From 28360fa3ac51916d3229de706e0e609a9bad45f6 Mon Sep 17 00:00:00 2001
From: Kumar Aditya <kumaraditya@python.org>
Date: Wed, 8 Oct 2025 19:49:54 +0530
Subject: [PATCH] gh-139774: use relaxed atomics for datetime hashes
 (GH-139775) (cherry picked from commit
 49fb46f555881c9f2d20ca87c8187c8718217c77)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>
---
 Modules/_datetimemodule.c | 47 ++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index ddb9e9fd2e57c0..cb6e3c80224846 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -15,6 +15,7 @@
 #include "pycore_time.h"          // _PyTime_ObjectToTime_t()
 #include "pycore_unicodeobject.h" // _PyUnicode_Copy()
 #include "pycore_initconfig.h"    // _PyStatus_OK()
+#include "pycore_pyatomic_ft_wrappers.h"
 
 #include "datetime.h"
 
@@ -2533,14 +2534,16 @@ static Py_hash_t
 delta_hash(PyObject *op)
 {
     PyDateTime_Delta *self = PyDelta_CAST(op);
-    if (self->hashcode == -1) {
+    Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(self->hashcode);
+    if (hash == -1) {
         PyObject *temp = delta_getstate(self);
         if (temp != NULL) {
-            self->hashcode = PyObject_Hash(temp);
+            hash = PyObject_Hash(temp);
+            FT_ATOMIC_STORE_SSIZE_RELAXED(self->hashcode, hash);
             Py_DECREF(temp);
         }
     }
-    return self->hashcode;
+    return hash;
 }
 
 static PyObject *
@@ -3860,12 +3863,14 @@ static Py_hash_t
 date_hash(PyObject *op)
 {
     PyDateTime_Date *self = PyDate_CAST(op);
-    if (self->hashcode == -1) {
-        self->hashcode = generic_hash(
+    Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(self->hashcode);
+    if (hash == -1) {
+        hash = generic_hash(
             (unsigned char *)self->data, _PyDateTime_DATE_DATASIZE);
+        FT_ATOMIC_STORE_SSIZE_RELAXED(self->hashcode, hash);
     }
 
-    return self->hashcode;
+    return hash;
 }
 
 static PyObject *
@@ -4944,7 +4949,8 @@ static Py_hash_t
 time_hash(PyObject *op)
 {
     PyDateTime_Time *self = PyTime_CAST(op);
-    if (self->hashcode == -1) {
+    Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(self->hashcode);
+    if (hash == -1) {
         PyObject *offset, *self0;
         if (TIME_GET_FOLD(self)) {
             self0 = new_time_ex2(TIME_GET_HOUR(self),
@@ -4966,10 +4972,11 @@ time_hash(PyObject *op)
             return -1;
 
         /* Reduce this to a hash of another object. */
-        if (offset == Py_None)
-            self->hashcode = generic_hash(
+        if (offset == Py_None) {
+            hash = generic_hash(
                 (unsigned char *)self->data, _PyDateTime_TIME_DATASIZE);
-        else {
+            FT_ATOMIC_STORE_SSIZE_RELAXED(self->hashcode, hash);
+        } else {
             PyObject *temp1, *temp2;
             int seconds, microseconds;
             assert(HASTZINFO(self));
@@ -4988,12 +4995,13 @@ time_hash(PyObject *op)
                 Py_DECREF(offset);
                 return -1;
             }
-            self->hashcode = PyObject_Hash(temp2);
+            hash = PyObject_Hash(temp2);
+            FT_ATOMIC_STORE_SSIZE_RELAXED(self->hashcode, hash);
             Py_DECREF(temp2);
         }
         Py_DECREF(offset);
     }
-    return self->hashcode;
+    return hash;
 }
 
 /*[clinic input]
@@ -6451,7 +6459,8 @@ static Py_hash_t
 datetime_hash(PyObject *op)
 {
     PyDateTime_DateTime *self = PyDateTime_CAST(op);
-    if (self->hashcode == -1) {
+    Py_hash_t hash = FT_ATOMIC_LOAD_SSIZE_RELAXED(self->hashcode);
+    if (hash == -1) {
         PyObject *offset, *self0;
         if (DATE_GET_FOLD(self)) {
             self0 = new_datetime_ex2(GET_YEAR(self),
@@ -6476,10 +6485,11 @@ datetime_hash(PyObject *op)
             return -1;
 
         /* Reduce this to a hash of another object. */
-        if (offset == Py_None)
-            self->hashcode = generic_hash(
+        if (offset == Py_None) {
+            hash = generic_hash(
                 (unsigned char *)self->data, _PyDateTime_DATETIME_DATASIZE);
-        else {
+            FT_ATOMIC_STORE_SSIZE_RELAXED(self->hashcode, hash);
+        } else {
             PyObject *temp1, *temp2;
             int days, seconds;
 
@@ -6503,12 +6513,13 @@ datetime_hash(PyObject *op)
                 Py_DECREF(offset);
                 return -1;
             }
-            self->hashcode = PyObject_Hash(temp2);
+            hash = PyObject_Hash(temp2);
+            FT_ATOMIC_STORE_SSIZE_RELAXED(self->hashcode, hash);
             Py_DECREF(temp2);
         }
         Py_DECREF(offset);
     }
-    return self->hashcode;
+    return hash;
 }
 
 /*[clinic input]