[PATCH v2] rust: sync: optimize rust symbol generation for CondVar

Kunwu Chan
2025-03-24T06:19:20Z

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>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>

---
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