From: Gary Guo gary@garyguo.net

[ Upstream commit c95bbb59a9b22f9b838b15d28319185c1c884329 ]

The term "receiver" means that a type can be used as the type of `self`, and thus enables method call syntax `foo.bar()` instead of `Foo::bar(foo)`. Stable Rust as of today (1.81) enables a limited selection of types (primitives and types in std, e.g. `Box` and `Arc`) to be used as receivers, while custom types cannot.

We want the kernel `Arc` type to have the same functionality as the Rust std `Arc`, so we use the `Receiver` trait (gated behind `receiver_trait` unstable feature) to gain the functionality.

The `arbitrary_self_types` RFC [1] (tracking issue [2]) is accepted and it will allow all types that implement a new `Receiver` trait (different from today's unstable trait) to be used as receivers. This trait will be automatically implemented for all `Deref` types, which include our `Arc` type, so we no longer have to opt-in to be used as receiver. To prepare us for the change, remove the `Receiver` implementation and the associated feature. To still allow `Arc` and others to be used as method receivers, turn on `arbitrary_self_types` feature instead.

This feature gate is introduced in 1.23.0. It used to enable both `Deref` types and raw pointer types to be used as receivers, but the latter is now split into a different feature gate in Rust 1.83 nightly. We do not need receivers on raw pointers so this change would not affect us and usage of `arbitrary_self_types` feature would work for all Rust versions that we support (>=1.78).

Cc: Adrian Taylor ade@hohum.me.uk Link: https://github.com/rust-lang/rfcs/pull/3519 [1] Link: https://github.com/rust-lang/rust/issues/44874 [2] Signed-off-by: Gary Guo gary@garyguo.net Reviewed-by: Benno Lossin benno.lossin@proton.me Reviewed-by: Alice Ryhl aliceryhl@google.com Link: https://lore.kernel.org/r/20240915132734.1653004-1-gary@garyguo.net Signed-off-by: Miguel Ojeda ojeda@kernel.org --- Please consider applying to 6.12.y.

It is meant to support the upcoming Rust 1.84.0 compiler (to be released in a month), since 6.12 LTS is the first stable kernel that supports a minimum Rust version, thus users may use newer compilers. Older LTSs do not need it, for that reason.

rust/kernel/lib.rs | 2 +- rust/kernel/list/arc.rs | 3 --- rust/kernel/sync/arc.rs | 6 ------ scripts/Makefile.build | 2 +- 4 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 032c9089e686..e936254531fd 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -12,10 +12,10 @@ //! do so first instead of bypassing this crate.

#![no_std] +#![feature(arbitrary_self_types)] #![feature(coerce_unsized)] #![feature(dispatch_from_dyn)] #![feature(new_uninit)] -#![feature(receiver_trait)] #![feature(unsize)]

// Ensure conditional compilation based on the kernel configuration works; diff --git a/rust/kernel/list/arc.rs b/rust/kernel/list/arc.rs index d801b9dc6291..3483d8c232c4 100644 --- a/rust/kernel/list/arc.rs +++ b/rust/kernel/list/arc.rs @@ -441,9 +441,6 @@ fn as_ref(&self) -> &Arc<T> { } }

-// This is to allow [`ListArc`] (and variants) to be used as the type of `self`. -impl<T, const ID: u64> core::ops::Receiver for ListArc<T, ID> where T: ListArcSafe<ID> + ?Sized {} - // This is to allow coercion from `ListArc<T>` to `ListArc<U>` if `T` can be converted to the // dynamically-sized type (DST) `U`. impl<T, U, const ID: u64> core::ops::CoerceUnsized<ListArc<U, ID>> for ListArc<T, ID> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index 3021f30fd822..28743a7c74a8 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -171,9 +171,6 @@ unsafe fn container_of(ptr: *const T) -> NonNull<ArcInner<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> {} - // This is to allow coercion from `Arc<T>` to `Arc<U>` if `T` can be converted to the // dynamically-sized type (DST) `U`. impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {} @@ -480,9 +477,6 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> { _p: PhantomData<&'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>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 8f423a1faf50..880785b52c04 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -248,7 +248,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE # Compile Rust sources (.rs) # ---------------------------------------------------------------------------

-rust_allowed_features := new_uninit +rust_allowed_features := arbitrary_self_types,new_uninit

# `--out-dir` is required to avoid temporaries being created by `rustc` in the # current working directory, which may be not accessible in the out-of-tree

base-commit: 61baee2dc5341c936e7fa7b1ca33c5607868de69 -- 2.47.1