[cairo] Debugging cairo-related X hangs

[Boris Zbarsky]

Recently, I've been running into numerous hangs in the X server while running 
cairo-based Gecko builds (things like print preview, lots of very simple SVG 
pages, etc).

Unfortunately, I haven't been able to figure out a way to debug these.  Even 
running with -sync, a profiler (I've tried several) just shows X using the time, 
without the callstack coming back into Gecko code...

The problem is compounded by the fact that folks with newer X versions (I have 
the one that comes with Fedora Core 4) don't see the problem, which means the 
Fedora and X people aren't going to spend time on it.

Does anyone have any idea how we could get to the bottom of what's going on 
here?  Fedora may not care about FC4 users, but those of us shipping cairo-based 
applications sort of have to.  :(

Thanks in advance,
-Boris