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rust: revocable: Use LKMM atomics instead of Rust atomics

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Kernel code should use LKMM atomics. The existing code is `AtomicBool`
with the need to use `xchg`, so convert it to `AtomicFlag`.

Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun@kernel.org>
Link: https://patch.msgid.link/20260716145536.3681630-1-gary@kernel.org
This commit is contained in:
Gary Guo
2026-07-16 15:55:35 +01:00
committed by Boqun Feng
parent 72856afd33
commit 3f90c16d41
1 changed files with 13 additions and 8 deletions
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21
rust/kernel/revocable.rs
View File

@@ -9,14 +9,19 @@
use crate::{
prelude::*,
sync::rcu,
sync::{
atomic::{
AtomicFlag,
Relaxed, //
},
rcu, //
},
types::Opaque, //
};
use core::{
marker::PhantomData,
ops::Deref,
ptr::drop_in_place,
sync::atomic::{AtomicBool, Ordering},
ptr::drop_in_place, //
};
/// An object that can become inaccessible at runtime.
@@ -69,7 +74,7 @@
/// ```
#[pin_data(PinnedDrop)]
pub struct Revocable<T> {
is_available: AtomicBool,
is_available: AtomicFlag,
#[pin]
data: Opaque<T>,
}
@@ -88,7 +93,7 @@ impl<T> Revocable<T> {
/// Creates a new revocable instance of the given data.
pub fn new<E>(data: impl PinInit<T, E>) -> impl PinInit<Self, E> {
try_pin_init!(Self {
is_available: AtomicBool::new(true),
is_available: AtomicFlag::new(true),
data <- Opaque::pin_init(data),
}? E)
}
@@ -102,7 +107,7 @@ pub fn new<E>(data: impl PinInit<T, E>) -> impl PinInit<Self, E> {
/// because another CPU may be waiting to complete the revocation of this object.
pub fn try_access(&self) -> Option<RevocableGuard<'_, T>> {
let guard = rcu::read_lock();
if self.is_available.load(Ordering::Relaxed) {
if self.is_available.load(Relaxed) {
// Since `self.is_available` is true, data is initialised and has to remain valid
// because the RCU read side lock prevents it from being dropped.
Some(RevocableGuard::new(self.data.get(), guard))
@@ -120,7 +125,7 @@ pub fn try_access(&self) -> Option<RevocableGuard<'_, T>> {
/// allowed to sleep because another CPU may be waiting to complete the revocation of this
/// object.
pub fn try_access_with_guard<'a>(&'a self, _guard: &'a rcu::Guard) -> Option<&'a T> {
if self.is_available.load(Ordering::Relaxed) {
if self.is_available.load(Relaxed) {
// SAFETY: Since `self.is_available` is true, data is initialised and has to remain
// valid because the RCU read side lock prevents it from being dropped.
Some(unsafe { &*self.data.get() })
@@ -161,7 +166,7 @@ pub unsafe fn access(&self) -> &T {
///
/// Callers must ensure that there are no more concurrent users of the revocable object.
unsafe fn revoke_internal<const SYNC: bool>(&self) -> bool {
let revoke = self.is_available.swap(false, Ordering::Relaxed);
let revoke = self.is_available.xchg(false, Relaxed);
if revoke {
if SYNC {