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Data race on adaptive counters with -X tlbc=0 in free threaded build #129752

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Data race on adaptive counters with -X tlbc=0 in free threaded build#129752
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corona10
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interpreter-core(Objects, Python, Grammar, and Parser dirs)topic-free-threadingtype-bugAn unexpected behavior, bug, or error

Description

@colesbury
colesbury
opened on Feb 6, 2025

Bug report

TSan reports data races for test_thread_local_bytecode.test_no_copies_if_tlbc_disabled.

WARNING: ThreadSanitizer: data race (pid=1222408)
  Read of size 2 at 0x7fffb44d7cc2 by thread T2:
    #0 _PyEval_EvalFrameDefault /raid/sgross/cpython/Python/generated_cases.c.h:7283:36 (python+0x402a47) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #1 _PyEval_EvalFrame /raid/sgross/cpython/./Include/internal/pycore_ceval.h:116:16 (python+0x3f48ea) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #2 _PyEval_Vector /raid/sgross/cpython/Python/ceval.c:1761:12 (python+0x3f48ea)
    #3 _PyFunction_Vectorcall /raid/sgross/cpython/Objects/call.c (python+0x1ef79f) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #4 _PyObject_VectorcallTstate /raid/sgross/cpython/./Include/internal/pycore_call.h:167:11 (python+0x1f3f9f) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #5 method_vectorcall /raid/sgross/cpython/Objects/classobject.c:72:20 (python+0x1f3f9f)
    #6 _PyVectorcall_Call /raid/sgross/cpython/Objects/call.c:273:16 (python+0x1ef413) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #7 _PyObject_Call /raid/sgross/cpython/Objects/call.c:348:16 (python+0x1ef413)
    #8 PyObject_Call /raid/sgross/cpython/Objects/call.c:373:12 (python+0x1ef495) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #9 thread_run /raid/sgross/cpython/./Modules/_threadmodule.c:354:21 (python+0x58d1d2) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #10 pythread_wrapper /raid/sgross/cpython/Python/thread_pthread.h:242:5 (python+0x4e89c7) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)

  Previous write of size 2 at 0x7fffb44d7cc2 by main thread:
    #0 _PyEval_EvalFrameDefault /raid/sgross/cpython/Python/generated_cases.c.h:7295:17 (python+0x402af4) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #1 _PyEval_EvalFrame /raid/sgross/cpython/./Include/internal/pycore_ceval.h:116:16 (python+0x3f48ea) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #2 _PyEval_Vector /raid/sgross/cpython/Python/ceval.c:1761:12 (python+0x3f48ea)
    #3 PyEval_EvalCode /raid/sgross/cpython/Python/ceval.c:662:21 (python+0x3f43fd) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #4 run_eval_code_obj /raid/sgross/cpython/Python/pythonrun.c:1331:9 (python+0x4c6e2e) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #5 run_mod /raid/sgross/cpython/Python/pythonrun.c:1406:19 (python+0x4c6b5f) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #6 _PyRun_StringFlagsWithName /raid/sgross/cpython/Python/pythonrun.c:1215:15 (python+0x4c3a75) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #7 _PyRun_SimpleStringFlagsWithName /raid/sgross/cpython/Python/pythonrun.c:548:15 (python+0x4c3a75)
    #8 pymain_run_command /raid/sgross/cpython/Modules/main.c:253:11 (python+0x502c21) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #9 pymain_run_python /raid/sgross/cpython/Modules/main.c:678:21 (python+0x502c21)
    #10 Py_RunMain /raid/sgross/cpython/Modules/main.c:766:5 (python+0x502c21)
    #11 pymain_main /raid/sgross/cpython/Modules/main.c:796:12 (python+0x5031b8) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #12 Py_BytesMain /raid/sgross/cpython/Modules/main.c:820:12 (python+0x50323b) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)
    #13 main /raid/sgross/cpython/./Programs/python.c:15:12 (python+0x16417b) (BuildId: d2c9a0e659ee21e3ff5331c41d7aa75d7fd2bc90)

The races are on the adaptive counter:

cpython/Python/generated_cases.c.h

Line 7283 in 365cf5f

uint16_t counter = read_u16(&this_instr[1].cache);

cpython/Python/generated_cases.c.h

Line 7295 in 365cf5f

ADVANCE_ADAPTIVE_COUNTER(this_instr[1].counter);

Linked PRs

Activity

  1. colesbury
    added
    topic-free-threading
    type-bugAn unexpected behavior, bug, or error
    on Feb 6, 2025
  2. colesbury
    added a commit that references this issue on Feb 6, 2025

    pythongh-117657: Add test_thread_local_bytecode to TSAN tests

    1555c9a
  3. picnixz
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)
    on Feb 7, 2025
  4. colesbury
    added 2 commits that reference this issue on Feb 10, 2025

    pythongh-117657: Add test_thread_local_bytecode to TSAN tests

    f9be7fa

    gh-117657: Add test_thread_local_bytecode to TSAN tests (gh-129753)

    1a8082a
  5. corona10
    added 4 commits that reference this issue on Aug 10, 2026

    pythongh-129752: Don't update adaptive counters when TLBC=0 in free-t…

    d644555

    gh-129752: Don't update adaptive counters when TLBC=0 in free-threadi…

    ee4fe00

    [3.14] pythongh-129752: Don't update adaptive counters when TLBC=0 in…

    befac58

    [3.14] gh-129752: Don't update adaptive counters when TLBC=0 in free-…

    c749534
  6. mbeijen
    added a commit that references this issue on Aug 14, 2026

    pythongh-129752: Don't update adaptive counters when TLBC=0 in free-t…

    b6bbc58
  7. hugovk
    added a commit that references this issue on Aug 26, 2026

    [3.15] gh-129752: Don't update adaptive counters when TLBC=0 in free-…

    d0484ab
  8. corona10
    closed this as completedon Aug 26, 2026
  9. corona10
    self-assigned this
    on Aug 26, 2026
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