[PATCH 09/13] rust: list: Use AtomicFlag in AtomicTracker

[Boqun Feng]

From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxx>

Make AtomicTracker use AtomicFlag instead of Atomic<bool> to avoid
slow byte-sized RMWs on architectures that don't support them.

Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxx>
Signed-off-by: Boqun Feng <boqun@xxxxxxxxxx>
Link: https://patch.msgid.link/20260129122622.3896144-3-tomo@xxxxxxxxxxxx
---
 rust/kernel/list/arc.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/rust/kernel/list/arc.rs b/rust/kernel/list/arc.rs
index 2282f33913ee..5e84f500a3fe 100644
--- a/rust/kernel/list/arc.rs
+++ b/rust/kernel/list/arc.rs
@@ -6,7 +6,7 @@
 
 use crate::alloc::{AllocError, Flags};
 use crate::prelude::*;
-use crate::sync::atomic::{ordering, Atomic};
+use crate::sync::atomic::{ordering, AtomicFlag};
 use crate::sync::{Arc, ArcBorrow, UniqueArc};
 use core::marker::PhantomPinned;
 use core::ops::Deref;
@@ -469,7 +469,7 @@ impl<T, U, const ID: u64> core::ops::DispatchFromDyn<ListArc<U, ID>> for ListArc
 /// If the boolean is `false`, then there is no [`ListArc`] for this value.
 #[repr(transparent)]
 pub struct AtomicTracker<const ID: u64 = 0> {
-    inner: Atomic<bool>,
+    inner: AtomicFlag,
     // This value needs to be pinned to justify the INVARIANT: comment in `AtomicTracker::new`.
     _pin: PhantomPinned,
 }
@@ -480,12 +480,12 @@ pub fn new() -> impl PinInit<Self> {
         // INVARIANT: Pin-init initializers can't be used on an existing `Arc`, so this value will
         // not be constructed in an `Arc` that already has a `ListArc`.
         Self {
-            inner: Atomic::new(false),
+            inner: AtomicFlag::new(false),
             _pin: PhantomPinned,
         }
     }
 
-    fn project_inner(self: Pin<&mut Self>) -> &mut Atomic<bool> {
+    fn project_inner(self: Pin<&mut Self>) -> &mut AtomicFlag {
         // SAFETY: The `inner` field is not structurally pinned, so we may obtain a mutable
         // reference to it even if we only have a pinned reference to `self`.
         unsafe { &mut Pin::into_inner_unchecked(self).inner }
-- 
2.50.1 (Apple Git-155)