add atomic global counter system

CHANGES/1328.bugfix.rst

@@ -0,0 +1,2 @@
+Fixed global counter system using an atomic variable.
+-- by :user:`Vizonex`.

multidict/_multilib/state.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <stdatomic.h>
+
 /* State of the _multidict module */
 typedef struct {
     PyTypeObject *IStrType;
@@ -26,7 +28,7 @@ typedef struct {
     PyObject *str_lower;
     PyObject *str_name;
 
-    uint64_t global_version;
+    _Atomic uint64_t global_version;
 } mod_state;
 
 static inline mod_state *
@@ -128,7 +130,9 @@ get_mod_state_by_def(PyObject *self)
 static inline uint64_t
 NEXT_VERSION(mod_state *state)
 {
-    return ++state->global_version;
+    return atomic_fetch_add_explicit(
+               &state->global_version, 1, memory_order_relaxed) +
+           1;
 }
 
 #ifdef __cplusplus

setup.py

@@ -24,6 +24,13 @@
             "-Werror",
         ]
     )
+else:
+    CFLAGS.extend(
+        [
+            "/std:c11",
+            "/experimental:c11atomics",
+        ]
+    )
 
 extensions = [
     Extension(

tests/isolated/multidict_global_counter.py

@@ -0,0 +1,32 @@
+import threading
+import multidict
+from multidict import MultiDict
+import sysconfig
+
+FREETHREADED = bool(sysconfig.get_config_var("Py_GIL_DISABLED"))
+
+
+md: MultiDict[int] = MultiDict()
+N, M = 3, 100
+baseline = multidict.getversion(md)  # type: ignore[arg-type]
+
+
+def worker(tid: int) -> None:
+    for i in range(M):
+        md[f"k{tid}_{i}"] = i
+
+
+if (__name__ == "__main__") and FREETHREADED:
+    threads = [threading.Thread(target=worker, args=(tid,)) for tid in range(N)]
+    for t in threads:
+        t.start()
+    for t in threads:
+        t.join()
+
+    observed = multidict.getversion(md) - baseline  # type: ignore[arg-type]
+    expected = N * M
+    assert expected == observed, (
+        f"expected delta: {expected}"
+        f"   observed: {observed}   "
+        f"lost: {expected - observed}"
+    )

tests/test_leaks.py

@@ -18,6 +18,7 @@
         "multidict_type_leak.py",
         "multidict_type_leak_items_values.py",
         "multidict_pop.py",
+        "multidict_global_counter.py",
     ),
 )
 @pytest.mark.leaks