Re: [PATCH] buffer: Avoid setting buffer bits that are already set

[Jens Axboe]

On 10/23/2017 07:25 PM, kemi wrote:
> 
> 
> On 2017å10æ24æ 09:21, Andi Kleen wrote:
>> kemi <kemi.wang@xxxxxxxxx> writes:
>>>
>>> I'll see if I can find some
>>>> time to implement the above in a nice way.
>>>
>>> Agree. Maybe something like test_and_set_bit() would be more suitable.
>>
>> test_and_set_bit is a very different operation for the CPU because
>> it is atomic for both. But we want the initial read to not
>> be atomic.
>>
> 
> I meant to express the meaning of test before setting bit.
> Apologize to make you confused.

That's why I suggested something like set_bit_if_not_set(),
test_and_set_bit() is both already used and has entirely
different semantics.

-- 
Jens Axboe