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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"test_hashlib fails when run on Free Threading with TSAN","articleBody":"# Crash report\n\nTSAN CI job: https://github.com/python/cpython/actions/runs/28747943876/job/85377269260?pr=152717\n\ntest_hashlib fails when run on Free Threading with TSAN on the main branch.\n\nCommands:\n\n```\nexport CC=clang\nexport TSAN_OPTIONS=\"$PWD/log_path=san_log suppressions=$PWD/Tools/tsan/suppressions_free_threading.txt handle_segv=0\"\n\n./configure --config-cache --with-thread-sanitizer --with-pydebug --disable-gil\nmake -j4\n./python -m test --tsan-parallel --parallel-threads=4 -j4 -W --timeout=600 --slowest\n```\n\nTests output (truncated):\n\n```\nUsing random seed: 1463135961\n0:00:00 load avg: 2.65 mem: 267.1 MiB Run 2 tests in parallel using 2 worker processes (timeout: 10 min, worker timeout: 15 min)\n0:00:06 load avg: 2.76 mem: 611.2 MiB [1/2] test_abc passed\n0:00:14 load avg: 2.78 mem: 278.3 MiB [2/2/1] test_hashlib worker non-zero exit code (Exit code 66)\ntest_algorithms_available (test.test_hashlib.HashLibTestCase.test_algorithms_available) [threads=4] ... ok\ntest_algorithms_guaranteed (test.test_hashlib.HashLibTestCase.test_algorithms_guaranteed) [threads=4] ... ok\n(...)\ntest_scrypt_types (test.test_hashlib.TestScrypt.test_scrypt_types) [threads=4] ... ok\ntest_scrypt_validate (test.test_hashlib.TestScrypt.test_scrypt_validate) [threads=4] ... ok\n\n----------------------------------------------------------------------\nRan 88 tests in 9.698s\n\nOK (skipped=56)\n\n== Tests result: FAILURE ==\n```\n\nTSAN logs (truncated):\n\n```\nWARNING: ThreadSanitizer: data race (pid=30628)\n  Read of size 8 at 0x721c0000e3a8 by thread T456:\n    #0 memcmp \u003cnull\u003e (python+0x10d49e) (BuildId: 5899a6ff881ea0db9e292325f4f3bbeaba9715e6)\n    #1 \u003cnull\u003e \u003cnull\u003e (libcrypto.so.3+0x24f2d1) (BuildId: 6608be85412b580cc4873b0421a014a9cc2a7b41)\n    #2 pbkdf2_hmac /home/runner/work/cpython/cpython/./Modules/clinic/_hashopenssl.c.h:1490:20 (_hashlib.cpython-316td-x86_64-linux-gnu.so+0x7299) (BuildId: 1c2fdd533a623cb5e65ca60ec9662a58487ffb8b)\n\n  Previous write of size 8 at 0x721c0000e3a8 by thread T454 (mutexes: write M0, write M1):\n    #0 memcpy \u003cnull\u003e (python+0xfc022) (BuildId: 5899a6ff881ea0db9e292325f4f3bbeaba9715e6)\n    #1 \u003cnull\u003e \u003cnull\u003e (libcrypto.so.3+0x24f0e6) (BuildId: 6608be85412b580cc4873b0421a014a9cc2a7b41)\n    #2 pbkdf2_hmac /home/runner/work/cpython/cpython/./Modules/clinic/_hashopenssl.c.h:1490:20 (_hashlib.cpython-316td-x86_64-linux-gnu.so+0x7299) (BuildId: 1c2fdd533a623cb5e65ca60ec9662a58487ffb8b)\n\n  Mutex M0 (0x721000000500) created at:\n    #0 pthread_rwlock_init \u003cnull\u003e (python+0x103e6e) (BuildId: 5899a6ff881ea0db9e292325f4f3bbeaba9715e6)\n    #1 CRYPTO_THREAD_lock_new \u003cnull\u003e (libcrypto.so.3+0x275485) (BuildId: 6608be85412b580cc4873b0421a014a9cc2a7b41)\n    #2 CRYPTO_THREAD_run_once \u003cnull\u003e (libcrypto.so.3+0x27556c) (BuildId: 6608be85412b580cc4873b0421a014a9cc2a7b41)\n    #3 run_exec_func /home/runner/work/cpython/cpython/Objects/moduleobject.c:707:15 (python+0x374a4a) (BuildId: 5899a6ff881ea0db9e292325f4f3bbeaba9715e6)\n\n  Mutex M1 (0x7210000008c0) created at:\n    #0 pthread_rwlock_init \u003cnull\u003e (python+0x103e6e) (BuildId: 5899a6ff881ea0db9e292325f4f3bbeaba9715e6)\n    #1 CRYPTO_THREAD_lock_new \u003cnull\u003e (libcrypto.so.3+0x275485) (BuildId: 6608be85412b580cc4873b0421a014a9cc2a7b41)\n    #2 CRYPTO_THREAD_run_once \u003cnull\u003e (libcrypto.so.3+0x27556c) (BuildId: 6608be85412b580cc4873b0421a014a9cc2a7b41)\n    #3 run_exec_func /home/runner/work/cpython/cpython/Objects/moduleobject.c:707:15 (python+0x374a4a) (BuildId: 5899a6ff881ea0db9e292325f4f3bbeaba9715e6)\n```\n\nFull TSAN logs: [tsan_full.log](https://github.com/user-attachments/files/29707099/tsan_full.log).","author":{"url":"https://github.com/vstinner","@type":"Person","name":"vstinner"},"datePublished":"2026-07-06T14:26:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/153201/cpython/issues/153201"}