撰写Linux is actually always a problem= =, but I really love to solve them ^_^
Recently I finally worked out why my logout from plasma desktop to GDM, my system will halt, and why I can never enable vertical synchronization for my kwin. — The reason is, Wayland.
GDM has been using Wayland as its default display server since a certain version. Unfortunately, it doesn’t seem work well with my laptop. So now I disabled it. And everything works pretty fine now.