linux-kernel - Re: [PATCH v2] rust: sync: optimize rust symbol generation for CondVar

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Message-ID: <aAem8H4WhLBTf3xv@Mac.home>
Date: Tue, 22 Apr 2025 07:25:52 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Kunwu Chan <kunwu.chan@...ux.dev>
Cc: ojeda@...nel.org, alex.gaynor@...il.com, gary@...yguo.net,
	bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
	a.hindborg@...nel.org, aliceryhl@...gle.com, tmgross@...ch.edu,
	dakr@...nel.org, nathan@...nel.org, nick.desaulniers+lkml@...il.com,
	morbo@...gle.com, justinstitt@...gle.com,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev, Kunwu Chan <kunwu.chan@...mail.com>,
	Grace Deng <Grace.Deng006@...il.com>
Subject: Re: [PATCH v2] rust: sync: optimize rust symbol generation for
 CondVar

On Mon, Mar 24, 2025 at 02:18:34PM +0800, Kunwu Chan wrote:
> From: Kunwu Chan <kunwu.chan@...mail.com>
> 
> When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
> with ARCH=arm64, the following symbols are generated:
> 
> $nm vmlinux | grep ' _R'.*CondVar | rustfilt
> ... T <kernel::sync::condvar::CondVar>::notify_all
> ... T <kernel::sync::condvar::CondVar>::notify_one
> ... T <kernel::sync::condvar::CondVar>::notify_sync
> ... T <kernel::sync::condvar::CondVar>::new::{closure#0}::{closure#0}::panic_cold_explicit
> ... T <kernel::sync::condvar::CondVar>::new::{closure#0}::{closure#0}::panic_cold_explicit
> ... T <kernel::sync::poll::PollCondVar>::new::{closure#0}::{closure#0}::panic_cold_explicit
> ... T <kernel::sync::poll::PollCondVar as core::ops::drop::Drop>::drop
> 
> These notify_* symbols are trivial wrappers around the C functions
> __wake_up and __wake_up_sync. It doesn't make sense to go through
> a trivial wrapper for these functions, so mark them inline.
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
> Co-developed-by: Grace Deng <Grace.Deng006@...il.com>
> Signed-off-by: Grace Deng <Grace.Deng006@...il.com>
> Signed-off-by: Kunwu Chan <kunwu.chan@...mail.com>
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> 

I'm taking this via tip with the version as it is (i.e. no #[inline] for
notify()), but will reorder the tags. Thanks!

Regards,
Boqun

> ---
> Changes in v2:
> - Remove '#[inline]' for notify()
> - Reword commit msg
> - v1 link: https://lore.kernel.org/rust-for-linux/01c67d96-6477-4851-81ae-0cbee3b9e893@linux.dev
> ---
>  rust/kernel/sync/condvar.rs | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
> index caebf03f553b..c6ec64295c9f 100644
> --- a/rust/kernel/sync/condvar.rs
> +++ b/rust/kernel/sync/condvar.rs
> @@ -216,6 +216,7 @@ fn notify(&self, count: c_int) {
>      /// This method behaves like `notify_one`, except that it hints to the scheduler that the
>      /// current thread is about to go to sleep, so it should schedule the target thread on the same
>      /// CPU.
> +    #[inline]
>      pub fn notify_sync(&self) {
>          // SAFETY: `wait_queue_head` points to valid memory.
>          unsafe { bindings::__wake_up_sync(self.wait_queue_head.get(), TASK_NORMAL) };
> @@ -225,6 +226,7 @@ pub fn notify_sync(&self) {
>      ///
>      /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
>      /// completely (as opposed to automatically waking up the next waiter).
> +    #[inline]
>      pub fn notify_one(&self) {
>          self.notify(1);
>      }
> @@ -233,6 +235,7 @@ pub fn notify_one(&self) {
>      ///
>      /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
>      /// completely (as opposed to automatically waking up the next waiter).
> +    #[inline]
>      pub fn notify_all(&self) {
>          self.notify(0);
>      }
> -- 
> 2.43.0
> 
>