Stack trace?  Is the seg fault occurring in VirtualGL?

On 4/23/10 9:40 AM, Shree Kumar wrote:
> Thanks, DRC ! VirtualGL/TurboVNC make VizStack useful too :-)
> 
> I have been trying this out. pbdemo works, no problems there. Other
> than the fact that it overwrote another PPM file ;-)
> 
> So I look deeper into the source code of the equalizer library(
> http://www.equalizergraphics.com/) ; I'm running
> the eqPly program now.
> 
> The app does multiple calls to glXChooseVisual, some of which return
> NULL. But the last few don't.
> 
> However, the segfault happens in some code which looks like :
> 
> int nConfigs = 0;
> GLXFBConfig * configs = glXGetFBConfigs(display, screen, &nConfigs); <--
> segfault !
> 
> The "display" value is OK, and "screen" is 0. I'm still debugging with the
> source code, but any hints would be very useful !
> 
> Thanks
> -- Shree
> 
> On Fri, Apr 23, 2010 at 7:04 PM, DRC <[email protected]
> <mailto:[email protected]>> wrote:
> 
>     Oops, I apparently glazed over that part of the original message.  :)
>     VizStack looks very cool.
> 
>     If pbdemo works, then please send the source code for the app that is
>     failing, and I'll try it out here.  That warning message from VirtualGL
>     is printed in glXChooseVisual() and is typically caused by one of three
>     things:
> 
>     -- The 2D X server doesn't have a 24-bit visual available
>     -- The 3D X server (:15 in your case) doesn't have a 24-bit or 32-bit FB
>     config available
>     -- The 3D X server doesn't have an FB config available that supports
>     Pbuffers
> 
>     This warning message is printed whenever VirtualGL can't obtain an
>     appropriate 24-bit or 32-bit Pbuffer-enabled FB config to map to the
>     visual that the app is requesting.  The warning basically says-- the
>     application is probably about to print an error message and fail.  In
>     your case, the application appears to be subsequently seg faulting,
>     which isn't good.  It may not be properly checking for a NULL return
>     value from glXChooseVisual().
> 
>     On 4/22/10 10:31 PM, Shree Kumar wrote:
>     >
>     > Yes, I have set VGL_DISPLAY before using vglrun.
>     >
>     > I'm on a 6 GPU box. The piece of software I'm writing (VizStack,
>     mentioned
>     > below) dynamically manages the X servers. I see some mails in the list
>     > asking about how to use VirtualGL with multiple GPUs. VizStack
>     will meet
>     > their needs on single nodes as well as on cluster of nodes.
>     >
>     > VizStack maintains pools of X servers, so I end up with :15 !
>     >
>     > I will try running mesademos/pbdemo.c.
>     >
>     > Thanks
>     > -- Shree
>     >
>     > On Thu, Apr 22, 2010 at 8:33 PM, DRC
>     <[email protected]
>     <mailto:[email protected]>
>     > <mailto:[email protected]
>     <mailto:[email protected]>>> wrote:
>     >
>     >     VirtualGL should run fine with applications that use Pbuffers.
>     >     mesademos/pbdemo.c in the VirtualGL source tree demonstrates this.
>     >     There is apparently something else wrong here.
>     >
>     >     The fact that your 3D X server is :15 is unusual.  The 3D X
>     server is
>     >     typically :0.0, although it may be :0.1 or :0.2 if you have
>     multiple 3D
>     >     graphics cards.  Did you override the default value of
>     VGL_DISPLAY?  If
>     >     so, why did you set it to :15?
>     >
>     >     On 4/22/10 5:38 AM, Shree Kumar wrote:
>     >     > Hi,
>     >     >
>     >     > I've been using TurboVNC/VirtualGL as a remote access mechanism;
>     >     we also
>     >     > provide it as a remote access method with VizStack
>     >     > (http://www.vizstack.sourceforge.net)
>     >     >
>     >     > In my setup, "vglrun glxgears" works fine. However, an
>     application
>     >     which
>     >     > uses Pbuffers itself fails. e.g.
>     >     >
>     >     > sh...@servergfx:~/equalizer-release-0.9.1/examples/configs$
>     vglrun
>     >     eqPly
>     >     > -m ~/happy.ply
>     >     > [VGL] WARNING: VirtualGL attempted and failed to obtain a
>     >     Pbuffer-enabled
>     >     > [VGL]    24-bit visual on the 3D X server :15.  If the
>     application
>     >     > [VGL]    subsequently fails, then make sure that the 3D X
>     server is
>     >     > configured
>     >     > [VGL]    for 24-bit color and has accelerated 3D drivers
>     installed.
>     >     > Segmentation fault
>     >     > sh...@servergfx:~/equalizer-release-0.9.1/examples/configs$
>     >     >
>     >     > In this case, equalizer is trying to create a pbuffer for
>     rendering.
>     >     >
>     >     > Any hints on what could be going wrong here ?
>     >     >
>     >     > Thanks
>     >     > -- Shree
>     >     > http://vizstack.sourceforge.net/
>     >     > http://www.shreekumar.in/
>     >     >
>     >     >
>     >     >
>     >     >
>     >    
>     
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> -- 
> http://www.shreekumar.in/
> 
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