[pull] main from python:main

Include/internal/pycore_lock.h

@@ -34,6 +34,11 @@ _PyMutex_at_fork_reinit(PyMutex *m)
 
 typedef enum _PyLockFlags {
     // Do not detach/release the GIL when waiting on the lock.
+    //
+    // Note that code executed while holding a mutex with this flag must
+    // not detach, reach a safepoint or initiate a stop-the-world pause.
+    // Otherwise, a non-detaching waiter may remain waiting for this mutex and
+    // prevent the pause from completing.
     _Py_LOCK_DONT_DETACH = 0,
 
     // Detach/release the GIL while waiting on the lock.

Lib/test/test_asyncio/test_tasks.py

@@ -2924,6 +2924,16 @@ async def coro():
         with self.assertRaises(AttributeError):
             del task._log_destroy_pending
 
+    def test_get_context_uninitialized_segfault(self):
+        # https://github.com/python/cpython/issues/154871
+
+        class UninitializedTask(self.Task):
+            def __init__(self, *args, **kwargs):
+                pass
+
+        task = UninitializedTask()
+        self.assertIsNone(task.get_context())
+
 
 @unittest.skipUnless(hasattr(futures, '_CFuture') and
                      hasattr(tasks, '_CTask'),

Lib/test/test_free_threading/test_collections.py

@@ -1,5 +1,5 @@
 import unittest
-from collections import deque
+from collections import OrderedDict, deque
 from copy import copy
 from test.support import threading_helper
 
@@ -49,5 +49,30 @@ def mutate():
         )
 
 
+class TestOrderedDict(unittest.TestCase):
+    def test_iterator_update_clear_race(self):
+        # gh-151627: OrderedDict iterator construction must not race with
+        # concurrent clear()/update() operations that mutate the linked list.
+        od = OrderedDict((i, i) for i in range(100))
+
+        def mutate():
+            for i in range(5000):
+                od.clear()
+                od.update(((i, i), (i + 1, i + 1), (i + 2, i + 2)))
+
+        def iterate():
+            for _ in range(5000):
+                try:
+                    for _ in od:
+                        pass
+                    list(reversed(od))
+                except RuntimeError:
+                    pass
+
+        threading_helper.run_concurrently(
+            [mutate, *[iterate for _ in range(8)]],
+        )
+
+
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Library/2026-06-19-08-30-00.gh-issue-151627.xY7kLm.rst

@@ -0,0 +1,2 @@
+Fix a crash in :class:`collections.OrderedDict` iterators in free-threaded
+builds when the dictionary is concurrently cleared or updated.

Misc/NEWS.d/next/Library/2026-07-29-19-48-59.gh-issue-154871.tgZILS.rst

@@ -0,0 +1,2 @@
+Fixed a crash in :meth:`asyncio.Task.get_context`
+when called on an uninitialized task.

Modules/_asynciomodule.c

@@ -2786,7 +2786,11 @@ static PyObject *
 _asyncio_Task_get_context_impl(TaskObj *self)
 /*[clinic end generated code: output=6996f53d3dc01aef input=87c0b209b8fceeeb]*/
 {
-    return Py_NewRef(self->task_context);
+    if (self->task_context) {
+        return Py_NewRef(self->task_context);
+    }
+
+    Py_RETURN_NONE;
 }
 
 /*[clinic input]

Objects/odictobject.c

@@ -1958,11 +1958,13 @@ odictiter_new(PyODictObject *od, int kind)
     }
 
     di->kind = kind;
+    Py_BEGIN_CRITICAL_SECTION(od);
     node = reversed ? _odict_LAST(od) : _odict_FIRST(od);
     di->di_current = node ? Py_NewRef(_odictnode_KEY(node)) : NULL;
     di->di_size = PyODict_SIZE(od);
     di->di_state = od->od_state;
     di->di_odict = (PyODictObject*)Py_NewRef(od);
+    Py_END_CRITICAL_SECTION();
 
     _PyObject_GC_TRACK(di);
     return (PyObject *)di;

Objects/unicodeobject.c

@@ -14726,6 +14726,15 @@ intern_common(PyInterpreterState *interp, PyObject *s /* stolen */,
     }
 #endif
 
+    // Why _Py_LOCK_DONT_DETACH is used here: waiting for the interned mutex
+    // must not detach the thread state. Extension code is expected to
+    // detach before blocking on opaque external synchronization. However,
+    // the lock used for C++ static initialization is hidden, making
+    // that difficult, and it is common for C++ extensions to call
+    // PyUnicode_InternFromString() from static initializers. Detaching here
+    // can therefore deadlock: a stop-the-world pause may prevent the lock
+    // owner from reattaching while the pause waits for another attached
+    // thread blocked on the hidden lock.
     FT_MUTEX_LOCK_FLAGS(INTERN_MUTEX, _Py_LOCK_DONT_DETACH);
     PyObject *t;
     {