From: FUJITA Tomonori <fujita.tomonori@gmail.com>
Date: Tue, 3 Mar 2026 20:16:57 +0000 (-0800)
Subject: rust: list: Use AtomicFlag in AtomicTracker
X-Git-Tag: v7.1-rc1~199^2~22
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=282866207020b15c2afc4d43b1ca0c5d96c9032d;p=thirdparty%2Fkernel%2Flinux.git

rust: list: Use AtomicFlag in AtomicTracker

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

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260129122622.3896144-3-tomo@aliasing.net
Link: https://patch.msgid.link/20260303201701.12204-10-boqun@kernel.org
---

diff --git a/rust/kernel/list/arc.rs b/rust/kernel/list/arc.rs
index 2282f33913ee9..5e84f500a3fee 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 @@ where
 /// 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 @@ impl<const ID: u64> AtomicTracker<ID> {
         // 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 }