gh-121621: Use PyMutex for writes to asyncio state

Modules/_asynciomodule.c

@@ -81,6 +81,7 @@ typedef struct futureiterobject futureiterobject;
 
 /* State of the _asyncio module */
 typedef struct {
+    PyMutex mutex;
     PyTypeObject *FutureIterType;
     PyTypeObject *TaskStepMethWrapper_Type;
     PyTypeObject *FutureType;
@@ -341,8 +342,10 @@ get_running_loop(asyncio_state *state, PyObject **loop)
             }
         }
 
+        PyMutex_Lock(&state->mutex);
         state->cached_running_loop = rl;
         state->cached_running_loop_tsid = ts_id;
+        PyMutex_Unlock(&state->mutex);
     }
 
 
@@ -384,8 +387,10 @@ set_running_loop(asyncio_state *state, PyObject *loop)
         return -1;
     }
 
+    PyMutex_Lock(&state->mutex);
     state->cached_running_loop = loop; // borrowed, kept alive by ts_dict
     state->cached_running_loop_tsid = PyThreadState_GetID(tstate);
+    PyMutex_Unlock(&state->mutex);
 
     return 0;
 }
@@ -1668,9 +1673,11 @@ FutureIter_dealloc(futureiterobject *it)
     }
 
     if (state && state->fi_freelist_len < FI_FREELIST_MAXLEN) {
+        PyMutex_Lock(&state->mutex);
         state->fi_freelist_len++;
         it->future = (FutureObj*) state->fi_freelist;
         state->fi_freelist = it;
+        PyMutex_Unlock(&state->mutex);
     }
     else {
         PyObject_GC_Del(it);
@@ -1877,9 +1884,11 @@ future_new_iter(PyObject *fut)
     ENSURE_FUTURE_ALIVE(state, fut)
 
     if (state->fi_freelist_len) {
+        PyMutex_Lock(&state->mutex);
         state->fi_freelist_len--;
         it = state->fi_freelist;
         state->fi_freelist = (futureiterobject*) it->future;
+        PyMutex_Unlock(&state->mutex);
         it->future = NULL;
         _Py_NewReference((PyObject*) it);
     }
@@ -2028,8 +2037,10 @@ register_task(asyncio_state *state, TaskObj *task)
     assert(state->asyncio_tasks.head != NULL);
 
     task->next = state->asyncio_tasks.head;
+    PyMutex_Lock(&state->mutex);
     state->asyncio_tasks.head->prev = task;
     state->asyncio_tasks.head = task;
+    PyMutex_Unlock(&state->mutex);
 }
 
 static int
@@ -2052,7 +2063,9 @@ unregister_task(asyncio_state *state, TaskObj *task)
     task->next->prev = task->prev;
     if (task->prev == NULL) {
         assert(state->asyncio_tasks.head == task);
+        PyMutex_Lock(&state->mutex);
         state->asyncio_tasks.head = task->next;
+        PyMutex_Unlock(&state->mutex);
     } else {
         task->prev->next = task->next;
     }
@@ -2213,7 +2226,9 @@ _asyncio_Task___init___impl(TaskObj *self, PyObject *coro, PyObject *loop,
         // optimization: defer task name formatting
         // store the task counter as PyLong in the name
         // for deferred formatting in get_name
+        PyMutex_Lock(&state->mutex);
         name = PyLong_FromUnsignedLongLong(++state->task_name_counter);
+        PyMutex_Unlock(&state->mutex);
     } else if (!PyUnicode_CheckExact(name)) {
         name = PyObject_Str(name);
     } else {
@@ -3750,6 +3765,7 @@ module_free_freelists(asyncio_state *state)
     PyObject *current;
 
     next = (PyObject*) state->fi_freelist;
+    PyMutex_Lock(&state->mutex);
     while (next != NULL) {
         assert(state->fi_freelist_len > 0);
         state->fi_freelist_len--;
@@ -3760,6 +3776,7 @@ module_free_freelists(asyncio_state *state)
     }
     assert(state->fi_freelist_len == 0);
     state->fi_freelist = NULL;
+    PyMutex_Unlock(&state->mutex);
 }
 
 static int
@@ -3844,6 +3861,7 @@ module_init(asyncio_state *state)
 {
     PyObject *module = NULL;
 
+    PyMutex_Lock(&state->mutex);
     state->asyncio_mod = PyImport_ImportModule("asyncio");
     if (state->asyncio_mod == NULL) {
         goto fail;
@@ -3913,10 +3931,13 @@ module_init(asyncio_state *state)
         goto fail;
     }
 
+    PyMutex_Unlock(&state->mutex);
+
     Py_DECREF(module);
     return 0;
 
 fail:
+    PyMutex_Unlock(&state->mutex);
     Py_CLEAR(module);
     return -1;
 
@@ -3947,9 +3968,12 @@ static int
 module_exec(PyObject *mod)
 {
     asyncio_state *state = get_asyncio_state(mod);
+
+    PyMutex_Lock(&state->mutex);
     Py_SET_TYPE(&state->asyncio_tasks.tail, state->TaskType);
     _Py_SetImmortalUntracked((PyObject *)&state->asyncio_tasks.tail);
     state->asyncio_tasks.head = &state->asyncio_tasks.tail;
+    PyMutex_Unlock(&state->mutex);
 
 #define CREATE_TYPE(m, tp, spec, base)                                  \
     do {                                                                \