Comment 34 for bug 1174495

I've bisected the issue to this commit:

35840ab189595b817fa8b1a1df8cc92474a7c38d st/dri: implement MSAA for GLX/DRI2 framebuffers

The only thing that was recompiled was mesa, with the following options:

    --with-dri-driverdir=/usr/lib/xorg/modules/dri
    --with-gallium-drivers=r600,swrast
    --with-dri-drivers=
    --with-egl-platforms=drm,x11
    --enable-gallium-egl --enable-shared-glapi
    --enable-gallium-llvm
    --enable-glx-tls
    --enable-gles1
    --enable-gles2
    --enable-egl
    --enable-dri
    --enable-glx
    --enable-xa
    --enable-osmesa
    --enable-gbm
    --enable-texture-float

The issue was triggered by restarting kwin (kwin --replace) between each compile and locking and unlocking the screen.