Comment # 7 on bug 93784 from Nicolas Koch

I could fix this problem by enabling DRI3 for the intel driver like this:

cat /etc/X11/xorg.conf.d/020-intel.conf

Section "Device"
   Identifier  "Intel Graphics"
   Driver      "intel"
   Option      "TearFree" "true"
   Option      "DRI" "3"
EndSection

No more GPU hangups and other funny stuff happening, at least glxgears works
now (no more black screen).

It would be nice, if someone found out why this is behaving strange when only
DRI2 is enabled, though.