RE: rte_atomic_*_explicit

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> On Thu, Jan 25, 2024 at 11:10:47PM +0100, Morten Br�rup wrote:
> > > From: Mattias R�nnblom [mailto:hofors@lysator.liu.se]
> > > Sent: Thursday, 25 January 2024 19.54
> > >
> > > Why do rte_stdatomic.h functions have the suffix "_explicit"?
> > > Especially
> > > since there aren't any wrappers for the implicit variants.
> > >
> > > More to type, more to read.
> >
> > They have the "_explicit" suffix to make their names similar to those in
> stdatomic.h.
> >
> > You might consider their existence somewhat temporary until C11 stdatomics
> can be fully phased in, so there's another argument for similar names. (This
> probably does not happen as long as compilers generate slower code for C11
> stdatomics than with their atomic built-ins.)
> 
> yes, there was feedback at the time it was.
> 
> * we should *not* have non-explicit versions of the macros
> * the atomic generic functions should be named to match C11 standard
>   with a rte_ prefix.
This was mainly done to ensure that users think through the memory ordering they want to use. This also matches with the compiler atomic built-ins. Without explicit, it is sequentially consistent memory order.

> 
> >
> > >
> > > When was this API introduced? Shouldn't it say "experimental"
> > > somewhere?
> >
> > They were introduced as part of the migration to C11.
> > I suppose they were not marked experimental because they replaced
> something we didn't want anymore (the compiler built-ins for atomics, e.g.
> __atomic_load_n()). I don't recall if we discussed experimental marking or not.
> 
> i don't think we discussed it since they're wrapper macros.
> 
> >
> >
> > Reverse paper trail:
> > https://git.dpdk.org/dpdk/log/lib/eal/include/rte_stdatomic.h
> > https://patchwork.dpdk.org/project/dpdk/patch/1692738045-32363-2-git-
> send-email-roretzla@linux.microsoft.com/
> > https://patchwork.dpdk.org/project/dpdk/patch/1692738045-32363-2-git-
> send-email-roretzla@linux.microsoft.com/
> >