Bug 14675

Bug forwarded from launchpad.net, originally from the mythtv tracker:

Upstream MythTV indicated that this is actually a bug in mesa. Quoting on MythTV #4206: http://svn.mythtv.org/trac/ticket/4603

For anyone keeping score at home various myth threads open and close the display for local queries. Inside X11 this eventually works its way down to dri_glx.c::OpenDriver? which dlopen's the correct .so on the first call. Subsequent calls get the handle from that initial dlopen.

Unfortunately this doesn't increment the reference count for the .so and a dlclose at the first nested XOpenDisplay/XCloseDisplay (like in libmythtv's get_glx_version) causes the dri library to be unloaded and soon after that MythTV go boom. The unload message in the initial report turned out to be the key, something I realized moments after submitting the bug.

The quick fix, and this is Linux-specific, is to tweak the inital search at the top of OpenDriver? in mesa's dri_glx.c.

+--- mesa-7.0.2.orig/src/glx/x11/dri_glx.c	2008-02-21 18:37:58.000000000 -0600
++++ mesa-7.0.2/src/glx/x11/dri_glx.c	2008-02-21 18:39:13.000000000 -0600
+@@ -48,6 +48,7 @@
+ #include "dri_glx.h"
+ #include <sys/types.h>
+ #include <stdarg.h>
++#include <link.h>
+ 
+ #ifndef RTLD_NOW
+ #define RTLD_NOW 0
+@@ -198,6 +199,8 @@
+    for (driver = Drivers; driver; driver = driver->next) {
+       if (strcmp(driver->name, driverName) == 0) {
+          /* found it */
++         char *libPath = ((struct link_map *)(driver->handle))->l_name;
++         dlopen(libPath, RTLD_NOW | RTLD_GLOBAL);
+          return driver;
+       }
+    }