[Mesa-dev] [PATCH v4 (part2) 04/56] i965: set ARB_shader_storage_buffer_object related constant values

[Samuel Iglesias Gonsálvez]

On 03/09/15 14:08, Tapani Pälli wrote:
> 
> 
> On 09/03/2015 03:05 PM, Iago Toral wrote:
>> On Thu, 2015-09-03 at 13:52 +0300, Tapani Pälli wrote:
>>>
>>> On 09/03/2015 01:40 PM, Samuel Iglesias Gonsálvez wrote:
>>>>
>>>>
>>>> On 03/09/15 12:30, Tapani Pälli wrote:
>>>>> Hi;
>>>>>
>>>>> On 07/23/2015 09:42 AM, Samuel Iglesias Gonsalvez wrote:
>>>>>> v2:
>>>>>> - Add tessellation shader constants assignment
>>>>>>
>>>>>> Signed-off-by: Samuel Iglesias Gonsalvez <siglesias at igalia.com>
>>>>>> ---
>>>>>>     src/mesa/drivers/dri/i965/brw_context.c | 12 ++++++++++++
>>>>>>     1 file changed, 12 insertions(+)
>>>>>>
>>>>>> diff --git a/src/mesa/drivers/dri/i965/brw_context.c
>>>>>> b/src/mesa/drivers/dri/i965/brw_context.c
>>>>>> index b08a53b..a5c7b91 100644
>>>>>> --- a/src/mesa/drivers/dri/i965/brw_context.c
>>>>>> +++ b/src/mesa/drivers/dri/i965/brw_context.c
>>>>>> @@ -551,6 +551,18 @@ brw_initialize_context_constants(struct
>>>>>> brw_context *brw)
>>>>>>        ctx->Const.TextureBufferOffsetAlignment = 16;
>>>>>>        ctx->Const.MaxTextureBufferSize = 128 * 1024 * 1024;
>>>>>>
>>>>>> +   /* FIXME: Tessellation stages are not yet supported in i965, so
>>>>>> +    * MaxCombinedShaderStorageBlocks doesn't take them into account.
>>>>>> +    */
>>>>>> +   ctx->Const.Program[MESA_SHADER_VERTEX].MaxShaderStorageBlocks
>>>>>> = 12;
>>>>>> +  
>>>>>> ctx->Const.Program[MESA_SHADER_GEOMETRY].MaxShaderStorageBlocks = 12;
>>>>>> +  
>>>>>> ctx->Const.Program[MESA_SHADER_TESS_EVAL].MaxShaderStorageBlocks = 0;
>>>>>> +  
>>>>>> ctx->Const.Program[MESA_SHADER_TESS_CTRL].MaxShaderStorageBlocks = 0;
>>>>>> +  
>>>>>> ctx->Const.Program[MESA_SHADER_FRAGMENT].MaxShaderStorageBlocks = 12;
>>>>>> +   ctx->Const.Program[MESA_SHADER_COMPUTE].MaxShaderStorageBlocks
>>>>>> = 12;
>>>>>> +   ctx->Const.MaxCombinedShaderStorageBlocks = 12 * 3;
>>>>>> +   ctx->Const.MaxShaderStorageBufferBindings = 48;
>>>>>
>>>>> I think there is something funny with MaxShaderStorageBufferBindings
>>>>> value calculation. Commit 28ef0f83 adds 12 to it and then this commit
>>>>> overwrites it as 48. Without compute shaders I guess this value should
>>>>> be 48 - 12?
>>>>>
>>>>> I guess earlier '+12' should be removed and this part should be
>>>>> modified
>>>>> to calculate based on what is supported. For me '48 -12' fixes a few
>>>>> crashes I'm getting with
>>>>> "igalia/wip/siglesias/ARB_shader_storage_buffer_object-v4.3" branch
>>>>> I've
>>>>> used for some testing.
>>>>>
>>>>
>>>> I see. We are going to review the MaxShaderStorageBufferBindings
>>>> calculation, thanks for the report and the ideas.
>>>>
>>>> Can you share with us the tests that crashed because of this? You can
>>>> send them privately to me, if needed.
>>>
>>> These are some Piglit tests that use buffer objects. Crash happens at
>>> _mesa_free_buffer_objects(), it's not quite clear yet to me why (maybe
>>> memory gets trashed) but I bisected it to this commit changing
>>> MaxShaderStorageBufferBindings. For example
>>> 'arb_framebuffer_no_attachments-atomic' segfaults when destroying the
>>> context and calling _mesa_free_buffer_objects().
>>>
>>> Here's example backtrace:
>>> (gdb) bt
>>> #0  0x00007ffff3dae830 in pthread_mutex_lock () from
>>> /lib64/libpthread.so.0
>>> #1  0x00007ffff1da8681 in mtx_lock (mtx=0xffffffffffffffff) at
>>> ../../include/c11/threads_posix.h:192
>>> #2  _mesa_reference_buffer_object_ (ctx=0x7ffff7fd0040,
>>> ptr=0x7ffff7ff13d0, bufObj=0x0) at main/bufferobj.c:450
>>> #3  0x00007ffff1da9173 in _mesa_reference_buffer_object (bufObj=0x0,
>>> ptr=<optimized out>, ctx=0x7ffff7fd0040) at main/bufferobj.h:123
>>> #4  _mesa_free_buffer_objects (ctx=ctx at entry=0x7ffff7fd0040) at
>>> main/bufferobj.c:907
>>> #5  0x00007ffff1db553b in _mesa_free_context_data
>>> (ctx=ctx at entry=0x7ffff7fd0040) at main/context.c:1342
>>> #6  0x00007ffff2077a3e in intelDestroyContext (driContextPriv=0x6392f0)
>>> at brw_context.c:996
>>>
>>> it crashes because 'oldObj' in _mesa_reference_buffer_object_ points to
>>> 0xffffffffffffffff.
>>
>> Thanks for reporting this, the problem with the crash is that there is a
>> mismatch between the number of bindings used by the driver and the
>> maximum declared by Mesa, this was actually a silly mistake we
>> introduced after updating some of our code during reviews. To fix this
>> you need to set MAX_SHADER_STORAGE_BUFFERS in src/mesa/main/config.h to
>> 15 (instead of the current value of 7, the issue comes from 7*6 = 42 <
>> 48).
>>
>> Samuel is going to look into the +12 issue you also mentioned.
> 
> OK thanks!
> 

You were right: we were overwriting MaxShaderStorageBufferBindings and
the +12 was lost. I modified this patch to set
MaxShaderStorageBufferBindings = 36 and later add the +12 if
ARB_compute_shader is enabled.

Jordan, this patch already had your R-b but we modified it a little bit
to fix this bug. Once we have a final version of the patch series with
all changes and fixes, we will contact you to talk about what to do with
this patch (keep your R-b or not) and others, in order to facilitate the
review.

Thanks!

Sam

> // Tapani
>