multithreading and subinterpreters that couldn't get dealt with before. Namely, the `is_running_main` inside `_interpreters.destroy` doesn't account for the fact that the interpreter could start running again by another thread *after* that check has already passed.\n\nQuick reproducer:\n\n```python\nfrom threading import Thread\nimport _interpreters\n\ninterp = _interpreters.create()\n\n\ndef run():\n    _interpreters.run_string(interp, \"1\")\n    _interpreters.destroy(interp)\n\n\nthreads = [Thread(target=run) for _ in range(1000)]\nfor thread in threads:\n    thread.start()\n\nfor thread in threads:\n    thread.join()\n```\n\nI think the simplest fix would be to just disallow a subinterpreter from ever set \"running main\" again after that check has finished. I implemented this already in the (closed) gh-126696, but I'd like to try and refactor that a bit before just copying things over to a new PR.\n\ncc @ericsnowcurrently, let me know if you have a better approach.\n\n### CPython versions tested on:\n\n3.13, 3.14, CPython main branch\n\n### Operating systems tested on:\n\nLinux\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-127044\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/ZeroIntensity","@type":"Person","name":"ZeroIntensity"},"datePublished":"2024-11-19T21:21:39.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/127041/cpython/issues/127041"}