[Mesa-dev] [PATCH] Revert "glsl: don't reference shader prog data during cache fallback"

[Timothy Arceri]

On 17/05/17 22:03, Nicolai Hähnle wrote:
> On 17.05.2017 01:49, Timothy Arceri wrote:
>> This might work for gallium based drivers but I'm pretty sure this will
>> cause problems for the i965 fallback path.
> 
> What do those problems look like?

Sorry, I meant to add more details. The problem is that when the i965 
driver has a cache miss for a variant this could be happening long after 
link time. By this point we already have a reference and we also can't 
just reallocate the shader data because uniforms etc have most likely 
been set by this point.

> And any ideas on how to address the 
> issue then? There are a number of places that assume prog->sh.data is 
> non-NULL.

I'll need to take a closer look at the problem tomorrow. I'm not sure I 
understand why it is NULL, I thought the reference happens in the GLSL 
IR cache. Is it getting cleared somewhere by the tgsi pass?

> 
> Cheers,
> Nicolai
> 
> 
>>
>> On 17/05/17 04:40, Nicolai Hähnle wrote:
>>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>>
>>> This reverts commit 0e9991f957e296f46cfff40a94ffba0adf2a58e1.
>>>
>>> At least when we fallback because of TGSI, the gl_program objects are
>>> re-allocated, and we don't in fact already have a reference to the
>>> gl_shader_program_data.
>>>
>>> This fixes a crash that can be reproduced as follows:
>>>
>>> 1. Run any GL program with MESA_GLSL=cache_info.
>>> 2. Note the SHA of some tgsi_tokens.
>>> 3. Remove the corresponding file from ~/.cache/mesa and re-run.
>>>
>>> Cc: 17.1 <mesa-stable at lists.freedesktop.org>
>>> ---
>>>   src/compiler/glsl/linker.cpp | 3 +--
>>>   src/mesa/main/shaderobj.c    | 3 +--
>>>   2 files changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
>>> index 2e7dd2b..4776d09 100644
>>> --- a/src/compiler/glsl/linker.cpp
>>> +++ b/src/compiler/glsl/linker.cpp
>>> @@ -2243,22 +2243,21 @@ link_intrastage_shaders(void *mem_ctx,
>>>      struct gl_program *gl_prog =
>>>         ctx->Driver.NewProgram(ctx,
>>>
>>> _mesa_shader_stage_to_program(shader_list[0]->Stage),
>>>                                prog->Name, false);
>>>      if (!gl_prog) {
>>>         prog->data->LinkStatus = linking_failure;
>>>         _mesa_delete_linked_shader(ctx, linked);
>>>         return NULL;
>>>      }
>>>   -   if (!prog->data->cache_fallback)
>>> -      _mesa_reference_shader_program_data(ctx, &gl_prog->sh.data,
>>> prog->data);
>>> +   _mesa_reference_shader_program_data(ctx, &gl_prog->sh.data,
>>> prog->data);
>>>        /* Don't use _mesa_reference_program() just take ownership */
>>>      linked->Program = gl_prog;
>>>        linked->ir = new(linked) exec_list;
>>>      clone_ir_list(mem_ctx, linked->ir, main->ir);
>>>        link_fs_inout_layout_qualifiers(prog, linked, shader_list,
>>> num_shaders);
>>>      link_tcs_out_layout_qualifiers(prog, gl_prog, shader_list,
>>> num_shaders);
>>>      link_tes_in_layout_qualifiers(prog, gl_prog, shader_list,
>>> num_shaders);
>>> diff --git a/src/mesa/main/shaderobj.c b/src/mesa/main/shaderobj.c
>>> index 8a5fa5e..f6f7bf5 100644
>>> --- a/src/mesa/main/shaderobj.c
>>> +++ b/src/mesa/main/shaderobj.c
>>> @@ -427,22 +427,21 @@ _mesa_free_shader_program_data(struct gl_context
>>> *ctx,
>>>       /**
>>>    * Free/delete a shader program object.
>>>    */
>>>   void
>>>   _mesa_delete_shader_program(struct gl_context *ctx,
>>>                               struct gl_shader_program *shProg)
>>>   {
>>>      _mesa_free_shader_program_data(ctx, shProg);
>>> -   if (!shProg->data->cache_fallback)
>>> -      _mesa_reference_shader_program_data(ctx, &shProg->data, NULL);
>>> +   _mesa_reference_shader_program_data(ctx, &shProg->data, NULL);
>>>      ralloc_free(shProg);
>>>   }
>>>       /**
>>>    * Lookup a GLSL program object.
>>>    */
>>>   struct gl_shader_program *
>>>   _mesa_lookup_shader_program(struct gl_context *ctx, GLuint name)
>>>   {
>>>
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> 
>