Ban or tighten moving event loop across threads

[fantix]

Since compio-rs/compio#660 (#5), Proactor is no longer Send (which is more strict and correct). Moving an event loop across threads should now be either banned - which violates 100% Python compatibility (in a good way), or requires very careful and clean boundaries.

[winstxnhdw]

If this is banned, does this mean all synchronous web frameworks like Flask and Django will not be able to use compio because loop.run_coroutine_threadsafe, is no longer possible?

[fantix]

ohh loop.run_coroutine_threadsafe has to be supported. the python loop object may still be referenced from threads, it's just that the same loop cannot be stopped, moved to another thread and start again there.