Created attachment 113261 [details]
dmesg during lockup

My system completely freezes while playing XCOM and I have to use SysRQ to
reboot. Waiting does not help.

Radeon R9 270, Fedora 21, kernel-3.18.6-200.fc21.x86_64,
mesa-dri-drivers-10.4.3-1.20150124.fc21.x86_64,
xorg-x11-drv-ati-7.5.0-1.fc21.x86_64, llvm-libs-3.5.0-6.fc21.x86_64.