GLX software indirect rendering broken when used by more than one client

[Brian Paul]

Keith Packard wrote:
> Debugging a kernel scheduling issue, I tried running two glxgears at
> once without dri (option "NoDRI") and the X server neatly crashed on me.
> 
> in xm_dd.c:xmesa_update_state, ctx->DrawBuffer is NULL for the second
> GLX client. That certainly doesn't sound right.
> 
> I probably won't get back to looking at this for several days, so anyone
> should feel free to try and find the cause of this problem; it should be
> possible to use git-bisect to locate the patch causing the problem, but
> I have no idea how far back to start looking.

I've found/fixed the problem in Mesa.

-Brian