Comment 5 for bug 1008808

I could reproduce this again today.

The display was synced, but completely black with the mouse cursor also not visible. I tried a few things, such as switching consoles and replugging the hdmi cable. No effect.

Then I logged in from the text console and noticed compiz eating up 100% cpu. After ptracing compiz with strace and then gdb, the process somehow broke out of its busy loop and quietly returned to the main event loop. When I switched back to the X display, everything was back to normal and I could unlock the gnome screensaver.

Here's my hypothesis based on the above observations: compiz and the X server keep ping-ponging some message over the wire protocol in a tight loop. Perhaps something related to vblank sync, which would explain why the screensaver would trigger the problem.