Re: [PATCH RFC 3/3] rust: percpu: add a rust per-CPU variable test

[Christoph Lameter (Ampere)]

On Thu, 19 Dec 2024, Mitchell Levy wrote:

> +        let mut native: i64 = 0;
> +        let mut pcpu: PerCpuRef<i64> = unsafe { unsafe_get_per_cpu_ref!(PERCPU, CpuGuard::new()) };

A bit complex.

> +        native += -1;
> +        *pcpu += -1;
> +        assert!(native == *pcpu && native == -1);
> +
> +        native += 1;
> +        *pcpu += 1;
> +        assert!(native == *pcpu && native == 0);
> +

That's pretty straightforward..... But is there no symbolic access to the
per cpu namespace? How would you access the kernel per cpu variables
defined in C?

How do you go about using per cpu atomics like

this_cpu_inc(nr_dentry_unused);