[kccqzy]

Yes sure. Thought experiment: what happens when these parallel kernels suddenly need to call back in to Python? Let's say you have a multithreaded sorting library. If you are sorting numbers then fine nothing changes. But if you are sorting objects you need to use a single thread because you need to call PyObject_RichCompare. These new parallel kernels will then try to call PyObject_RichCompare from multiple threads.