On Thu, 2014-05-29 at 15:10 -0700, Ian Romanick wrote: > That code was originally added by: > > commit 061a3fe34051327fba418cc99599ecff0016ee15 > Author: Michel Dänzer <mic...@daenzer.net> > Date: Mon Aug 14 15:53:37 2006 +0000 > > Bug #7169: Attempt to make libGL symbols visible to drivers. > > Some applications end up dlopening libGL without RTLD_GLOBAL, so the libGL > symbols referenced by the driver can't be unresolved when libGL dlopens > it. > This attempts to make the libGL symbols visible to the driver by dlopening > libGL (again) with RTLD_GLOBAL before dlopening the driver and dlclosing > the obtained handle afterwards. > > So... I think that's not how dlopen always works. For other reasons, I > don't think the DRI drivers directly access symbols from libGL, so this > may be safe anyway. I'd want to see it tested, though.
Tested this with a cut-down version of glxdemo.c: http://people.freedesktop.org/~ajax/dlopen-glxdemo.c And with the dlopen of libGL removed indeed it doesn't DTRT: dmt:~% ./glxdemo libGL error: dlopen /usr/lib64/dri/i965_dri.so failed (/usr/lib64/dri/i965_dri.so: undefined symbol: _glapi_tls_Dispatch) libGL error: unable to load driver: i965_dri.so libGL error: driver pointer missing libGL error: failed to load driver: i965 Which I guess makes sense. The RTLD_LOCAL open of libGL means neither libGL nor its dependencies are made visible to other loaded objects, and libGL happens to be the only thing linked against libglapi. I think that's just a bug, the drivers should link against glapi as well. However just linking the drivers against glapi wouldn't necessarily mean we could eliminate the self-dlopen from libGL, because it would break the case of app doing dlopen(new libGL, LAZY) with an old driver. Is this a thing we actually care about? Can we not? In RHEL6 we have a package of Mesa 7.11 that just emits the DRI1 drivers for compatibility since we've rebased our real Mesa, but I'd be entirely happy to update mesa-dri1-drivers to be properly linked if we pulled this change into a future RHEL6 update. - ajax _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
