I have Qt configured (in QtUbuntu/QtMir) to use multi-threaded GL rendering, so we're probably hitting Nouveau's limitations here.
As workaround, I can add code to QtUbuntu/QtMir use single-threaded GL for Nouveau.
If this is easily reproduced, can you try
initctl set-env --global QSG_RENDER_LOOP=basic
and see if everything is more stable? If so, the workaround should do the trick
I have Qt configured (in QtUbuntu/QtMir) to use multi-threaded GL rendering, so we're probably hitting Nouveau's limitations here.
As workaround, I can add code to QtUbuntu/QtMir use single-threaded GL for Nouveau.
If this is easily reproduced, can you try
initctl set-env --global QSG_RENDER_ LOOP=basic
and see if everything is more stable? If so, the workaround should do the trick