gh-118297: Make Sure All Pending Calls Run in _Py_FinishPendingCalls() (gh-118298)

Author: ericsnowcurrently

Python/ceval_gil.c

@@ -991,12 +991,34 @@ _Py_FinishPendingCalls(PyThreadState *tstate)
     assert(PyGILState_Check());
     assert(_PyThreadState_CheckConsistency(tstate));
 
-    if (make_pending_calls(tstate) < 0) {
-        PyObject *exc = _PyErr_GetRaisedException(tstate);
-        PyErr_BadInternalCall();
-        _PyErr_ChainExceptions1(exc);
-        _PyErr_Print(tstate);
-    }
+    struct _pending_calls *pending = &tstate->interp->ceval.pending;
+    struct _pending_calls *pending_main =
+            _Py_IsMainThread() && _Py_IsMainInterpreter(tstate->interp)
+            ? &_PyRuntime.ceval.pending_mainthread
+            : NULL;
+    /* make_pending_calls() may return early without making all pending
+       calls, so we keep trying until we're actually done. */
+    int32_t npending;
+#ifndef NDEBUG
+    int32_t npending_prev = INT32_MAX;
+#endif
+    do {
+        if (make_pending_calls(tstate) < 0) {
+            PyObject *exc = _PyErr_GetRaisedException(tstate);
+            PyErr_BadInternalCall();
+            _PyErr_ChainExceptions1(exc);
+            _PyErr_Print(tstate);
+        }
+
+        npending = _Py_atomic_load_int32_relaxed(&pending->npending);
+        if (pending_main != NULL) {
+            npending += _Py_atomic_load_int32_relaxed(&pending_main->npending);
+        }
+#ifndef NDEBUG
+        assert(npending_prev > npending);
+        npending_prev = npending;
+#endif
+    } while (npending > 0);
 }
 
 int