Hi, I'm just forwarding to you a bug report originally made against Firefox:
https://bugzilla.mozilla.org/show_bug.cgi?id=973192

The symptom is Firefox freezing on startup. The cause (see around comment
39--42 on that bug) is that a XCloseDisplay() call takes about one minute to
return.

The original reporter of the bug has recorded a profile which shows time spent
in nouveau_dri.so (see comments 50, 51 on the mozilla bug)

If you want to see what the application code triggering this bug looks like,
it's all self-contained in this file:

http://hg.mozilla.org/mozilla-central/file/tip/toolkit/xre/glxtest.cpp

   228   glXMakeCurrent(dpy, None, nullptr);
   229   glXDestroyContext(dpy, context);
   230   XDestroyWindow(dpy, window);
   231   XFreeColormap(dpy, swa.colormap);
   232   XCloseDisplay(dpy);  // <--- this XCloseDisplay call takes 1 minute
   233   dlclose(libgl);

Is there some more information that you need, that isn't already on the mozilla
bug?

Is this application code doing something evil here?

Is this a known issue? Do you have a guess as to whether it might affect many
users (i.e., should we try working around it)?