After installing nixos I had some issues with the linux kernel and possibly kde. At boot I would get errors like this.
https://www.dropbox.com/s/bj50sqgfgy9yp1b/2017-06-20%2020.43.20.jpg?dl=0 https://www.dropbox.com/s/16mj6taamdekqyw/2017-06-21%2021.08.43.jpg?dl=0 https://www.dropbox.com/s/o29rerznr38dkw0/2017-06-21%2021.06.05.jpg?dl=0
And once in Konsole I got this error just before the system froze.
After various searches for smp.c line 127 it seems like a bug in linux. I found this issue for arch linux which indicates it was fixed for linux 4.9.6.
After asking about the issue on reddit it was suggested to add this to my configuration.nix
boot.kernelPackages = pkgs.linuxPackages_latest
After adding this and performing a full update it appears to have solved my problem.
As a note this command will get the previous log for X
journalctl -u display-manager --boot=-1