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From: Andreas Hindborg <a.hindborg@kernel.org>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Will Deacon <will@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
 Boqun Feng <boqun.feng@gmail.com>, Mark Rutland <mark.rutland@arm.com>,
 Gary Guo <gary@garyguo.net>, Miguel Ojeda <ojeda@kernel.org>, =?utf-8?Q?B?=
 =?utf-8?Q?j=C3=B6rn?= Roy
 Baron <bjorn3_gh@protonmail.com>, Benno Lossin <lossin@kernel.org>, Alice
 Ryhl <aliceryhl@google.com>, Trevor Gross <tmgross@umich.edu>, Danilo
 Krummrich <dakr@kernel.org>, linux-kernel@vger.kernel.org,
 rust-for-linux@vger.kernel.org
Subject: Re: [PATCH v2 1/2] rust: atomic: add fetch_sub
In-Reply-To: <CANiq72=JXKLwSDtS2TPr4zy=nEjKOPTKcG+Yg0U4u+GU07WwdA@mail.gmail.com>
References: <20260219-atomic-sub-v2-0-8bd99cadf26d@kernel.org>
 <20260219-atomic-sub-v2-1-8bd99cadf26d@kernel.org>
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 <CANiq72=JXKLwSDtS2TPr4zy=nEjKOPTKcG+Yg0U4u+GU07WwdA@mail.gmail.com>
Date: Thu, 19 Feb 2026 14:34:21 +0100
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"Miguel Ojeda" <miguel.ojeda.sandonis@gmail.com> writes:

> On Thu, Feb 19, 2026 at 1:20=E2=80=AFPM Andreas Hindborg <a.hindborg@kern=
el.org> wrote:
>>
>> +        fn fetch_sub[acquire, release, relaxed](a: &AtomicRepr<Self>, v=
: Self::Delta) -> Self {
>> +            // SAFETY: `a.as_ptr()` is valid and properly aligned.
>> +            unsafe { bindings::#call(v, a.as_ptr().cast()) }
>> +        }
>
> [ I see `fetch_add` does the same, so it is fine here in this patch
> for consistency, but I thought I would leave a note here anyway... ]
>
> The safety comment, as written, could be read as just saying something
> it is true without justifying it. Something like:
>
>     `a.as_ptr()` guarantees the returned pointer is valid and properly al=
igned.

I'll respin and fix this, for `fetch_add` as well. I can take the
spurious newline you mentioned on same occasion.


Best regards,
Andreas Hindborg