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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`test_asyncio` `test_to_thread_concurrent` flaky","articleBody":"The `call_count` counter on `mock.Mock` is not atomic, so updates may be lost:\r\n\r\nhttps://github.com/python/cpython/blob/ab094d1b2b348f670743f88e52d1a3f2cab5abd5/Lib/test/test_asyncio/test_threads.py#L32-L41\r\n\r\nThis leads to occasional errors like:\r\n\r\n```\r\nFile \"Lib/test/test_asyncio/test_threads.py\", line 41, in test_to_thread_concurrent\r\nself.assertEqual(func.call_count, 10)\r\n~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^\r\nAssertionError: 9 != 10\r\n```\r\n\r\nI think the update is not actually atomic even with the GIL because of the use of `_delegating_property` in `Mock`, but I'm not entirely sure. The failures are definitely more likely to occur in the free-threaded build.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-124039\n* gh-124067\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/colesbury","@type":"Person","name":"colesbury"},"datePublished":"2024-08-12T19:22:00.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/122957/cpython/issues/122957"}