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SubjectRe: [PATCH 2/7] rust: sync: allow type of `self` to be `Arc<T>` or variants
On Wed, 28 Dec 2022 06:03:41 +0000
Wedson Almeida Filho <wedsonaf@gmail.com> wrote:

> This allows associated functions whose `self` argument has `Arc<T>` or
> variants as their type. This, in turn, allows callers to use the dot
> syntax to make calls.
>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
> rust/kernel/lib.rs | 1 +
> rust/kernel/sync/arc.rs | 28 ++++++++++++++++++++++++++++
> 2 files changed, 29 insertions(+)
>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index ace064a3702a..1a10f7c0ddd9 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -14,6 +14,7 @@
> #![no_std]
> #![feature(allocator_api)]
> #![feature(core_ffi_c)]
> +#![feature(receiver_trait)]
>
> // Ensure conditional compilation based on the kernel configuration works;
> // otherwise we may silently break things like initcall handling.
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 22290eb5ab9b..e2eb0e67d483 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -57,6 +57,31 @@ use core::{marker::PhantomData, ops::Deref, ptr::NonNull};
> ///
> /// // The refcount drops to zero when `cloned` goes out of scope, and the memory is freed.
> /// ```
> +///
> +/// Using `Arc<T>` as the type of `self`:
> +///
> +/// ```
> +/// use kernel::sync::Arc;
> +///
> +/// struct Example {
> +/// a: u32,
> +/// b: u32,
> +/// }
> +///
> +/// impl Example {
> +/// fn take_over(self: Arc<Self>) {
> +/// // ...
> +/// }
> +///
> +/// fn use_reference(self: &Arc<Self>) {
> +/// // ...
> +/// }
> +/// }
> +///
> +/// let obj = Arc::try_new(Example { a: 10, b: 20 })?;
> +/// obj.use_reference();
> +/// obj.take_over();
> +/// ```
> pub struct Arc<T: ?Sized> {
> ptr: NonNull<ArcInner<T>>,
> _p: PhantomData<ArcInner<T>>,
> @@ -68,6 +93,9 @@ struct ArcInner<T: ?Sized> {
> data: T,
> }
>
> +// This is to allow [`Arc`] (and variants) to be used as the type of `self`.
> +impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
> +
> // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
> // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
> // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for

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