Comment 22 for bug 1290416

From what I can tell, unity8 is in a deadlock because the mutex that protects Qt's event system was locked by Qt itself in some thread at some point in time and never released. Then when other threads wake up because, eg, a mir session is being closed and its wants to inform objects in the Qt side about it (such as some qml items) by posting some event or emitting a signal Qt internally tries to acquire that event system lock before doing so and then get blocked indefinitely.

Besides this basic assessment I'm pretty much clueless at the moment :)

Also wans't able to reproduce the freeze yet (got a unity8 crash+restart though)