Code review comment for lp:~afrantzis/unity-system-compositor/fix-1491566-deadlock

> Do you really need the before_* methods in MirScreen?
> You could simply override the method and call a before function<> inside the test setup.

Ack. Changed!

> Why does that fix the issue? The lock ordering is still the same now?

The LockableCallback::lock() and unlock() functions are called before acquiring the internal alarm lock ([1]). So when the alarm callback occurs we now get [lock MirScreen], [lock Alarm], [dispatch callback] instead of [lock Alarm], [dispatch callback], [lock MirScreen] we had previously.

[1] http://bazaar.launchpad.net/~mir-team/mir/development-branch/view/head:/src/server/glib_main_loop_sources.cpp#L308