 modesetting in dri2 mode is fine here :). Probably, but do you use xserver's
modesetting driver in dri3 mode?

 There are whole bunch of piglit crashes and gpu lockups here with anything
dri3 related - be it with xserver's modeseting or radeon ddx (i tried this
patched radeon https://github.com/iXit/xf86-video-ati/commits/master and it
suffer from the same issues like modesetting)