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

[Tapani Pälli]

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!

// Tapani