linux-kernel - Re: [PATCH v3 5/7] rust: percpu: Support non-zeroable types for DynamicPerCpu

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Message-ID: <aLoIm94aP6Er0Gn8@yury>
Date: Thu, 4 Sep 2025 17:46:03 -0400
From: Yury Norov <yury.norov@...il.com>
To: Mitchell Levy <levymitchell0@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Benno Lossin <lossin@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Tyler Hicks <code@...icks.com>, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 5/7] rust: percpu: Support non-zeroable types for
 DynamicPerCpu

> > 
> >         for_each_possible_cpu(cpu) {
> >                 let remote_ptr = unsafe { ptr.get_remote_ptr(cpu) };
> >                 unsafe { (*remote_ptr).write(val.clone()); }
> >                 let arc = Arc::new(alloc, flags).ok()?;
> >                 Some(Self { alloc: arc })
> >         }
> > 
> > Is it possible to do the above in rust?
> 
> Ah, I see.
> 
> The syntax would be slightly different, probably something like
> 
>         use cpu::for_each_possible_cpu;
> 
>         for_each_possible_cpu(|&cpu| {
>                 let remote_ptr = unsafe { ptr.get_remote_ptr(cpu) };
>                 // ...
>         })
> 
> it *might* also be possible to use a macro and dispense with the need for
> a closure, though I'm not familiar enough with proc macros to say for
> sure. That would probably look like
> 
>         for_each_possible_cpu!(cpu) {
>                 let remote_ptr = unsafe { ptr.get_remote_ptr(cpu) };
>                 // ...
>         }
> 
> though personally I think the first one is better (simpler
> implementation without too much syntactic overhead, especially since
> closures are already used some within R4L).

Sure, #1 is OK if you prefer it.