[Mesa-dev] [PATCH 0/6] st/mesa: add locking around lazy texture/sampler updates

[Nicolai Hähnle]

On 07.10.2017 00:36, Roland Scheidegger wrote:
> I can't help but think that there'd be none of those problems if those
> views were actually used as specced by gallium initially: all sampler
> views (and surfaces) are per context, and they simply cannot be used in
> another context.

That is actually the case today, with the exception that when a texture 
object is destroyed, all of sampler views are destroyed as well, from 
within whatever happens to be the current context. (This can be solved 
with some kind of "orphaned" list, but I'd rather not do that in st/mesa.)

The problem is that when we need a sampler view for a texture, we have 
(a) the context pointer and (b) the texture object pointer, and we need 
to map those to a sampler view. This happens via a mutable per-texture 
object structure, access to which must be protected somehow.

Cheers,
Nicolai


> 
> Roland
> 
> Am 06.10.2017 um 22:38 schrieb Nicolai Hähnle:
>> Hi all,
>>
>> This series is a first result of debugging some random crashes in dEQP's
>> multi-threaded EGL tests.
>>
>> The OpenGL spec is pretty clear that application must not modify a texture
>> in one context while simultaneously using it for texturing (or even
>> modifying) it in another context. Texturing simultaneously in multiple
>> contexts is fine, though.
>>
>> This can lead to races when st_finalize_texture is called simultaneously
>> for two contexts, or if two contexts simultaneously attempt to access the
>> sampler view array of a texture.
>>
>> This series should fix most (all?) issues where our internal data
>> structures could become corrupted. I am aware of one remaining corner
>> case that could lead to rendering corruption. It appears rather non-trivial
>> to fix, and it is documented in a comment of patch #5.
>>
>> Please review!
>> Thanks,
>> Nicolai
>> --
>>   src/gallium/auxiliary/util/u_inlines.h   |  16 ++-
>>   src/gallium/include/pipe/p_context.h     |  10 ++
>>   src/mesa/state_tracker/st_atom_sampler.c |  12 +-
>>   src/mesa/state_tracker/st_atom_texture.c |  12 --
>>   src/mesa/state_tracker/st_cb_texture.c   |  59 +++++++--
>>   src/mesa/state_tracker/st_manager.c      |   3 +
>>   src/mesa/state_tracker/st_sampler_view.c | 137 +++++++++++++++++----
>>   src/mesa/state_tracker/st_sampler_view.h |   7 ++
>>   src/mesa/state_tracker/st_texture.h      |  23 +++-
>>   9 files changed, 205 insertions(+), 74 deletions(-)
>>
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>>
> 


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