rust: kernel: cpu: mark `CpuId::current()` inline

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

Posted by Ritvik Gupta 1 month, 3 weeks ago

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@google.com>
Link: https://github.com/Rust-for-Linux/linux/issues/1145
Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>
---
 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

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

Posted by Miguel Ojeda 2 weeks, 6 days ago

On Mon, Aug 11, 2025 at 3:19 AM Ritvik Gupta <ritvikfoss@gmail.com> 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@google.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

Applied to `rust-next` -- thanks everyone!

Cheers,
Miguel

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

Posted by Miguel Ojeda 3 weeks, 6 days ago

On Mon, Aug 11, 2025 at 3:19 AM Ritvik Gupta <ritvikfoss@gmail.com> 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@google.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

If no one is planning to pick this one, I will -- thanks!

Cheers,
Miguel

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

Posted by Alice Ryhl 1 month, 3 weeks ago

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@google.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

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

Posted by Boqun Feng 1 month, 3 weeks ago

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@google.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

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