Hello!

Launching War Thunder make GPU stuck, and then system is hard lockup. This
issue is starting to happen after upgrade from Mesa 17.2.2 with libdrm 2.4.83
to 17.3.0rc4 with libdrm 2.4.85 (from Padoka Stable PPA
https://launchpad.net/~paulo-miguel-dias/+archive/ubuntu/pkppa ) on Kubuntu
17.10 x86_64. As soon as I rollback to Mesa 17.2.2 and libdrm 2.4.83, GPU
lockup is no longer reproducible, but then there is another issue: bug 100387

Issue is reproducible on both of iGPU and dGPU. Please look into attached log.

Hardware: 
Acer Aspire 7560G, AMD A8-3500M
AMD Radeon HD 6620G iGPU, AMD Radeon HD 6650M dGPU.

Software:
Kubuntu 17.10 x86_64, Linux 4.14.1.
radeon DDX and modesetting DDX was tested, no difference.