[RFC 2/2] rust: sync: Add atomic support

[Boqun Feng]

On Fri, Jun 14, 2024 at 11:59:58AM +0200, Miguel Ojeda wrote:
> On Thu, Jun 13, 2024 at 9:05 PM Boqun Feng <boqun.feng at gmail.com> wrote:
> >
> > Does this make sense?
> 
> Implementation-wise, if you think it is simpler or more clear/elegant
> to have the extra lower level layer, then that sounds fine.
> 
> However, I was mainly talking about what we would eventually expose to
> users, i.e. do we want to provide `Atomic<T>` to begin with? If yes,

The truth is I don't know ;-) I don't have much data on which one is
better. Personally, I think AtomicI32 and AtomicI64 make the users have
to think about size, alignment, etc, and I think that's important for
atomic users and people who review their code, because before one uses
atomics, one should ask themselves: why don't I use a lock? Atomics
provide the ablities to do low level stuffs and when doing low level
stuffs, you want to be more explicit than ergonomic.

That said, I keep an open mind on `Atomic<T>`, maybe it will show its
value at last. But right now, I'm not convinced personally.

> then we could make the lower layer private already.
> 
> We can defer that extra layer/work if needed even if we go for
> `Atomic<T>`, but it would be nice to understand if we have consensus
> for an eventual user-facing API, or if someone has any other opinion
> or concerns on one vs. the other.
> 

Yes, that'll be great. I'd love to see others' inputs!

Regards,
Boqun

> Cheers,
> Miguel