Note: this is not a dupe of this, as my computer has an AMD graphics chip, and not an Nvidia graphics chip
This appeared after I have turned off my laptop by pressing and holding a power button. Before that, I have done a few system updates, that there waiting for reboot (I keep laptop ON or on stand-by all the time).
Ubuntu 16.04 64-bit. AMD A6-7310 APU, 12 GB DDR3. Gallium 0.4 on AMD MULLINS (DRM 2.43.0 / 4.4.0-72-generic, LLVM 4.0.0)
After installing Kernel 4.8 (hardware enablement stack), the issue disappeared.