linux-kernel - Re: [PATCH] rust: kernel: cpu: mark `CpuId::current()` inline

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Message-ID: <aJlGVfdwVXp6Cmcw@Mac.home>
Date: Sun, 10 Aug 2025 18:24:37 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Ritvik Gupta <ritvikfoss@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, skhan@...uxfoundation.org,
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: Re: [PATCH] rust: kernel: cpu: mark `CpuId::current()` inline

On Mon, Aug 11, 2025 at 06:49:58AM +0530, Ritvik Gupta wrote:
> When building the kernel using llvm-20.1.7-rust-1.89.0-x86_64,
> this symbol is generated:
> 
> $ llvm-nm --demangle vmlinux | grep CpuId
> ffffffff84c77450 T <kernel::cpu::CpuId>::current
> 
> However, this Rust symbol is a trivial wrapper around
> `raw_smp_processor_id` function. It doesn't make sense
> to go through a trivial wrapper for such functions,
> so mark it inline.
> 
> After applying this patch, the above command will produce no output.
> 
> Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Signed-off-by: Ritvik Gupta <ritvikfoss@...il.com>

Reviewed-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> ---
>  rust/kernel/cpu.rs | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs
> index 5de730c8d817..cb6c0338ef5a 100644
> --- a/rust/kernel/cpu.rs
> +++ b/rust/kernel/cpu.rs
> @@ -109,6 +109,7 @@ pub fn as_u32(&self) -> u32 {
>      /// unexpectedly due to preemption or CPU migration. It should only be
>      /// used when the context ensures that the task remains on the same CPU
>      /// or the users could use a stale (yet valid) CPU ID.
> +    #[inline]
>      pub fn current() -> Self {
>          // SAFETY: raw_smp_processor_id() always returns a valid CPU ID.
>          unsafe { Self::from_u32_unchecked(bindings::raw_smp_processor_id()) }
> 
> base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
> -- 
> 2.50.1
>