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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"multiprocessing child segfault when passing lock as an argument","articleBody":"# Crash report\r\n\r\n### What happened?\r\n\r\nIt seems that the below code will serialize the pointer to the lock handle over to the child process, and then rebuild the raw pointer in https://github.com/python/cpython/blob/main/Modules/_multiprocessing/clinic/semaphore.c.h#L331\r\n\r\nthis then segfaults the child process - which seems to cause new children to spin up.\r\n\r\n\r\n```python\r\nimport multiprocessing\r\nimport os\r\n\r\ndef _init(l):\r\n    print(os.getpid())\r\n    print(l)\r\n\r\ndef main():\r\n    ctx = multiprocessing.get_context(method=\"spawn\")\r\n    lock = multiprocessing.Lock()\r\n    with ctx.Pool(1, initializer=_init, initargs=(lock,)) as pool:\r\n        ret = pool.map(print, [1])\r\n\r\nif __name__ == \"__main__\":\r\n    main()\r\n```\r\n\r\n\r\n### CPython versions tested on:\r\n\r\n3.10, 3.11\r\n\r\n### Operating systems tested on:\r\n\r\nLinux\r\n\r\n### Output from running 'python -VV' on the command line:\r\n\r\n_No response_","author":{"url":"https://github.com/DylanZA","@type":"Person","name":"DylanZA"},"datePublished":"2024-05-22T16:46:39.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/119413/cpython/issues/119413"}