It's only an issue when you have a C callback that calls a Python code, because you have C code in the middle of your stack thus you can not move the stack fram

It's only an issue when you have a C callback that calls a Python code, because you have C code in the middle of your stack thus you can not move the stack frames back and forth (because the C code can reference stack addresses). I may be wrong but most of the C calls in Python do not have callbacks and you can pin the coroutine to the kernel thread if there is a callback.