(In reply to comment #2)
> (In reply to comment #1)
> > Please attach the Xorg.0.log file and the output of dmesg and glxinfo.
> 
> Unfortunately I was not able to reproduce this issue again. For being clear,
> it just happened once in the last two or three months.

Ugh, that makes it hard to do anything about the problem, or even confirm that
it's fixed...

> I am using awesome 3.4.15.

AFAICT awesome doesn't support compositing itself, so unless you're explicitly
running a separate compositing manager, you're probably not using compositing.

So, assuming the problem is that the evolution process hangs,
http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/commit/?id=c4ae0e2cbcc0e2ebf9f13ee92d59b5120254a1dc
might help.

Or it might not be related to the graphics stack at all.