Anki 24.04 does not close properly

[dae]

I recently updated to latest anki version 24.04 on my Fedora 39 (Linux).
In this version when I start anki and close it multiple times without any changes made to the decks or settings.
At one point it closes with an instant effect and then If I start to run it again I cannot do it because it says Already running in terminal window. For which I have to go to system monitor and Kill it from there to start it again.
It was not happening in earlier version 23.12.
I just want it to close properly so I do not have to go in system monitor to kill the process.

Originally reported on https://forums.ankiweb.net/t/anki-24-04-does-not-close-properly/43185/15

Probably connected to 7784321. Maybe we could swallow errors when accessing the timers, or have some 'shutting down' flag that causes the errors to be ignored?

[dae]

For me, changing 0.5 to 0.3 in the following line caused it to happen the first time I tried to reproduce it:

    time_to_wait = 0.3 - elapsed_time

Edit: but it doesn't happen when I try again. Might have just gotten lucky? I got a similar traceback to the one reported in the thread above, in any case.

[voczi]

Race condition, maybe?

I was personally just able to reproduce the bug once. For now I'm going to use a mutex for the entire do_window_cleanup code. I'll see if it helps.

[voczi]

Just figured out that you can study a card to consistently reproduce the bug.
Weird because the OP of that thread said that the bug never happens when they have a sync-able change. I'm on Windows 11, and the OP did mention something about different behavior between Windows and Fedora.