Re: [PATCH v6 3/9] rust: sync: atomic: Add ordering annotation types

Boqun Feng
2025-07-10T14:43:00Z

On Thu, Jul 10, 2025 at 02:00:59PM +0200, Andreas Hindborg wrote:
> "Benno Lossin" <lossin@kernel.org> writes:
>
> > On Thu Jul 10, 2025 at 8:00 AM CEST, Boqun Feng wrote:
> >> Preparation for atomic primitives. Instead of a suffix like _acquire, a
> >> method parameter along with the corresponding generic parameter will be
> >> used to specify the ordering of an atomic operations. For example,
> >> atomic load() can be defined as:
> >>
> >> impl<T: ...> Atomic<T> {
> >> pub fn load<O: AcquireOrRelaxed>(&self, _o: O) -> T { ... }
> >> }
> >>
> >> and acquire users would do:
> >>
> >> let r = x.load(Acquire);
> >>
> >> relaxed users:
> >>
> >> let r = x.load(Relaxed);
> >>
> >> doing the following:
> >>
> >> let r = x.load(Release);
> >>
> >> will cause a compiler error.
> >>
> >> Compared to suffixes, it's easier to tell what ordering variants an
> >> operation has, and it also make it easier to unify the implementation of
> >> all ordering variants in one method via generic. The `TYPE` associate
> >> const is for generic function to pick up the particular implementation
> >> specified by an ordering annotation.
> >>
> >> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> >> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> >
> > One naming comment below, with that fixed:
> >
> > Reviewed-by: Benno Lossin <lossin@kernel.org>
> >
> >> ---
> >> rust/kernel/sync/atomic.rs | 3 +
> >> rust/kernel/sync/atomic/ordering.rs | 97 +++++++++++++++++++++++++++++
> >> 2 files changed, 100 insertions(+)
> >> create mode 100644 rust/kernel/sync/atomic/ordering.rs
> >
> >> +/// The trait bound for annotating operations that support any ordering.
> >> +pub trait Any: internal::Sealed {
> >
> > I don't like the name `Any`, how about `AnyOrdering`? Otherwise we
> > should require people to write `ordering::Any` because otherwise it's
> > pretty confusing.
>
> I agree with this observation.
>

I'm OK to do the change, but let me show my arguments ;-)

* First, we are using a language that supports namespaces,
so I feel it's a bit unnecessary to use a different name just because
it conflicts with `core::any::Any`. Doing so kinda undermines the
namespace concepts. And we may have other `Any`s in the future, are we
sure at the moment we should keyword `Any`?

* Another thing is that this trait won't be used very often outside
definition of functions that having ordering variants, currently the
only users are all inside atomic/generic.rs.

I probably choose the `ordering::Any` approach if you guys insist.

Regards,
Boqun

>
> Best regards,
> Andreas Hindborg
>
>
>