[PATCH v5 07/10] rust: sync: atomic: Add Atomic<u{32,64}>

Boqun Feng
2025-06-18T16:49:49Z

Add generic atomic support for basic unsigned types that have an
`AtomicImpl` with the same size and alignment.

Unit tests are added including Atomic<i32> and Atomic<i64>.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
rust/kernel/sync/atomic.rs | 111 +++++++++++++++++++++++++++++++++++++
1 file changed, 111 insertions(+)

diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
index a01e44eec380..965a3db554d9 100644
--- a/rust/kernel/sync/atomic.rs
+++ b/rust/kernel/sync/atomic.rs
@@ -22,3 +22,114 @@

pub use generic::Atomic;
pub use ordering::{Acquire, Full, Relaxed, Release};
+
+// SAFETY: `u64` and `i64` has the same size and alignment.
+unsafe impl generic::AllowAtomic for u64 {
+ type Repr = i64;
+
+ fn into_repr(self) -> Self::Repr {
+ self as Self::Repr
+ }
+
+ fn from_repr(repr: Self::Repr) -> Self {
+ repr as Self
+ }
+}
+
+impl generic::AllowAtomicArithmetic for u64 {
+ type Delta = u64;
+
+ fn delta_into_repr(d: Self::Delta) -> Self::Repr {
+ d as Self::Repr
+ }
+}
+
+// SAFETY: `u32` and `i32` has the same size and alignment.
+unsafe impl generic::AllowAtomic for u32 {
+ type Repr = i32;
+
+ fn into_repr(self) -> Self::Repr {
+ self as Self::Repr
+ }
+
+ fn from_repr(repr: Self::Repr) -> Self {
+ repr as Self
+ }
+}
+
+impl generic::AllowAtomicArithmetic for u32 {
+ type Delta = u32;
+
+ fn delta_into_repr(d: Self::Delta) -> Self::Repr {
+ d as Self::Repr
+ }
+}
+
+use crate::macros::kunit_tests;
+
+#[kunit_tests(rust_atomics)]
+mod tests {
+ use super::*;
+
+ // Call $fn($val) with each $type of $val.
+ macro_rules! for_each_type {
+ ($val:literal in [$($type:ty),*] $fn:expr) => {
+ $({
+ let v: $type = $val;
+
+ $fn(v);
+ })*
+ }
+ }
+
+ #[test]
+ fn atomic_basic_tests() {
+ for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ let x = Atomic::new(v);
+
+ assert_eq!(v, x.load(Relaxed));
+ });
+ }
+
+ #[test]
+ fn atomic_xchg_tests() {
+ for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ let x = Atomic::new(v);
+
+ let old = v;
+ let new = v + 1;
+
+ assert_eq!(old, x.xchg(new, Full));
+ assert_eq!(new, x.load(Relaxed));
+ });
+ }
+
+ #[test]
+ fn atomic_cmpxchg_tests() {
+ for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ let x = Atomic::new(v);
+
+ let old = v;
+ let new = v + 1;
+
+ assert_eq!(Err(old), x.cmpxchg(new, new, Full));
+ assert_eq!(old, x.load(Relaxed));
+ assert_eq!(Ok(old), x.cmpxchg(old, new, Relaxed));
+ assert_eq!(new, x.load(Relaxed));
+ });
+ }
+
+ #[test]
+ fn atomic_arithmetic_tests() {
+ for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ let x = Atomic::new(v);
+
+ assert_eq!(v, x.fetch_add(12, Full));
+ assert_eq!(v + 12, x.load(Relaxed));
+
+ x.add(13, Relaxed);
+
+ assert_eq!(v + 25, x.load(Relaxed));
+ });
+ }
+}
--
2.39.5 (Apple Git-154)