You can have more than one thread state for a thread if they

correspond to different interpreters (I hope, please revert if this is
wrong :).

diff --git a/Python/pystate.c b/Python/pystate.c
index abca8ddfdff1444f3ee9528084ee05c9e28ca302..e2cf7c564d5125ce731b4e9cd2352da8cf8c0d3c 100644 (file)
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -289,7 +289,7 @@ PyThreadState_Swap(PyThreadState *new)
 #if defined(Py_DEBUG) && defined(WITH_THREAD)
        if (new) {
                PyThreadState *check = PyGILState_GetThisThreadState();
-               if (check && check != new)
+               if (check && check->interp == new->interp && check != new)
                        Py_FatalError("Invalid thread state for this thread");
        }
 #endif