From reading the backtrace in comment 3, I'm guessing that Thread3 is the Qt GUI thread, which is blocked on a WaitCondition.
Thread 15 is a Mir thread, is blocked on SessionAuthorizer::requestAuthorizationForSession which is waiting for the Qt GUI thread to reply to it.
But as GUI thread blocked, then it blocks Mir at that place.
But why Qt GUI thread blocked is open question. More detailed backtrace would help - I'd start installing qtdeclarative5-dbg and qtbase5-dbg. The dbus DENIED messages are interesting too
From reading the backtrace in comment 3, I'm guessing that Thread3 is the Qt GUI thread, which is blocked on a WaitCondition. er::requestAuth orizationForSes sion which is waiting for the Qt GUI thread to reply to it.
Thread 15 is a Mir thread, is blocked on SessionAuthoriz
But as GUI thread blocked, then it blocks Mir at that place.
But why Qt GUI thread blocked is open question. More detailed backtrace would help - I'd start installing qtdeclarative5-dbg and qtbase5-dbg. The dbus DENIED messages are interesting too