[PATCH libdrm 1/2] amdgpu: prevent an integer wraparound of cpu_map_count

[Marek Olšák]

On Tue, Oct 30, 2018, 11:52 AM Marek Olšák <maraeo at gmail.com> wrote:

>
>
> On Tue, Oct 30, 2018, 11:49 AM Marek Olšák <maraeo at gmail.com> wrote:
>
>>
>>
>> On Tue, Oct 30, 2018, 4:20 AM Michel Dänzer <michel at daenzer.net> wrote:
>>
>>> On 2018-10-29 10:15 p.m., Marek Olšák wrote:
>>> > You and I discussed this extensively internally a while ago. It's
>>> expected
>>> > and correct behavior. Mesa doesn't unmap some buffers and never will.
>>>
>>> It doesn't need to keep mapping the same buffer over and over again
>>> though, does it?
>>>
>>
>> It doesnt map it again. It just doesnt unmap. So the next map call just
>> returns the pointer. It's correct to stop the counter wraparound.
>>
>
> Mesa doesn't track whether a buffer is already mapped. Libdrm tracks that.
> It's a feature of libdrm to return the same pointer and expect infinite
> number of map calls.
>

Mesa has been having this optimization for 8 years. (since the radeon
winsys). It's surprising that it surprises you now.

Marek



> Marek
>
>
>> Marek
>>
>>
>>>
>>> --
>>> Earthling Michel Dänzer               |               http://www.amd.com
>>> Libre software enthusiast             |             Mesa and X developer
>>>
>>
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