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

[Ian Romanick]

On 08/05/2016 07:05 PM, ⚛ wrote:
> On Sat, Aug 6, 2016 at 3:37 AM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
>> On Sat, 2016-08-06 at 02:42 +0200, Jan Ziak 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.
>>
>> this is IMO micro-optimization in the wrong place. RTLD_NOW also
>> guarantees that symbols were successfully resolved. Changing it to lazy
>> may hide bugs by deferring failure to future point in the execution.
> 
> Question 1: Are you suggesting to replace current RTLD_LAZY in all
> locations with RTLD_NOW?
> 
> Question 2: Exists there a reason for _not_ linking radeonsi_dri.so,
> swrastg_dri.so, etc, directly to Mesa's libGL.so? The Gallium
> *_dri.so libraries are the same inode on the filesystem.

This is an intentional feature.  This allows libGL and *_dri.so to be
installed from different versions.  It also allows the possibility for a
*_dri.so from outside the Mesa source tree.

> Question 3: Isn't the current status quo (i.e: not linking
> radeonsi_dri.so directly to libGL.so) also a micro-optimization that
> can hide certain bugs?
> 
> Question 4: Is it planned for *_dri.so belonging to Gallium/DRI _not_
> to be mapped to the same inode on the filesystem in the future? If
> there is no such plan, what was the original point of having multiple
> _dri.so files mapped to the same inode?
> 
> Thanks.
>