Make set cache as atomic operation

python · corona10 · Nov 21, 2024 · Nov 9, 2024 · Nov 9, 2024 · Nov 9, 2024
commit 67983665ded9c9395d6f78a87e7331f7a99c004b
diff --git a/Python/specialize.c b/Python/specialize.c
@@ -689,6 +689,21 @@
 #endif
 }
 
+static inline int
+set_cache_verison(uint16_t *old_version, uint32_t new_version)
+{
+#ifdef Py_GIL_DISABLED
+    uint32_t old_version_val = read_u32(old_version);
+    if (!_Py_atomic_compare_exchange_uint32((uint32_t *)old_version, &old_version_val, new_version)) {
+        return 0;
+    }
+    return 1;
+#else
+    write_u32(cache, new_version);
+    return 1;
+#endif
+}
+
 static inline void
 set_counter(_Py_BackoffCounter *counter, _Py_BackoffCounter value)
 {
@@ -2742,8 +2757,17 @@
             unspecialize(instr, SPEC_FAIL_OUT_OF_VERSIONS);
             return;
         }
+#ifdef Py_GIL_DISABLED
+        if (read_u32(cache->version) > version) {
+            unspecialize(instr, SPEC_FAIL_OUT_OF_VERSIONS);
+            return;
+        }
+#endif
+        if (!set_cache_verison(cache->version, version)) {
+            unspecialize(instr, SPEC_FAIL_OUT_OF_VERSIONS);
+            return;
+        }
         specialize(instr, TO_BOOL_ALWAYS_TRUE);
-        write_u32(cache->version, version);
         assert(version);
         return;
     }