Re: [PATCH v2 1/2] rust: Add cpu_relax() helper

[ChaosEsque Team]

Futa Daniel?
Comon.

On Tue, Aug 19, 2025 at 2:35 PM Daniel Almeida
<daniel.almeida@xxxxxxxxxxxxx> wrote:
>
>
>
> > On 17 Aug 2025, at 01:47, FUJITA Tomonori <fujita.tomonori@xxxxxxxxx> wrote:
> >
> > Add cpu_relax() helper in preparation for supporting
> > read_poll_timeout().
> >
> > Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> > Reviewed-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxx>
> > ---
> > rust/helpers/helpers.c   |  1 +
> > rust/helpers/processor.c |  8 ++++++++
> > rust/kernel/lib.rs       |  1 +
> > rust/kernel/processor.rs | 14 ++++++++++++++
> > 4 files changed, 24 insertions(+)
> > create mode 100644 rust/helpers/processor.c
> > create mode 100644 rust/kernel/processor.rs
> >
> > diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> > index 7cf7fe95e41d..04598665e7c8 100644
> > --- a/rust/helpers/helpers.c
> > +++ b/rust/helpers/helpers.c
> > @@ -34,6 +34,7 @@
> > #include "pid_namespace.c"
> > #include "platform.c"
> > #include "poll.c"
> > +#include "processor.c"
> > #include "property.c"
> > #include "rbtree.c"
> > #include "rcu.c"
> > diff --git a/rust/helpers/processor.c b/rust/helpers/processor.c
> > new file mode 100644
> > index 000000000000..d41355e14d6e
> > --- /dev/null
> > +++ b/rust/helpers/processor.c
> > @@ -0,0 +1,8 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <linux/processor.h>
> > +
> > +void rust_helper_cpu_relax(void)
> > +{
> > + cpu_relax();
> > +}
> > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> > index ed53169e795c..c098c47c1817 100644
> > --- a/rust/kernel/lib.rs
> > +++ b/rust/kernel/lib.rs
> > @@ -110,6 +110,7 @@
> > pub mod platform;
> > pub mod prelude;
> > pub mod print;
> > +pub mod processor;
> > pub mod rbtree;
> > pub mod regulator;
> > pub mod revocable;
> > diff --git a/rust/kernel/processor.rs b/rust/kernel/processor.rs
> > new file mode 100644
> > index 000000000000..85b49b3614dd
> > --- /dev/null
> > +++ b/rust/kernel/processor.rs
> > @@ -0,0 +1,14 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +//! Processor related primitives.
> > +//!
> > +//! C header: [`include/linux/processor.h`](srctree/include/linux/processor.h)
> > +
> > +/// Lower CPU power consumption or yield to a hyperthreaded twin processor.
> > +///
> > +/// It also happens to serve as a compiler barrier.
> > +#[inline]
> > +pub fn cpu_relax() {
> > +    // SAFETY: Always safe to call.
> > +    unsafe { bindings::cpu_relax() }
> > +}
> > --
> > 2.43.0
> >
> >
>
> Reviewed-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>