[libcamera-devel] [RFC PATCH 5/6] android: camera_device: Add thread safety annotation

[Umang Jain]

Hi Hiro,

On 11/29/21 5:08 PM, Hirokazu Honda wrote:

<snip>
>
>>
>> Well, the document currently states that ACQUIRED_AFTER is currently
>> un-implemented.
>>
> Oh I don't know that. What document do you refer?
> I couldnm't find it in
> https://clang.llvm.org/docs/ThreadSafetyAnalysis.html#acquired-before-acquired-after.


https://clang.llvm.org/docs/ThreadSafetyAnalysis.html#acquired-before-and-acquired-after-are-currently-unimplemented

>
>> Secondly, I don't think we enforce a design interaction between the two
>> mutexes currently, that requires this macro. For e.g.
>> completeDescriptor() on a requestcomplete() path, will acquire
>> descriptorsMutex_ irrespective of acquiring stateMutex_. Is there any
>> strong reasoning I am missing which led to use of ACQUIRED_AFTER for
>> descriptorsMutex_?
>>
> No strong reason. I think it is nicer to clarify the order.
>
>  From the code, I think this is the current order used in code.


Makes sense.

>
> Thanks,
> -Hiro
>>> +     std::queue<std::unique_ptr<Camera3RequestDescriptor>> descriptors_ GUARDED_BY(descriptorsMutex_);
>>
>> This is becoming a bit harder to read (not your fault, probably mine). I
>> should spend some time tinkering on naming these members/classes.
>>
>>>        std::string maker_;
>>>        std::string model_;