https://bugs.freedesktop.org/show_bug.cgi?id=71697
--- Comment #4 from Thue Janus Kristensen thuejk@gmail.com --- It is probably the "GtkDrawingArea - Lines" component. The same problem is described in bug 68524. It is caused by the glamor software fallback being extremely slow. And obviously somehow mostly excluding other drawing operations.
On my system, it doesn't crash the system, it only makes it extremely slow to respond.