https://github.com/python/cpython/commit/e6c3039cb39e68ae9af9ddcaca341c5af8f9cf23
commit: e6c3039cb39e68ae9af9ddcaca341c5af8f9cf23
branch: main
author: Peter Bierma <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2025-06-12T16:41:05+05:30
summary:
gh-135410: use a critical section around `StringIO.__next__` (#135412)
files:
A Misc/NEWS.d/next/Library/2025-06-11-19-05-49.gh-issue-135410.E89Boi.rst
M Lib/test/test_memoryio.py
M Modules/_io/stringio.c
diff --git a/Lib/test/test_memoryio.py b/Lib/test/test_memoryio.py
index 63998a86c45b53..249e0f3ba32f29 100644
--- a/Lib/test/test_memoryio.py
+++ b/Lib/test/test_memoryio.py
@@ -5,6 +5,7 @@
import unittest
from test import support
+from test.support import threading_helper
import gc
import io
@@ -12,6 +13,7 @@
import pickle
import sys
import weakref
+import threading
class IntLike:
def __init__(self, num):
@@ -723,6 +725,22 @@ def test_newline_argument(self):
for newline in (None, "", "\n", "\r", "\r\n"):
self.ioclass(newline=newline)
+ @unittest.skipUnless(support.Py_GIL_DISABLED, "only meaningful under
free-threading")
+ @threading_helper.requires_working_threading()
+ def test_concurrent_use(self):
+ memio = self.ioclass("")
+
+ def use():
+ memio.write("x" * 10)
+ memio.readlines()
+
+ threads = [threading.Thread(target=use) for _ in range(8)]
+ with threading_helper.catch_threading_exception() as cm:
+ with threading_helper.start_threads(threads):
+ pass
+
+ self.assertIsNone(cm.exc_value)
+
class PyStringIOTest(MemoryTestMixin, MemorySeekTestMixin,
TextIOTestMixin, unittest.TestCase):
@@ -890,6 +908,7 @@ def test_setstate(self):
self.assertRaises(ValueError, memio.__setstate__, ("closed", "", 0,
None))
+
class CStringIOPickleTest(PyStringIOPickleTest):
UnsupportedOperation = io.UnsupportedOperation
diff --git
a/Misc/NEWS.d/next/Library/2025-06-11-19-05-49.gh-issue-135410.E89Boi.rst
b/Misc/NEWS.d/next/Library/2025-06-11-19-05-49.gh-issue-135410.E89Boi.rst
new file mode 100644
index 00000000000000..a5917fba3f7bb9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-06-11-19-05-49.gh-issue-135410.E89Boi.rst
@@ -0,0 +1,2 @@
+Fix a crash when iterating over :class:`io.StringIO` on the :term:`free
+threaded <free threading>` build.
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index 56913fafefba8b..8482c268176c5b 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -404,7 +404,7 @@ _io_StringIO_readline_impl(stringio *self, Py_ssize_t size)
}
static PyObject *
-stringio_iternext(PyObject *op)
+stringio_iternext_lock_held(PyObject *op)
{
PyObject *line;
stringio *self = stringio_CAST(op);
@@ -441,6 +441,16 @@ stringio_iternext(PyObject *op)
return line;
}
+static PyObject *
+stringio_iternext(PyObject *op)
+{
+ PyObject *res;
+ Py_BEGIN_CRITICAL_SECTION(op);
+ res = stringio_iternext_lock_held(op);
+ Py_END_CRITICAL_SECTION();
+ return res;
+}
+
/*[clinic input]
@critical_section
_io.StringIO.truncate
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