BUG: data races in _buffer_get_info when multiple threads try to access buffer of ndarray #30648
Description
Describe the issue:
Run the reproducer using a TSAN instrumented build of CPython and numpy.
Reproduce the code example:
import numpy as np
from threading import Thread, Barrier
import inspect
import random
arr = np.array([1, 2, 3, 4, 5])
flags = [inspect.BufferFlags.STRIDED, inspect.BufferFlags.READ]
barrier = Barrier(4)
def func():
barrier.wait()
arr.__buffer__(random.choice(flags))
threads = [Thread(target=func) for _ in range(4)]
for t in threads:
t.start()
for t in threads:
t.join()Error message:
WARNING: ThreadSanitizer: data race (pid=6155)
Read of size 8 at 0x000128060100 by thread T1:
#0 _buffer_get_info <null> (_multiarray_umath.cpython-314t-darwin.so:arm64+0x37c1d8)
#1 array_getbuffer <null> (_multiarray_umath.cpython-314t-darwin.so:arm64+0x37c5b8)
#2 _PyMemoryView_FromBufferProc memoryobject.c:838 (libpython3.14t.dylib:arm64+0x122c1c)
#3 buffer typeobject.c:9688 (libpython3.14t.dylib:arm64+0x1a48b0)
#4 wrapperdescr_call descrobject.c:570 (libpython3.14t.dylib:arm64+0xa17ac)
#5 _PyObject_MakeTpCall call.c:242 (libpython3.14t.dylib:arm64+0x8a3ac)
#6 PyObject_Vectorcall call.c:327 (libpython3.14t.dylib:arm64+0x8af9c)
#7 _PyEval_EvalFrameDefault generated_cases.c.h:1619 (libpython3.14t.dylib:arm64+0x27cc00)
#8 _PyEval_Vector ceval.c:2083 (libpython3.14t.dylib:arm64+0x278928)
#9 _PyFunction_Vectorcall call.c (libpython3.14t.dylib:arm64+0x8b54c)
#10 method_vectorcall classobject.c:73 (libpython3.14t.dylib:arm64+0x8f9c0)
#11 context_run context.c:728 (libpython3.14t.dylib:arm64+0x2c3d18)
#12 method_vectorcall_FASTCALL_KEYWORDS descrobject.c:421 (libpython3.14t.dylib:arm64+0xa21cc)
#13 PyObject_Vectorcall call.c:327 (libpython3.14t.dylib:arm64+0x8af00)
#14 _PyEval_EvalFrameDefault generated_cases.c.h:1619 (libpython3.14t.dylib:arm64+0x27cc00)
#15 _PyEval_Vector ceval.c:2083 (libpython3.14t.dylib:arm64+0x278928)
#16 _PyFunction_Vectorcall call.c (libpython3.14t.dylib:arm64+0x8b54c)
#17 method_vectorcall classobject.c:73 (libpython3.14t.dylib:arm64+0x8f9c0)
#18 _PyObject_Call call.c:348 (libpython3.14t.dylib:arm64+0x8b1c0)
#19 PyObject_Call call.c:373 (libpython3.14t.dylib:arm64+0x8b234)
#20 thread_run _threadmodule.c:359 (libpython3.14t.dylib:arm64+0x419b3c)
#21 pythread_wrapper thread_pthread.h:242 (libpython3.14t.dylib:arm64+0x369a20)
Previous write of size 8 at 0x000128060100 by thread T4:
#0 _buffer_info_new <null> (_multiarray_umath.cpython-314t-darwin.so:arm64+0x37dc84)
#1 _buffer_get_info <null> (_multiarray_umath.cpython-314t-darwin.so:arm64+0x37c110)
#2 array_getbuffer <null> (_multiarray_umath.cpython-314t-darwin.so:arm64+0x37c5b8)
#3 _PyMemoryView_FromBufferProc memoryobject.c:838 (libpython3.14t.dylib:arm64+0x122c1c)
#4 buffer typeobject.c:9688 (libpython3.14t.dylib:arm64+0x1a48b0)
#5 wrapperdescr_call descrobject.c:570 (libpython3.14t.dylib:arm64+0xa17ac)
#6 _PyObject_MakeTpCall call.c:242 (libpython3.14t.dylib:arm64+0x8a3ac)
#7 PyObject_Vectorcall call.c:327 (libpython3.14t.dylib:arm64+0x8af9c)
#8 _PyEval_EvalFrameDefault generated_cases.c.h:1619 (libpython3.14t.dylib:arm64+0x27cc00)
#9 _PyEval_Vector ceval.c:2083 (libpython3.14t.dylib:arm64+0x278928)
#10 _PyFunction_Vectorcall call.c (libpython3.14t.dylib:arm64+0x8b54c)
#11 method_vectorcall classobject.c:73 (libpython3.14t.dylib:arm64+0x8f9c0)
#12 context_run context.c:728 (libpython3.14t.dylib:arm64+0x2c3d18)
#13 method_vectorcall_FASTCALL_KEYWORDS descrobject.c:421 (libpython3.14t.dylib:arm64+0xa21cc)
#14 PyObject_Vectorcall call.c:327 (libpython3.14t.dylib:arm64+0x8af00)
#15 _PyEval_EvalFrameDefault generated_cases.c.h:1619 (libpython3.14t.dylib:arm64+0x27cc00)
#16 _PyEval_Vector ceval.c:2083 (libpython3.14t.dylib:arm64+0x278928)
#17 _PyFunction_Vectorcall call.c (libpython3.14t.dylib:arm64+0x8b54c)
#18 method_vectorcall classobject.c:73 (libpython3.14t.dylib:arm64+0x8f9c0)
#19 _PyObject_Call call.c:348 (libpython3.14t.dylib:arm64+0x8b1c0)
#20 PyObject_Call call.c:373 (libpython3.14t.dylib:arm64+0x8b234)
#21 thread_run _threadmodule.c:359 (libpython3.14t.dylib:arm64+0x419b3c)
#22 pythread_wrapper thread_pthread.h:242 (libpython3.14t.dylib:arm64+0x369a20)
Thread T1 (tid=67013, running) created by main thread at:
#0 pthread_create <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x2f708)
#1 do_start_joinable_thread thread_pthread.h:289 (libpython3.14t.dylib:arm64+0x3686e0)
#2 PyThread_start_joinable_thread thread_pthread.h:331 (libpython3.14t.dylib:arm64+0x368528)
#3 do_start_new_thread _threadmodule.c:1868 (libpython3.14t.dylib:arm64+0x4196f0)
#4 thread_PyThread_start_joinable_thread _threadmodule.c:1991 (libpython3.14t.dylib:arm64+0x41847c)
#5 cfunction_call methodobject.c:564 (libpython3.14t.dylib:arm64+0x12d450)
#6 _PyObject_MakeTpCall call.c:242 (libpython3.14t.dylib:arm64+0x8a3ac)
#7 PyObject_Vectorcall call.c:327 (libpython3.14t.dylib:arm64+0x8af9c)
#8 _PyEval_EvalFrameDefault generated_cases.c.h:2959 (libpython3.14t.dylib:arm64+0x280794)
#9 PyEval_EvalCode ceval.c:975 (libpython3.14t.dylib:arm64+0x278504)
#10 run_mod pythonrun.c:1459 (libpython3.14t.dylib:arm64+0x347380)
#11 _PyRun_SimpleFileObject pythonrun.c:521 (libpython3.14t.dylib:arm64+0x342a5c)
#12 _PyRun_AnyFileObject pythonrun.c:81 (libpython3.14t.dylib:arm64+0x3421b0)
#13 pymain_run_file main.c:429 (libpython3.14t.dylib:arm64+0x383bb0)
#14 Py_RunMain main.c:775 (libpython3.14t.dylib:arm64+0x382fdc)
#15 pymain_main main.c:805 (libpython3.14t.dylib:arm64+0x383448)
#16 Py_BytesMain main.c:829 (libpython3.14t.dylib:arm64+0x38351c)
#17 main python.c:15 (python3.14:arm64+0x100000714)
Thread T4 (tid=67016, running) created by main thread at:
#0 pthread_create <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x2f708)
#1 do_start_joinable_thread thread_pthread.h:289 (libpython3.14t.dylib:arm64+0x3686e0)
#2 PyThread_start_joinable_thread thread_pthread.h:331 (libpython3.14t.dylib:arm64+0x368528)
#3 do_start_new_thread _threadmodule.c:1868 (libpython3.14t.dylib:arm64+0x4196f0)
#4 thread_PyThread_start_joinable_thread _threadmodule.c:1991 (libpython3.14t.dylib:arm64+0x41847c)
#5 cfunction_call methodobject.c:564 (libpython3.14t.dylib:arm64+0x12d450)
#6 _PyObject_MakeTpCall call.c:242 (libpython3.14t.dylib:arm64+0x8a3ac)
#7 PyObject_Vectorcall call.c:327 (libpython3.14t.dylib:arm64+0x8af9c)
#8 _PyEval_EvalFrameDefault generated_cases.c.h:3227 (libpython3.14t.dylib:arm64+0x28150c)
#9 PyEval_EvalCode ceval.c:975 (libpython3.14t.dylib:arm64+0x278504)
#10 run_mod pythonrun.c:1459 (libpython3.14t.dylib:arm64+0x347380)
#11 _PyRun_SimpleFileObject pythonrun.c:521 (libpython3.14t.dylib:arm64+0x342a5c)
#12 _PyRun_AnyFileObject pythonrun.c:81 (libpython3.14t.dylib:arm64+0x3421b0)
#13 pymain_run_file main.c:429 (libpython3.14t.dylib:arm64+0x383bb0)
#14 Py_RunMain main.c:775 (libpython3.14t.dylib:arm64+0x382fdc)
#15 pymain_main main.c:805 (libpython3.14t.dylib:arm64+0x383448)
#16 Py_BytesMain main.c:829 (libpython3.14t.dylib:arm64+0x38351c)
#17 main python.c:15 (python3.14:arm64+0x100000714)
SUMMARY: ThreadSanitizer: data race (_multiarray_umath.cpython-314t-darwin.so:arm64+0x37c1d8) in _buffer_get_info+0x154Python and NumPy Versions:
2.5.0.dev0+git20260114.a90ef57
3.14.2+ free-threading build (heads/3.14:c3fbe28, Dec 12 2025, 18:50:21) [Clang 17.0.0 (clang-1700.4.4.1)]
Runtime Environment:
[{'numpy_version': '2.5.0.dev0+git20260114.a90ef57',
'python': '3.14.2+ free-threading build (heads/3.14:c3fbe28, Dec 12 2025, '
'18:50:21) [Clang 17.0.0 (clang-1700.4.4.1)]',
'uname': uname_result(system='Darwin', node='Kumars-MacBook-Air.local', release='25.2.0', version='Darwin Kernel Version 25.2.0: Tue Nov 18 21:08:48 PST 2025; root:xnu-12377.61.12~1/RELEASE_ARM64_T8132', machine='arm64')},
{'simd_extensions': {'baseline': ['NEON', 'NEON_FP16', 'NEON_VFPV4', 'ASIMD'],
'found': ['ASIMDHP', 'ASIMDDP'],
'not_found': ['ASIMDFHM', 'SVE']}},
{'ignore_floating_point_errors_in_matmul': True}]
How does this issue affect you or how did you find it:
No response