[PATCH] rust: sync: optimize rust symbol generation for CondVar

Kunwu Chan
2025-03-17T08:14:51Z

From: Kunwu Chan <kunwu.chan@hotmail.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@google.com>
Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>
---
rust/kernel/sync/condvar.rs | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index 7df565038d7d..a826896ba3f0 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -181,6 +181,7 @@ pub fn wait_interruptible_timeout<T: ?Sized, B: Backend>(
}

/// Calls the kernel function to notify the appropriate number of threads.
+ #[inline]
fn notify(&self, count: c_int) {
// SAFETY: `wait_queue_head` points to valid memory.
unsafe {
@@ -198,6 +199,7 @@ 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) };
@@ -207,6 +209,7 @@ 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);
}
@@ -215,6 +218,7 @@ 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