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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"TSan: data race accessing socket fd","articleBody":"# Bug report\n\n### Bug description:\n\nThe `sock_fd` member in `PySocketSockObject` can be mutated while the socket is being used, for example when calling `socket.close` or `socket.detach`. However, some other threads can access that member without holding the GIL, and without using atomic instructions. This can trip up Thread Sanitizer in `test_asyncio`, for example:\n\n```\n0:00:31 load avg: 3.29 [15/52/1] test_asyncio.test_sock_lowlevel worker non-zero exit code (Exit code 66)\n==================\nWARNING: ThreadSanitizer: data race (pid=7227)\n  Write of size 4 at 0x7fd903611570 by thread T19:\n    #0 sock_close /home/runner/work/cpython/cpython/./Modules/socketmodule.c:3339:20 (_socket.cpython-313d-x86_64-linux-gnu.so+0xdbde) (BuildId: 7a12da96172d453cd023792c027755908db49f4e)\n[...]\n\n  Previous read of size 4 at 0x7fd903611570 by main thread:\n    #0 sock_sendto_impl /home/runner/work/cpython/cpython/./Modules/socketmodule.c:4474:29 (_socket.cpython-313d-x86_64-linux-gnu.so+0x131e5) (BuildId: 7a12da96172d453cd023792c027755908db49f4e)\n    #1 sock_call_ex /home/runner/work/cpython/cpython/./Modules/socketmodule.c:968:19 (_socket.cpython-313d-x86_64-linux-gnu.so+0x10fa1) (BuildId: 7a12da96172d453cd023792c027755908db49f4e)\n    #2 sock_call /home/runner/work/cpython/cpython/./Modules/socketmodule.c:1020:12 (_socket.cpython-313d-x86_64-linux-gnu.so+0xf1a1) (BuildId: 7a12da96172d453cd023792c027755908db49f4e)\n    #3 sock_sendto /home/runner/work/cpython/cpython/./Modules/socketmodule.c:4532:9 (_socket.cpython-313d-x86_64-linux-gnu.so+0xf1a1)\n[...]\n```\n\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux","author":{"url":"https://github.com/pitrou","@type":"Person","name":"pitrou"},"datePublished":"2024-03-16T15:52:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/116912/cpython/issues/116912"}