https://bugs.freedesktop.org/show_bug.cgi?id=93341
--- Comment #3 from Andreas Kilgus kilgus@fuenfsieben.de --- Happens at low system/graphical load, maybe related to chromium (IIRC, the last two times it occured I was actively using chromium).
Radeon R7 260X
Mesa 11.1.2 xorg-x11-server 7.6 1.18.1 kernel 4.4.1