> Regarding C extensions, I think clear documentation that extension authors need to check for signals in any code that might run for a few hundred microseconds or longer is the best approach.

Python 3.10 doesn't require it. If you want to change Python 3.11 behavior, please announce the change on python-dev and capi-sig mailing lists, and document it carefully in What's New in Python 3.11.

I'm not talking about checking frequently interruptions while a function is running, I'm only talking about the "end" of a C function (exit). In Python 3.10, ceval.c does it automatically.

        case TARGET(CALL_FUNCTION): {
            PREDICTED(CALL_FUNCTION);
            PyObject **sp, *res;
            sp = stack_pointer;
            res = call_function(tstate, &trace_info, &sp, oparg, NULL);
            stack_pointer = sp;
            PUSH(res);
            if (res == NULL) {
                goto error;
            }
            CHECK_EVAL_BREAKER();  // <==== HERE
            DISPATCH();
        }