[Mesa-dev] [PATCH] src: replace RTLD_NOW with RTLD_LAZY

[Jan Vesely]

On Sat, 2016-08-06 at 07:24 -0700, Jason Ekstrand wrote:
> On Aug 6, 2016 4:00 AM, "⚛" <0xe2.0x9a.0x9b at gmail.com> wrote:
> > 
> > 
> > On Sat, Aug 6, 2016 at 4:34 AM, Rob Clark <robdclark at gmail.com>
> > wrote:
> > > 
> > > On Fri, Aug 5, 2016 at 8:42 PM, Jan Ziak <0xe2.0x9a.0x9b at gmail.co
> > > m>
> wrote:
> > 
> > > 
> > > > 
> > > > Mesa source code prior to this patch uses both RTLD_NOW and
> > > > RTLD_LAZY.
> > > > This patch removes all RTLD_NOW in favor of RTLD_LAZY.
> > > > 
> > > > In comparison to early binding, lazy binding reduces CPU
> > > > instruction
> count
> > 
> > > 
> > > > 
> > > > of small GL apps (e.g: glxinfo) by 6 million instructions.
> > > > Larger apps won't notice the difference.
> > > 
> > > tbh, I don't know the background of existing places that use
> > > RTLD_LAZY
> > > instead of RTLD_NOW (but my experience w/ xserver using LAZY has
> > > not
> > > been positive, so I think going the other direction seems like a
> > > good
> > > idea)..
> > 
> > We could add a verifier to the build process that tests the
> > foo_dri.so
> > libraries (as well as all other libs subject to dlopen by Mesa) for
> > undefined symbols:
> > 
> > $ LD_PRELOAD=libGL.so ldd -d -r radeonsi_dri.so \
> >     | grep "^undefined" && echo "red alert!"
> > 
> > This will ensure that Mesa does not break apps after replacing all
> > RTLD_NOWs with RTLD_LAZY.
> > 
> > I am going to start writing a new patch verifying relevant *.so
> > files
> > at buildtime.
> 
> Yes please. Regardless of whether or not we use RTLD_LAZY, I would
> like
> undefined symbols to produce a build error rather than a runtime
> error you
> need extra environment variables to debug.

this is done by using -Wl,--no-undefined (and afaik, it has been in use
for some time now), no need to introduce local tool

Jan

> 
> > 
> > > 
> > > But I'm not sure that optimizing for glxinfo is the best goal.
> > 
> > I will turn my attention to manifestations of suboptimal Mesa GL in
> > other apps as soon as I am satisfied with glxinfo/glxgears (and
> > after
> > the list of my patches at patchwork gets closer to zero).
> > _______________________________________________
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> > mesa-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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-- 
Jan Vesely <jan.vesely at rutgers.edu>
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