From: Victor Stinner <vstinner@python.org>
Date: Sat, 23 May 2026 06:57:27 +0000 (+0200)
Subject: [3.15] Revert "[3.15] gh-146452: Improve locking granularity in pickle's batch_dict_e... 
X-Git-Tag: v3.15.0b2~91
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=795dd3bd3500c49c6a08281a15a9472a28f416d3;p=thirdparty%2FPython%2Fcpython.git

[3.15] Revert "[3.15] gh-146452: Improve locking granularity in pickle's batch_dict_exact and fix race condition (GH-150025) (#150039)" (#150262)

Revert "[3.15] gh-146452: Improve locking granularity in pickle's batch_dict_exact and fix race condition (GH-150025) (#150039)"

This reverts commit 66ade2861fec1d6c18998710938a1c71fde5f76b.
---

diff --git a/Misc/NEWS.d/next/Library/2026-05-18-15-30-34.gh-issue-146452.RM0EVJ.rst b/Misc/NEWS.d/next/Library/2026-05-18-15-30-34.gh-issue-146452.RM0EVJ.rst
deleted file mode 100644
index 66f9acf6c710..000000000000
--- a/Misc/NEWS.d/next/Library/2026-05-18-15-30-34.gh-issue-146452.RM0EVJ.rst
+++ /dev/null
@@ -1,2 +0,0 @@
-Fix race condition when pickling dictionaries in free threaded builds. Also
-reduce critical section cover.
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index 15d95c658d6f..9874f9475ac0 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -3450,9 +3450,6 @@ batch_dict(PickleState *state, PicklerObject *self, PyObject *iter, PyObject *or
  * Returns 0 on success, -1 on error.
  *
  * Note that this currently doesn't work for protocol 0.
-
- * gh-146452: Wrap the dict iteration in a critical sections to prevent
- * concurrent mutation from invalidating PyDict_Next() iteration state.
  */
 static int
 batch_dict_exact(PickleState *state, PicklerObject *self, PyObject *obj)
@@ -3469,24 +3466,15 @@ batch_dict_exact(PickleState *state, PicklerObject *self, PyObject *obj)
     assert(self->proto > 0);
 
     dict_size = PyDict_GET_SIZE(obj);
+    assert(dict_size);
 
     /* Write in batches of BATCHSIZE. */
     Py_ssize_t total = 0;
     do {
         if (dict_size - total == 1) {
-            int next;
-            Py_BEGIN_CRITICAL_SECTION(obj);
-            next = PyDict_Next(obj, &ppos, &key, &value);
-            if (next) {
-                Py_INCREF(key);
-                Py_INCREF(value);
-            }
-            Py_END_CRITICAL_SECTION();
-            if (!next) {
-                PyErr_SetString(PyExc_RuntimeError,
-                                "dictionary changed size during iteration");
-                goto error;
-            }
+            PyDict_Next(obj, &ppos, &key, &value);
+            Py_INCREF(key);
+            Py_INCREF(value);
             if (save(state, self, key, 0) < 0) {
                 goto error;
             }
@@ -3504,18 +3492,9 @@ batch_dict_exact(PickleState *state, PicklerObject *self, PyObject *obj)
         i = 0;
         if (_Pickler_Write(self, &mark_op, 1) < 0)
             return -1;
-        int next;
-        while (1) {
-            Py_BEGIN_CRITICAL_SECTION(obj);
-            next = PyDict_Next(obj, &ppos, &key, &value);
-            if (next) {
-                Py_INCREF(key);
-                Py_INCREF(value);
-            }
-            Py_END_CRITICAL_SECTION();
-            if (!next) {
-                break;
-            }
+        while (PyDict_Next(obj, &ppos, &key, &value)) {
+            Py_INCREF(key);
+            Py_INCREF(value);
             if (save(state, self, key, 0) < 0) {
                 goto error;
             }