My take on the backtrace is that the set_screen_power_mode request hangs somewhere in Mir, and since it holds the lock, it blocks both dimmer_alarm_notification and keep_display_on_temporarily (which is a result of user input). If my assumption is correct, we need to find why and where in Mir we block, so it would be great if we had debug symbols for mir (and libstdc++ and libc) for the USC backtrace.
My take on the backtrace is that the set_screen_ power_mode request hangs somewhere in Mir, and since it holds the lock, it blocks both dimmer_ alarm_notificat ion and keep_display_ on_temporarily (which is a result of user input). If my assumption is correct, we need to find why and where in Mir we block, so it would be great if we had debug symbols for mir (and libstdc++ and libc) for the USC backtrace.