linux-kernel - Re: [PATCH v8 03/14] rust: sync: add `Arc::as

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Message-ID: <59064411-ae6c-4adb-8b3a-186f8004c2a0@proton.me>
Date: Thu, 20 Feb 2025 23:18:36 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Andreas Hindborg <a.hindborg@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Danilo Krummrich <dakr@...nel.org>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Lyude Paul <lyude@...hat.com>, Guangbo Cui <2407018371@...com>, Dirk Behme <dirk.behme@...il.com>, Daniel Almeida <daniel.almeida@...labora.com>, Tamir Duberstein <tamird@...il.com>, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 03/14] rust: sync: add `Arc::as_ptr`

On 18.02.25 14:27, Andreas Hindborg wrote:
> Add a method to get a pointer to the data contained in an `Arc`.
> 
> Reviewed-by: Lyude Paul <lyude@...hat.com>
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> ---

Reviewed-by: Benno Lossin <benno.lossin@...ton.me>

---
Cheers,
Benno

> 
> This is a dependency for:
> 
> rust: hrtimer: implement `HrTimerPointer` for `Arc`
> ---
>  rust/kernel/sync/arc.rs | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 3cefda7a43725..1dfa75714f9d6 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -246,6 +246,15 @@ pub fn into_raw(self) -> *const T {
>          unsafe { core::ptr::addr_of!((*ptr).data) }
>      }
> 
> +    /// Return a raw pointer to the data in this arc.
> +    pub fn as_ptr(this: &Self) -> *const T {
> +        let ptr = this.ptr.as_ptr();
> +
> +        // SAFETY: As `ptr` points to a valid allocation of type `ArcInner`,
> +        // field projection to `data`is within bounds of the allocation.
> +        unsafe { core::ptr::addr_of!((*ptr).data) }
> +    }
> +
>      /// Recreates an [`Arc`] instance previously deconstructed via [`Arc::into_raw`].
>      ///
>      /// # Safety
> @@ -539,11 +548,11 @@ unsafe fn new(inner: NonNull<ArcInner<T>>) -> Self {
>      }
> 
>      /// Creates an [`ArcBorrow`] to an [`Arc`] that has previously been deconstructed with
> -    /// [`Arc::into_raw`].
> +    /// [`Arc::into_raw`] or [`Arc::as_ptr`].
>      ///
>      /// # Safety
>      ///
> -    /// * The provided pointer must originate from a call to [`Arc::into_raw`].
> +    /// * The provided pointer must originate from a call to [`Arc::into_raw`] or [`Arc::as_ptr`].
>      /// * For the duration of the lifetime annotated on this `ArcBorrow`, the reference count must
>      ///   not hit zero.
>      /// * For the duration of the lifetime annotated on this `ArcBorrow`, there must not be a
> 
> --
> 2.47.0
> 
>