call_soon_after_close.diff looks good but also incomplete: call_later, call_at and run_in_executor should also raise an exception if the event loop is closed.

You should also add call_soon_threadsafe to the test.

> So for consistency this patch should grow quite a bit (unless create_connection, add_reader etc. already raise in this case).

Yes, add_reader raises an exception and there is an unit test to ensure that.

create_task() is a little bit special, it does not schedule immediatly a coroutine. IMO it makes sense to fail if the loop was closed, I don't see how the task can be executed if the loop was executed, so calling create_task() on a closed loop looks like a bug.

I suggest to modify the following methods:
- call_soon, call_soon_threadsafe
- call_at, call_later
- run_in_executor
- create_task
- add_signal_handler
- subprocess_exec, subprocess_shell

Did I miss something?

I'm not sure that *all* asyncio methods should must call _check_closed(), it may make the code harder to read. If the basic functions like call_soon and add_reader already handle the closed status, I guess that all other methods will fail loudly, so they don't need to be modified.

For example, stop() calls call_soon() and so will also raises an exception if the loop is closed.

Maybe we should add almost all methods to the test checking that calling these methods on a closed loop fail.