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BUG: fix thread safety of array_getbuffer (#30667) #30736

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Merged
charris merged 2 commits into from
Jan 27, 2026
Merged

BUG: fix thread safety of array_getbuffer (#30667) #30736

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127235f
BUG: fix thread safety of `array_getbuffer` (#30667)
kumaraditya303 Jan 27, 2026
431fffb
MAINT: Skip tests that require __buffer__.
charris Jan 27, 2026
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7 changes: 6 additions & 1 deletion numpy/_core/src/multiarray/buffer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -793,8 +793,10 @@ array_getbuffer(PyObject *obj, Py_buffer *view, int flags)
}

/* Fill in information (and add it to _buffer_info if necessary) */
Py_BEGIN_CRITICAL_SECTION(self);
info = _buffer_get_info(
&((PyArrayObject_fields *)self)->_buffer_info, obj, flags);
Py_END_CRITICAL_SECTION();
if (info == NULL) {
goto fail;
}
Expand Down Expand Up @@ -880,7 +882,10 @@ void_getbuffer(PyObject *self, Py_buffer *view, int flags)
* to find the correct format. This format must also be stored, since
* at least in theory it can change (in practice it should never change).
*/
_buffer_info_t *info = _buffer_get_info(&scalar->_buffer_info, self, flags);
_buffer_info_t *info = NULL;
Py_BEGIN_CRITICAL_SECTION(scalar);
info = _buffer_get_info(&scalar->_buffer_info, self, flags);
Py_END_CRITICAL_SECTION();
if (info == NULL) {
Py_DECREF(self);
return -1;
Expand Down
29 changes: 29 additions & 0 deletions numpy/_core/tests/test_multithreading.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import concurrent.futures
import sys
import threading

import pytest
Expand Down Expand Up @@ -375,3 +376,31 @@ def replace_list_items(b):
finally:
if len(tasks) < 5:
b.abort()

@pytest.mark.skipif(sys.version_info < (3, 12), reason="Python >= 3.12 required")
def test_array__buffer__thread_safety():
import inspect
arr = np.arange(1000)
flags = [inspect.BufferFlags.STRIDED, inspect.BufferFlags.READ]

def func(b):
b.wait()
for i in range(100):
arr.__buffer__(flags[i % 2])

run_threaded(func, max_workers=8, pass_barrier=True)

@pytest.mark.skipif(sys.version_info < (3, 12), reason="Python >= 3.12 required")
def test_void_dtype__buffer__thread_safety():
import inspect
dt = np.dtype([('name', np.str_, 16), ('grades', np.float64, (2,))])
x = np.array(('ndarray_scalar', (1.2, 3.0)), dtype=dt)[()]
assert isinstance(x, np.void)
flags = [inspect.BufferFlags.STRIDES, inspect.BufferFlags.READ]

def func(b):
b.wait()
for i in range(100):
x.__buffer__(flags[i % 2])

run_threaded(func, max_workers=8, pass_barrier=True)
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