Multiple GLX Contexts, Crashing X

I’ve been fighting this on and off for the last couple of years through various versions of X and different drivers (nv, nVidia, others) on various hardware, etc. The problem has been elusive and I haven’t been able to find the root cause.

My application suite has multiple programs using Motif GLX Widgets. Most programs have a single GLX Context; some have two. All are themselves single-threaded applications using X/Motif/GLX.

I’ve got infrequent but catastrophic X Server crashes (Segmentation Violations) when closing application windows. In my “close” callbacks, I’ve tried:

  • Just exiting (crashes X sometimes)
  • Using XRaiseWindow, then exiting (crashes less!)
  • Carefully destroying GLXContext, then exiting (still crashes)
  • Carefully setting the current context before destroying (still crashes)
  • Carefully setting the current context to NULL before destroying (still crashes)

Crashes seem to typically be 1 out of 10 kinds of frequency. It nearly always involves closing a window that is not popped to the top (like with focus-follows-pointer + keyboard accelerators).

Under Redhat 7.2, the crashes were frequent when using the “nv” driver, but disappeared when using the nVidia-supplied driver. Under Redhat Enterprise Linux 3, I get the crashes using build
5328 from nVidia.

When trying to track this down in the past using an X Server built in debug, the crash then “seemed” to be related to not-fully-released GLX context information, but I can’t be more specific than that. Running X in verbose mode does not yield any helpful information.

“Simple” programs to demonstrate the problem have not been easy to come up with.

Is there a golden path to walk with regard to leaving an application to make sure the GLX part of the X Server is fully cleaned-up, flushed and varnished before calling exit()?

Anyone experienced something similar and found a root cause?

I don’t really know, I don’t want to make fast conclusions as I don’t really understand your cause, but this seems a glx problem in fact.

I understand that: you run glx/motif single-threaded programs, and those programs crash when on some specific situations (Nvidia but no Nvidia drivers…). Your programs don’t share any context (as it’s not possible) of course.

The problem with Nvidia cards could be possible.

Regarding the official glx spec, only glx 1.3 is OpenGL 1.2 compliancy… so… only Nvidia drivers (at my known) support glx 1.3.

Hope this helps.

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