Created attachment 196786 [details]
gdb session

After I step away from the machine for a while, when I come back and wake up from screensaver, gnome-shell is unresponsive with the following symptoms:

1) message tray doesn't go away
2) clicking any of the top panel icons highlights them, but the bubbles don't show up
3) super key / activities view / alt+f2 for run dialog don't do anything
4) window focus switching works briefly, but then focus is stuck on a single window

kill -9-ing the shell appears to be the only way to kill it once it gets in this state, as well.

attached is a gdb session from during a "freeze" (not a full lockup, so not sure if it's actually helpful?)