(In reply to comment #31)
> Created attachment 101350 [details]
> GDB log with "dup fd..." patch
> 
> It works!

Great! Also I just figured out why this is happening to you and not to anyone
else. It's the dual screens! (Who uses separate screens anyways...)

src/glx/glxext.c allocates a screen per... screen. And then when it cleans up,
it deletes the screens in the same order it created them. So it's precisely the
scenario I outlined, where by the time the second screen goes to be destroyed,
the fd it relies on (which is the first one) has already been closed.

I'll push this patch out and tag it for 10.2.