https://github.com/python/cpython/commit/b770b2350e5c034afeee4213c9d63348f6f3b341
commit: b770b2350e5c034afeee4213c9d63348f6f3b341
branch: main
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2026-05-22T22:22:47+02:00
summary:
Revert "gh-146452: Improve locking granularity in pickle's batch_dict_exact and
fix race condition (#150025)" (#150261)
This reverts commit 57a0e570d36f41b953a91bbaf4262a5d05d0391b.
files:
D Misc/NEWS.d/next/Library/2026-05-18-15-30-34.gh-issue-146452.RM0EVJ.rst
M Modules/_pickle.c
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 66f9acf6c710a7..00000000000000
--- 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 253ba7f743ec71..2d82438f0d308d 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -3463,12 +3463,9 @@ 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)
+batch_dict_exact_impl(PickleState *state, PicklerObject *self, PyObject *obj)
{
PyObject *key = NULL, *value = NULL;
int i;
@@ -3482,24 +3479,15 @@ 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;
}
@@ -3517,18 +3505,9 @@ 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;
}
@@ -3559,6 +3538,18 @@ batch_dict_exact(PickleState *state, PicklerObject
*self, PyObject *obj)
return -1;
}
+/* gh-146452: Wrap the dict iteration in a critical section to prevent
+ concurrent mutation from invalidating PyDict_Next() iteration state. */
+static int
+batch_dict_exact(PickleState *state, PicklerObject *self, PyObject *obj)
+{
+ int ret;
+ Py_BEGIN_CRITICAL_SECTION(obj);
+ ret = batch_dict_exact_impl(state, self, obj);
+ Py_END_CRITICAL_SECTION();
+ return ret;
+}
+
static int
save_dict(PickleState *state, PicklerObject *self, PyObject *obj)
{
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