Re: C aggregate passing (Rust kernel policy)

[Ralf Jung]

Hi,

On 27.02.25 20:15, Linus Torvalds wrote:
> On Thu, 27 Feb 2025 at 10:33, Ralf Jung <post@xxxxxxxx> wrote:
> > The way you do global flags in Rust is like this:
>
> Note that I was really talking mainly about the unsafe cases, an din
> particular when interfacing with C code.

When Rust code and C code share memory that is concurrently accessed, all 
accesses to that from the Rust side must be explicitly marked as atomic. A 
pointer to such a memory should look like `&AtomicBool` in Rust, not `*mut 
bool`. To my knowledge, the kernel already has appropriate APIs for that. That 
will then ensure things behave like the AtomicBool example.

Kind regards,
Ralf

> Also, honestly:
>
> > FLAG.store(true, Ordering::SeqCst); // or release/acquire/relaxed
>
> I suspect in reality it would be hidden as accessor functions, or
> people just continue to write things in C.
>
> Yes, I know all about the C++ memory ordering. It's not only a
> standards mess, it's all very illegible code too.
>
>               Linus