Messages in this thread Patch in this message | | | Date | Tue, 23 May 2023 14:44:17 +0000 | Subject | [PATCH v2 3/4] rust: specify when `ARef` is thread safe | From | Alice Ryhl <> |
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An `ARef` behaves just like the `Arc` when it comes to thread safety, so we can reuse the thread safety comments from `Arc` here.
This is necessary because without this change, the Rust compiler will assume that things are not thread safe even though they are.
Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> --- rust/kernel/types.rs | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index 29db59d6119a..1e5380b16ed5 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -321,6 +321,19 @@ pub struct ARef<T: AlwaysRefCounted> { _p: PhantomData<T>, } +// SAFETY: It is safe to send `ARef<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 `ARef<T>` may ultimately access `T` using a +// mutable reference, for example, when the reference count reaches zero and `T` is dropped. +unsafe impl<T: AlwaysRefCounted + Sync + Send> Send for ARef<T> {} + +// SAFETY: It is safe to send `&ARef<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 a `&ARef<T>` may clone it and get an +// `ARef<T>` on that thread, so the thread may ultimately access `T` using a mutable reference, for +// example, when the reference count reaches zero and `T` is dropped. +unsafe impl<T: AlwaysRefCounted + Sync + Send> Sync for ARef<T> {} + impl<T: AlwaysRefCounted> ARef<T> { /// Creates a new instance of [`ARef`]. /// -- 2.40.1.698.g37aff9b760-goog
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