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

Benno Lossin
2025-07-10T11:08:26Z

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.

---
Cheers,
Benno

> + /// Describes the exact memory ordering.
> + const TYPE: OrderingType;
> +}