Messages in this thread Patch in this message | | | Date | Wed, 17 May 2023 09:59:04 +0000 | Subject | [PATCH v1 1/2] 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> --- rust/kernel/types.rs | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index 29db59d6119a..9c8d94c04deb 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -321,6 +321,17 @@ 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` directly, 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` for the +// same reason as above. `T` needs to be `Send` as well because a thread can clone an `&ARef<T>` +// into an `ARef<T>`, which may lead to `T` being accessed by the same reasoning as above. +unsafe impl<T: AlwaysRefCounted + Sync + Send> Sync for ARef<T> {} + impl<T: AlwaysRefCounted> ARef<T> { /// Creates a new instance of [`ARef`]. /// base-commit: ac9a78681b921877518763ba0e89202254349d1b -- 2.40.1.606.ga4b1b128d6-goog
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