In article <200705201059.l4KAxsPs009546@wheel.duzan.org>,
Gary Duzan  <gary@duzan.org> wrote:
>   I have noticed that my X session is prone to crashing with a
>current kernel on my amd64 multiprocessor box. Running "x11perf
>-all" and waiting a few minutes seems to be sufficient to cause
>the problem. I noticed it both before and after upgrading userland,
>so it seems likely to be a kernel problem.

It is from the fs/gs changes. Revert those...

christos