Feature or enhancement

We need to make the TSAN tests pass with the GIL disabled before we can disable the GIL by default in free-threaded builds.

This should proceed in two phases:

1. Add suppressions for existing TSAN warnings.
2. Triage, fix, and remove the suppressions for the warnings enumerated in (1).

How to run the TSAN tests

1. Build with TSAN:
   env CC=clang CXX=clang++ ./configure --disable-gil --with-thread-sanitizer --with-pydebug && make -j
2. Run tests:
   env TSAN_OPTIONS=suppressions=<repo_root>/Tools/tsan/suppressions_free_threading.txt ./python -m test --tsan -j4

Working on a race

1. Verify that the TSAN tests are passing using the steps from above.
2. Pick a suppression from the section below and assign it to yourself (edit it and add your username next to it). Some of them may be related. If you find that other suppressions are related to the race you're working on please assign them to yourself or contact their owner if they're already assigned.
3. Delete the suppression from<repo_root>/Tools/tsan/suppressions_free_threading.txt, run the TSAN tests, and verify that the race is reported by TSAN. You may need to comment out unrelated functions (notably,_PyEval_EvalFrameDefault) in order to reproduce the race.
4. Fix the race.

Suppressions

### Tasks- [ ] PyInterpreterState_ThreadHead- [ ] PyThreadState_Clear- [ ] PyThreadState_Next- [ ] PyUnstable_InterpreterFrame_GetLine- [ ] _PyFrame_GetCode- [ ] _PyFrame_Initialize- [ ] _PyObject_TryGetInstanceAttribute- [ ] _Py_slot_tp_getattr_hook- [x] _multiprocessing_SemLock_acquire_impl- [x] _multiprocessing_SemLock_release_impl- [ ] add_threadstate- [ ] assign_version_tag- [ ] dump_traceback- [ ] fatal_error- [ ] free_threadstate- [ ] list_get_item_ref- [x] new_reference- [ ] pthread_create- [ ] set_default_allocator_unlocked- [ ] tstate_delete_common- [ ] tstate_is_freed- [ ] type_modified_unlocked- [ ] write_thread_id

Linked PRs

• gh-117657: Add TSAN suppressions for the free-threaded build #117736
• gh-117657: Quiet TSAN warning about a data race betweenstart_the_world() andtstate_try_attach() #117828
• gh-117657: Quiet more TSAN warnings due to incorrect modeling of compare/exchange #117830
• gh-117657: Fix data races in the method cache in free-threaded builds #117954
• gh-117657: Quiet erroneous TSAN reports of data races in_PySeqLock #117955
• gh-117657: Fix small issues with instrumentation and TSAN #118064
• gh-117657: use relaxed loads for checking dict keys immortality #118067
• [gh-117657] _Py_MergeZeroLocalRefcount isn't loading ob_ref_shared with strong enough semantics #118111
• gh-117657: Quiet TSAN warnings about remaining non-atomic accesses oftstate->state #118165
• gh-117657: Fixes a few small TSAN issues in dictobject #118200
• [gh-117657] Fix some issues with TSAN in typeobject #118249
• gh-117657: Add a couple more TSAN suppressions #118256
• gh-117657: Fix race data race in_Py_IsOwnedByCurrentThread() #118258
• gh-117657: Fix TSAN list set failure #118260
• gh-117657: Fix data race in_Py_IsImmortal #118261
• gh-117657: Fix data races when writing / readingob_gc_bits #118292
• gh-117657: Disable the function/code cache in free-threaded builds #118301
• gh-117657: TSAN fix race on gstate->young.count #118313
• gh-117657: Don't specialize RESUME_CHECK when specialization is disabled #118349
• gh-117657: Fix TSAN race involving import lock #118523
• gh-117657: Use clang 18 in TSAN builds #118533
• gh-117657: Replace TSAN suppresions with more specific rules #118722
• gh-117657: Log TSAN warnings to separate files and archive them #118747
• gh-117657: initialize_new_array #118769
• [3.13] gh-117657: Fix data races when writing / readingob_gc_bits (GH-118292) #118796
• gh-117657: Acquire a critical section aroundSemLock.__{enter,exit}__ #118812
• gh-117657: initialize_new_array remove race #118842
• gh-117657: Fix QSBR race condition #118843
• [3.13] gh-117657: Acquire a critical section aroundSemLock.__{enter,exit}__ (GH-118812) #118856
• gh-117657: Fix data races reported by TSAN oninterp->threads.main #118865
• [3.13] gh-117657: Replace TSAN suppresions with more specific rules (GH-118722) #118870
• [3.13] gh-117657: Fix data races reported by TSAN oninterp->threads.main (GH-118865) #118904
• [3.13] gh-117657: Fix QSBR race condition (GH-118843) #118905
• [3.13] gh-117657: Log TSAN warnings to separate files and archive them (GH-118747) #118931
• gh-117657: Fix itertools.count thread safety #119267
• gh-117657: Fix itertools.count thread safety #119268
• gh-117657: Fix missing atomic in dict_resize #119312
• gh-117657: TSAN Fix race inPyMember_Get andPyMember_Set, forPy_T_OBJECT_EX type #119368
• [3.13] gh-117657: Fix missing atomic in dict_resize #119416
• [3.13] gh-117657: Fix missing atomic in dict_resize (GH-119312) #119417
• gh-117657: Fix TSAN race in free-threaded GC #119883
• gh-117657: Fix TSAN race in QSBR assertion #119887
• [3.13] gh-117657: Fix TSAN race in free-threaded GC (GH-119883) #119903
• [3.13] gh-117657: Fix TSAN race in QSBR assertion (GH-119887) #119904
• gh-117657: Fix data races report by TSAN unicode-hash #119907
• gh-117657: Add TSAN suppression forset_discard_entry #119908
• [3.13] gh-117657: Add TSAN suppression forset_discard_entry (GH-119908) #119914
• gh-117657: Avoidsem_clockwait in TSAN #119915
• gh-117657: Fix TSAN reported race in_PyEval_IsGILEnabled. #119921
• gh-117657: Fix race involving GC and heap initialization #119923
• gh-117657: Fix race involving immortalizing objects #119927
• [3.13] gh-117657: Fix TSAN reported race in_PyEval_IsGILEnabled. (GH-119921) #119939
• [3.13] gh-117657: Avoidsem_clockwait in TSAN (GH-119915) #119992
• [3.13] gh-117657: Fix race involving immortalizing objects (GH-119927) #120005
• [3.13] gh-117657: Fix itertools.count thread safety (GH-119268) #120007
• [3.13] gh-117657: Fix race involving GC and heap initialization (GH-119923) #120038
• gh-117657: Fix some simple races in instrumentation.c #120118
• gh-117657: Make Py_TYPE and Py_SET_TYPE thread safe #120165
• [3.13] gh-117657: Fix TSAN race involving import lock (GH-118523) #120169
• gh-117657: Fix TSan reported data race on ioctl_works #120175
• gh-117657: Make PyType_HasFeature atomic #120210
• [3.13] gh-117657: Make Py_TYPE and Py_SET_TYPE thread safe (GH-120165) #120403
• [3.13] gh-117657: Make PyType_HasFeature atomic (GH-120210) #120443
• [3.13] gh-117657: Fix some simple races in instrumentation.c (GH-120118) #120444
• gh-117657: Fix data races for set_inheritable in fileutils.c with free-threaded builds #120458
• gh-117657: Make PyType_HasFeature (exported version) atomic #120484
• gh-117657: Using critical section to make _socket.socket.close thread safe #120490
• gh-117657: Add TSAN suppression for set_default_allocator_unlocked #120500
• [3.13] gh-117657: Add TSAN suppression for set_default_allocator_unlocked (GH-120500) #120510
• gh-117657: Make frame clearing thread-safe #120542
• [3.13] gh-117657: Make PyType_HasFeature (exported version) atomic (GH-120484) #120554
• gh-117657: Move static variables in fileutils.c to thread state #120559
• [3.13] gh-117657: Fix TSan reported data race on ioctl_works (GH-120175) #120654
• [3.13] gh-117657: Fix__slots__ thread safety in free-threaded build (GH-119368) #120655
• gh-117657: Enable TSAN check on macOS with free-threads build #120502
• gh-117657: Fix data races reported by TSAN in some set methods #120914
• [3.13] gh-117657: Fix data races reported by TSAN in some set methods (GH-120914) #121240
• gh-117657: Remove TSAN suppressions for _abc.c #121508
• gh-117657: Fix TSAN races in setobject.c #121511
• [3.13] gh-117657: Fix TSAN races in setobject.c (GH-121511) #121541
• gh-117657: Skip test when running under TSan #121549
• gh-117657: Fix TSan race in _PyDict_CheckConsistency #121551
• [3.13] gh-117657: Skip test when running under TSan (GH-121549) #121553
• [3.13] gh-117657: Fix TSan race in _PyDict_CheckConsistency (GH-121551) #121590
• [3.13] gh-117657: Remove TSAN suppressions for _abc.c (GH-121508) #121598
• gh-117657: Skip tests that fork with threads under TSan #121599
• gh-117657: Fix some races in tracebacks #121748
• [3.13] gh-117657: Skip tests that fork with threads under TSan (GH-121599) #121819
• gh-117657: Avoid race inPAUSE_ADAPTIVE_COUNTER in free-threaded build #122190
• gh-117657: Skip tests that use threads after fork #122194
• [3.13] gh-117657: Skip tests that use threads after fork (GH-122194) #122198
• [3.13] gh-117657: Avoid race inPAUSE_ADAPTIVE_COUNTER in free-threaded build (GH-122190) #122475
• gh-117657: TSAN Fix races inPyMember_Get andPyMember_Set, for C extensions #123211
• gh-117657: fix race:sock_recv_impl suppressions for free-thread building #123697
• gh-117657: remove dump_traceback suppression from list #123871
• gh-117657: Use an atomic store to set type flags. #127588
• gh-117657: Fix data race in new_reference for free-threaded build #129665
• gh-117657: Include all of test_free_threading in TSAN tests #129749
• gh-117657: Skip tests that may cause stack overflows under TSan #129751
• gh-117657: Add test_thread_local_bytecode to TSAN tests #129753
• gh-117657: Fix data race indict_dict_merge #129755
• [3.13] gh-117657: Fix data race indict_dict_merge (gh-129755) #129808
• gh-117657: Enable test_opcache under TSAN #129831
• [3.13] gh-117657: Enable test_opcache under TSAN (GH-129831) #130597
• gh-117657: Skip some tests when running with TSAN #131555
• gh-117657: Fix TSAN data race in _PyEval_SetTrace assertion #131561
• [3.13] gh-117657: Fix TSAN data race in _PyEval_SetTrace assertion (gh-131561) #131564
• gh-117657: Fix data race incompare_unicode_unicode_threadsafe #131746
• gh-117657: enabletest_capi under TSAN #136269