linux-kernel - Re: [PATCH v7 3/9] rust: sync: atomic: Add ordering annotation types

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <DBBP3E8PZ81U.2O0QHK1GQXKX2@kernel.org>
Date: Mon, 14 Jul 2025 12:10:46 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Boqun Feng" <boqun.feng@...il.com>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <lkmm@...ts.linux.dev>,
 <linux-arch@...r.kernel.org>
Cc: "Miguel Ojeda" <ojeda@...nel.org>, "Alex Gaynor"
 <alex.gaynor@...il.com>, "Gary Guo" <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "Danilo Krummrich" <dakr@...nel.org>,
 "Will Deacon" <will@...nel.org>, "Peter Zijlstra" <peterz@...radead.org>,
 "Mark Rutland" <mark.rutland@....com>, "Wedson Almeida Filho"
 <wedsonaf@...il.com>, "Viresh Kumar" <viresh.kumar@...aro.org>, "Lyude
 Paul" <lyude@...hat.com>, "Ingo Molnar" <mingo@...nel.org>, "Mitchell Levy"
 <levymitchell0@...il.com>, "Paul E. McKenney" <paulmck@...nel.org>, "Greg
 Kroah-Hartman" <gregkh@...uxfoundation.org>, "Linus Torvalds"
 <torvalds@...ux-foundation.org>, "Thomas Gleixner" <tglx@...utronix.de>,
 "Alan Stern" <stern@...land.harvard.edu>
Subject: Re: [PATCH v7 3/9] rust: sync: atomic: Add ordering annotation
 types

On Mon Jul 14, 2025 at 7:36 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@...gle.com>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> ---
> Benno, please take a good and if you want to provide your Reviewed-by
> for this one. I didn't apply your Reviewed-by because I used
> `ordering::Any` instead of `AnyOrdering`, I think you're Ok with it [1],
> but I could be wrong. Thanks!
>
> [1]: https://lore.kernel.org/rust-for-linux/DB8M91D7KIT4.14W69YK7108ND@kernel.org/

> +/// The trait bound for annotating operations that support any ordering.
> +pub trait Any: internal::Sealed {

How about we just name this `Ordering`? Because that's what it is :)

That sadly means you can't do

    fn foo<Ordering: Ordering>() {}
           --------  ^^^^^^^^ not a trait
           |
           found this type parameter

But you can still do

    fn foo<O: Ordering>(_: O) {}

If we don't have the ordering module public and instead re-export from
atomic, you could also write:

    fn foo<Ordering: atomic::Ordering>(_: Ordering) {}

If you want it to be extra clear. What do you think?

---
Cheers,
Benno

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