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rust: sync: add support for dispatching on Arc and ArcBorrow.

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Trait objects (`dyn T`) require trait `T` to be "object safe". One of
the requirements for "object safety" is that the receiver have one of
the allowed types. This commit adds `Arc<T>` and `ArcBorrow<'_, T>` to
the list of allowed types.

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Wedson Almeida Filho 2022-12-28 06:03:46 +00:00 committed by Miguel Ojeda
parent 70e42ebbf6
commit 0748424aba
2 changed files with 19 additions and 2 deletions
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1
rust/kernel/lib.rs
View file

@ -15,6 +15,7 @@
#![feature(allocator_api)]
#![feature(coerce_unsized)]
#![feature(core_ffi_c)]
#![feature(dispatch_from_dyn)]
#![feature(receiver_trait)]
#![feature(unsize)]

20
rust/kernel/sync/arc.rs
View file

@ -92,9 +92,15 @@
/// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
///
/// ```
/// use kernel::sync::Arc;
/// use kernel::sync::{Arc, ArcBorrow};
///
/// trait MyTrait {}
/// trait MyTrait {
/// // Trait has a function whose `self` type is `Arc<Self>`.
/// fn example1(self: Arc<Self>) {}
///
/// // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`.
/// fn example2(self: ArcBorrow<'_, Self>) {}
/// }
///
/// struct Example;
/// impl MyTrait for Example {}
@ -123,6 +129,9 @@ impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
// dynamically-sized type (DST) `U`.
impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> 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
@ -297,6 +306,13 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
// This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
// `ArcBorrow<U>`.
impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
for ArcBorrow<'_, T>
{
}
impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
fn clone(&self) -> Self {
*self