Re: [PATCH v7 6/9] rust: sync: atomic: Add the framework of arithmetic operations

On Wed Jul 16, 2025 at 5:48 PM CEST, Boqun Feng wrote:

On Wed, Jul 16, 2025 at 05:36:05PM +0200, Benno Lossin wrote:
[..]

quoted

quoted

I have a better solution:

in ops.rs

    pub struct AtomicRepr<T: AtomicImpl>(UnsafeCell<T>)

    impl AtomicArithmeticOps for i32 {
        // a *safe* function
        fn atomic_add(a: &AtomicRepr, v: i32) {
	    ...
	}
    }

in generic.rs

    pub struct Atomic<T>(AtoimcRepr<T::Repr>);

    impl<T: AtomicAdd> Atomic<T> {
        fn add(&self, v: .., ...) {
	    T::Repr::atomic_add(&self.0, ...);
	}
    }

see:

	https://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git/log/?h=rust-atomic-impl

Hmm what does the additional indirection give you?

What additional indirection you mean? You cannot make atomic_add() safe
with only `UnsafeCell<T::Repr>`.

What is the advantage of making it safe? It just moves the safety
comments into `ops.rs` which makes it harder to read due to the macros.

---
Cheers,
Benno