Commit 28286620 authored by FUJITA Tomonori's avatar FUJITA Tomonori Committed by Peter Zijlstra
Browse files

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: default avatarFUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: default avatarBoqun Feng <boqun@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarGary 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
parent ec6fc66a

rust/kernel/list/arc.rs

+4 −4
Original line number Diff line number Diff line
@@ -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 }