linux-kernel - [PATCH v2] rust: sync: optimize Rust symbol generation for PollCondVar

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Message-ID: <20250317025205.2366518-1-kunwu.chan@linux.dev>
Date: Mon, 17 Mar 2025 10:52:05 +0800
From: Kunwu Chan <kunwu.chan@...ux.dev>
To: ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...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
Cc: 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: [PATCH v2] rust: sync: optimize Rust symbol generation for PollCondVar

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'.*PollCondVar  | rustfilt
... T <kernel::sync::poll::PollCondVar>::new::{closure#0}::{closure#0}::panic_cold_explicit
... T <kernel::sync::poll::PollCondVar as kernel::init::PinnedDrop>::drop
... T <kernel::sync::poll::PollCondVar as core::ops::drop::Drop>::drop

This Rust symbol
(<kernel::sync::poll::PollCondVar as kernel::init::PinnedDrop>::drop)
is trivial wrappers around the C functions __wake_up_pollfree
and synchronize_rcu. It doesn't make sense to go through a trivial
wrapper for its functions,so mark it 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>

---
Changes in v2:
 - Add link and Suggested-by
 - Reword commit msg
---
 rust/kernel/sync/poll.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rust/kernel/sync/poll.rs b/rust/kernel/sync/poll.rs
index d5f17153b424..a4f92c545fec 100644
--- a/rust/kernel/sync/poll.rs
+++ b/rust/kernel/sync/poll.rs
@@ -107,6 +107,7 @@ fn deref(&self) -> &CondVar {
 
 #[pinned_drop]
 impl PinnedDrop for PollCondVar {
+    #[inline]
     fn drop(self: Pin<&mut Self>) {
         // Clear anything registered using `register_wait`.
         //
-- 
2.43.0