Comment 6 for bug 1623507

It appears this crash is a secondary crash that's come after an earlier one.

We have two compositor threads (two monitors connected). One of them has crashed in the renderer during glClear, which would be a nouveau bug(?).

Then our crash handler has tried to clean up and change VTs back to their original state, which races with the other compositor thread that's still running. And once the active VT changes, that second compositor thread will fail to schedule a page flip, which is expected because Mir no longer has DRM mastership.

So there are two bugs here:
  (1) nouveau crashed in glClear. That's the main problem because it was the trigger for the second.
  (2) Our DRM page flipping code can't deal with flip failures without crashing. But we already know about that thanks to bug 1489689 and bug 1584894.