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From: Andreas Hindborg <a.hindborg@kernel.org>
To: "Oliver Mangold" <oliver.mangold@pm.me>
Cc: "Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Asahi Lina" <lina@asahilina.net>,
	rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10 3/5] rust: Add missing SAFETY documentation for ARef example
Date: Fri, 02 May 2025 12:41:01 +0200	[thread overview]
Message-ID: <87ikmjz45e.fsf@kernel.org> (raw)
In-Reply-To: <20250502-unique-ref-v10-3-25de64c0307f@pm.me> (Oliver Mangold's message of "Fri, 02 May 2025 09:02:46 +0000")

"Oliver Mangold" <oliver.mangold@pm.me> writes:

> SAFETY comment in rustdoc example was just 'TODO'. Fixed.
>
> Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
> ---
>  rust/kernel/types.rs | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
> index d7fa8934c545f46a646ca900ab8957a04b0ad34d..33d2b4e4a87b991c6d934f4e8d2c6c71a15b1bcb 100644
> --- a/rust/kernel/types.rs
> +++ b/rust/kernel/types.rs
> @@ -498,7 +498,9 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
>      ///
>      /// struct Empty {}
>      ///
> -    /// # // SAFETY: TODO.
> +    /// // SAFETY: The `RefCounted` implementation for `Empty` does not count references
> +    /// // and never frees the underlying object. Thus we can act as having a
> +    /// // refcount on the object that we pass to the newly created `ARef`.
>      /// unsafe impl RefCounted for Empty {
>      ///     fn inc_ref(&self) {}
>      ///     unsafe fn dec_ref(_obj: NonNull<Self>) {}
> @@ -506,7 +508,7 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
>      ///
>      /// let mut data = Empty {};
>      /// let ptr = NonNull::<Empty>::new(&mut data).unwrap();
> -    /// # // SAFETY: TODO.
> +    /// // SAFETY: We keep `data` around longer than the `ARef`.

I still think this applies:

>> How about:
>> 
>>   The `RefCounted` implementation for `Empty` does not count references
>>   and never frees the underlying object. Thus we can act as having a
>>   refcount on the object that we pass to the newly created `ARef`.
>> 

>      /// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
>      /// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
>      ///


Best regards,
Andreas Hindborg



  reply	other threads:[~2025-05-02 10:41 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-02  9:02 [PATCH v10 0/5] New trait OwnableRefCounted for ARef<->Owned conversion Oliver Mangold
2025-05-02  9:02 ` [PATCH v10 1/5] rust: types: Add Ownable/Owned types Oliver Mangold
2025-05-02  9:57   ` Andreas Hindborg
2025-06-16 11:43     ` Oliver Mangold
2025-06-17 11:42       ` Andreas Hindborg
2025-05-02 11:29   ` Alice Ryhl
2025-05-06 11:20     ` Andreas Hindborg
2025-05-07  6:20       ` Alice Ryhl
2025-05-08 12:24   ` Andreas Hindborg
2025-05-14  9:32   ` Benno Lossin
2025-06-17  9:58     ` Oliver Mangold
2025-06-18 21:22       ` Benno Lossin
2025-06-20  7:01         ` Oliver Mangold
2025-06-20  8:09           ` Benno Lossin
2025-06-18  9:34     ` Oliver Mangold
2025-06-18 21:19       ` Benno Lossin
2025-06-19  9:33         ` Andreas Hindborg
2025-06-19 12:18           ` Benno Lossin
2025-05-02  9:02 ` [PATCH v10 2/5] rust: Rename AlwaysRefCounted to RefCounted Oliver Mangold
2025-05-02 10:10   ` Andreas Hindborg
2025-05-02 11:32   ` Alice Ryhl
2025-06-16 11:56     ` Oliver Mangold
2025-06-16 12:13       ` Alice Ryhl
2025-05-02  9:02 ` [PATCH v10 3/5] rust: Add missing SAFETY documentation for ARef example Oliver Mangold
2025-05-02 10:41   ` Andreas Hindborg [this message]
2025-05-02 11:12     ` Oliver Mangold
2025-05-02 12:01       ` Andreas Hindborg
2025-05-02  9:02 ` [PATCH v10 4/5] rust: kbuild: provide `RUSTC_HAS_DO_NOT_RECOMMEND` symbol Oliver Mangold
2025-05-02  9:03 ` [PATCH v10 5/5] rust: Add OwnableRefCounted and SimpleOwnableRefCounted Oliver Mangold
2025-05-02 11:43   ` Alice Ryhl
2025-05-06 11:42     ` Oliver Mangold
2025-05-07  6:19       ` Alice Ryhl
2025-06-13 13:10 ` [PATCH v10 0/5] New trait OwnableRefCounted for ARef<->Owned conversion Andreas Hindborg
2025-06-13 13:27   ` Oliver Mangold

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