Is core.internal.atomic.atomicFetchAdd implementation really lock free?

[max haughton]

On Wednesday, 30 November 2022 at 00:35:55 UTC, claptrap wrote:
> On Wednesday, 30 November 2022 at 00:16:00 UTC, rikki 
> cattermole wrote:
>> On 30/11/2022 1:12 PM, H. S. Teoh wrote:
>>> Hmm, that's weird that the docs would say that.  I've always 
>>> been under
>>> the impression that core.atomic ops use locks to achieve 
>>> atomicity.
>>
>> No its correct.
>>
>> As long as the hardware supports atomic operations, it'll use 
>> those instructions. It does have a fallback to use a mutex if 
>> need be though, which might be where you got that idea from.
>
> It really shouldn't do that IMO. People expect atomic ops to be 
> lock-free, it should be compile error if it cant be so.

I expect atomic ops to provide correct memory consistency, and 
preferably be atomic where the platform allows it.