[Mesa-dev] [PATCH v3 1/1] clover: use pipe_resource references

[Francisco Jerez]

Vedran Miletić <vedran at miletic.net> writes:

> On 03/17/2017 05:20 AM, Jan Vesely wrote:
>> On Thu, 2017-03-16 at 18:07 -0700, Francisco Jerez wrote:
>>> Jan Vesely <jan.vesely at rutgers.edu> writes:
>>>
>>>> On Thu, 2017-03-16 at 17:22 -0700, Francisco Jerez wrote:
>>>>> Jan Vesely <jan.vesely at rutgers.edu> writes:
>>>>>
>>>>>> On Thu, 2017-03-16 at 15:24 -0700, Francisco Jerez wrote:
>>>>>>> Jan Vesely <jan.vesely at rutgers.edu> writes:
>>>>>>>
>>>>>>>> v2: buffers are created with one reference.
>>>>>>>> v3: add pipe_resource reference to mapping object
>>>>>>>>
>>>>>>>
>>>>>>> Mapping objects are supposed to be short-lived, they're logically part
>>>>>>> of the parent resource object so they shouldn't ever out-live it.  What
>>>>>>> is this useful for?
>>>>>>
>>>>>> currently they can outlive the underlying pipe_resource. pipe_resource
>>>>>> is destroyed in root_resource destructor, while the list of mappings is
>>>>>> destroyed after resource destructor.
>>>>>
>>>>> Right.  I guess the problem is that the pipe_transfer object associated
>>>>> to the clover::mapping object holds a pointer to the backing
>>>>> pipe_resource object but it fails to increment its reference count?  I
>>>>> guess that's the reason why v2 didn't help?
>>>>
>>>> yes, though the pointer is hidden somewhere. I thought pxfer->resource
>>>> might be it, but it's not, and digging deeper into the structure didn't
>>>> sound like a good idea to me.
>>>>
>>>
>>> What is pxfer->resource about in that case?
>> 
>> that's a good question, so I did a bit of digging. for EG global
>> buffers are shadowed in global buffer memory pool, so mapping uses
>> memory pool's pipe_resource. I'm still not 100% sure where exactly
>> unmapping the global pool accesses the original buffer's pipe_resource,
>> but I don't think it matters that much. It's not required for pxfer-
>>> resource to be equal to resource->pipe. we need to guarantee that
>> resource->pipe outlives all mappings.
>> either explicitly, or by grabbing reference.
>> 
>> Jan
>> 
>
> Jan's v3 solves the problem, as does my version.
>
> Francisco, do you have a particular preference how should we proceed?
>

I'm okay either way -- Though I'll send some codestyle-related
suggestions to Jan's patch in a minute.

> Regards,
> Vedran
>
> -- 
> Vedran Miletić
> vedran.miletic.net
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