Happens on X11 only with active compositing. This seems to be a freeze in MESA, but I create this bug to track the upstream solution or possible solutions from our side. Upstream bug report: https://bugs.freedesktop.org/show_bug.cgi?id=103234 I use Mesa 17.2.4. I have yet to test if this happens with Mesa Master as well, as was proposed in the upstream bug report by Nicolai.
*** This bug has been marked as a duplicate of bug 385626 ***