Comment 11 for bug 1584784

I didn't include an Xmir stack trace yesterday because it didn't appear stuck, it was submitting buffers (black frames) repeatedly.

I compiled Xmir and added some logs. I caught swap_buffers blocking up in Xmir (in the pocket desktop scenario only, seems to be a racy, perhaps on how big the frame size is) but it seems the block triggers the scenario.

And from poking around Xmir when the problem occurs, it seems like the "BlockHandler" is only called once, and the system stuck submitting frames repeatedly, instead of servicing the WM+Xapp connection requests.

And furthermore, I think that the system only got in this case with libertine+UAL+unity8+pocketdesktop because when UAL's involved, Xmir+WM+Xapp get launched in very close sucession, whereas with the desktop test plan, they're manually launched, so they start "far" apart.