From time to time, often after I've restored from sleep or finished playing a Steam game, one of my CPU cores is pinned at 100% with no indication of what might be doing it. Running htop, btop, or GNOME system monitor all show the same thing: CPU0 at 100% while the rest are doing near-nothing, and no process in particular seems to be using those resources.
If I restart, it's back to normal, and sometimes I can play a game in Steam or let the computer go to sleep and it doesn't do this, but it happens often enough that's annoying/confusing so I'd like to know if there's a way to either (a) diagnose which processes are using which CPU cores, or (b) somehow "reset" the checking of these values to make sure that something's not just being misreported.
This is a desktop system running Arch & GNOME.
I've had this happen with AI stuff that runs in a Python venv. It only happens with apps that use multi threading, and usually when something is interrupted in an unintended or unaccounted for way. I usually see it when I start screwing with code stuff, but also from changing the softmax settings during generation or crashing other stuff while hacking around. There may be a bug of some kind, but I think it likely has more to do with killing the root threading process and leaving an abandoned child that doesn't get handled by the kernel process scheduler in the standard way. If this happens I restart too.