[Piglit] [PATCH 1/3] glx/glx-multithread-texture: Avoid uploading stale data to texture

[Thomas Hellstrom]

On 06/21/2017 05:16 PM, Brian Paul wrote:
> On 06/21/2017 06:25 AM, Thomas Hellstrom wrote:
>> the (tex->color != color) test, if false may cause uploading of stale
>> tex_data to the texture and cause a comparison failure. Also add a flush
>> after uploading so that texture data actually becomes visible for the 
>> draw
>> thread.
>>
>> Cc: Frank Henigman <fjhenigman at google.com>
>> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
>> ---
>>   tests/glx/glx-multithread-texture.c | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/tests/glx/glx-multithread-texture.c 
>> b/tests/glx/glx-multithread-texture.c
>> index 94ca1bc..c838fb7 100644
>> --- a/tests/glx/glx-multithread-texture.c
>> +++ b/tests/glx/glx-multithread-texture.c
>> @@ -113,10 +113,12 @@ load_func(void *arg)
>>           if (tex->color != color) {
>>               memset(tex_data, color, tex_bytes);
>>               tex->color = color;
>> +            glBindTexture(GL_TEXTURE_2D, tex->id);
>> +            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex_width,
>> +                     tex_height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
>> +                     tex_data);
>> +            glFlush();
>>           }
>> -        glBindTexture(GL_TEXTURE_2D, tex->id);
>> -        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex_width, tex_height,
>> -                 0, GL_RGBA, GL_UNSIGNED_BYTE, tex_data);
>>
>>           tex = advance(&count, LOAD);
>>       }
>>
>
> I'm surprised that wasn't found sooner.
>
> Reviewed-by: Brian Paul <brianp at vmware.com>
>
>

Actually, the (tex->color != color) test was, due to the number of 
textures, typically only false when the thread was spinning waiting for 
a new texture to become available, and then it had already initialized 
tex_data with the current color.

The fact that the flush wasn't needed before was due to the fact that on 
each spin waiting for a new texture, the code repeated the texture 
upload with the same data and eventually filled the command buffer, 
causing a flush....


/Thomas