Xvfb problems with OpenGL feedback buffer

[Brian Paul]

Joe Miller wrote:
> Hi,
> 
> I'm having some problems running an opengl application in Xvfb, where
>  the Xvfb server keeps dying. After some investigation, it looks like the
>  problem occurs when I change the glFeedbackBuffer size from something
>  very large (on order of 40,000,000 floating point array) to something
>  smaller (4,000,000) and then change the glRenderMode from GL_FEEDBACK to
>  GL_RENDER. I've included a small program below, which I think displays
>  the problem I'm having (note this program was written explicitly to
>  flush out the problems I'm having). While the program below segv's when I
>  try to run it in Xvfb, a much more involved program where I first
>  discovered the issue returns the following error message
>    ChipsServer: Fatal IO error 14 (Bad address) on X server :6966.0.
> Both seemed to be caused by the same issue. I don't have any problems
>  running either program with the standard X-Server. The problem only
>  happens with a very large buffer size. I'm running on Redhat Enterprise 8,
>  using X.Org version 6.8.2. 
> 
> I'd appreciate any thoughts or suggestions. If you need any more
>  information please let me know.

Looks like a GLX protocol encode or decode bug.  Seems to work fine with 
stand-alone Mesa and direct rendering.

I may not get around to investigating for a bit though.  Perhaps you 
could file a Mesa bug report so it doesn't get lost.

-Brian