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Data race in gc_collect_internal on gcstate->last_mem #134801
Description
Bug report
Bug description:
Races assigning to __dict__ should be thread safe ... ==================
WARNING: ThreadSanitizer: data race (pid=3951040)
Write of size 8 at 0x555555f78438 by thread T60:
#0 gc_collect_internal /home/sgross/cpython/Python/gc_free_threading.c:2248:30 (python+0x59a09e) (BuildId: 29173f71c99127c1e5ec9850aea4c8892a29468f)
#1 gc_collect_main /home/sgross/cpython/Python/gc_free_threading.c:2313:5 (python+0x595027) (BuildId: 29173f71c99127c1e5ec9850aea4c8892a29468f)
#2 _Py_RunGC /home/sgross/cpython/Python/gc_free_threading.c:2762:5 (python+0x595bd5) (BuildId: 29173f71c99127c1e5ec9850aea4c8892a29468f)
#3 _Py_HandlePending /home/sgross/cpython/Python/ceval_gil.c:1395:9 (python+0x5aa283) (BuildId: 29173f71c99127c1e5ec9850aea4c8892a29468f)
...
Previous read of size 8 at 0x555555f78438 by thread T62:
#0 gc_should_collect_mem_usage /home/sgross/cpython/Python/gc_free_threading.c:2065:36 (python+0x596f36) (BuildId: 29173f71c99127c1e5ec9850aea4c8892a29468f)
#1 gc_should_collect /home/sgross/cpython/Python/gc_free_threading.c:2103:12 (python+0x596f36)
#2 record_allocation /home/sgross/cpython/Python/gc_free_threading.c:2120:13 (python+0x595b08) (BuildId: 29173f71c99127c1e5ec9850aea4c8892a29468f)
#3 _PyObject_GC_Link /home/sgross/cpython/Python/gc_free_threading.c:2753:5 (python+0x595b08)
cc @nascheme
CPython versions tested on:
CPython main branch
Operating systems tested on:
No response
Activity
kumaraditya303 commentedon May 27, 2025
I already have a fix at #134692