Sometimes syspolicyd completely freezes my Mac

[wojciech-kulik]

Hi,

I experience a complete freeze on my macOS from time to time. It started happening when I installed nix-darwin, a couple of months ago.

I managed to pin down the issue (because sometimes I've got still time before the complete freeze) and it turns out that most likely syspolicyd process is causing that. It starts using a lot of CPU, I manged to show details and I see that it opens /nix/store/.links. When everything is normal, this file is not on the list.

Any idea what could be causing that? And more important how to fix it?
As it happens from time to time, maybe it's related to garbage collecting/hard links optimization?

I have to hard reset my computer every time it happens (by holding the power button).

My config:
MacBook Pro M1 Pro, 2021, 16GB RAM
macOS Sequoia 15.3 (I experienced it on previous versions as well).

[Enzime]

Are you using any kernel extensions?

[wojciech-kulik]

I don't even know what kernel extensions are :D But I'm not using anything crazy.
Just regular apps + nix, I didn't make any changes to macOS SIP or anything like that.

[Enzime]

Do you have nix.settings.auto-optimise-store or nix.optimise.automatic enabled?

[wojciech-kulik]

Yes, here is my config:

 nix.gc = {
    automatic = true;
    interval = [
      {
        Hour = 10;
        Minute = 0;
        Weekday = 1;
      }
    ];
    options = "--delete-older-than 6d";
  };

  nix.optimise = {
    automatic = true;
    interval = [
      {
        Hour = 10;
        Minute = 0;
        Weekday = 2;
      }
    ];
  };

Thank you for helping with that!

[wojciech-kulik]

So it seems like it matches nix.optiimise. The screenshot was taken on Tuesday at 10:43.

[wojciech-kulik]

I found an old screenshot with the same problem that occurred on Nov 4, 2024 (Monday) at 10:21 and based on my config on Monday gc is scheduled and I also remember that sometimes it happened two days in a row, so I guess gc might be causing the same issue. I'm not sure about the internals, but maybe optimise is a part of gc steps?