[PATCH v6 7/9] rust: sync: atomic: Add Atomic<u{32,64}>

Boqun Feng
2025-07-10T06:01:09Z

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>.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
rust/kernel/sync/atomic.rs | 99 ++++++++++++++++++++++++++++++++++++++
1 file changed, 99 insertions(+)

diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
index 26f66cccd4e0..e676bc7d9275 100644
--- a/rust/kernel/sync/atomic.rs
+++ b/rust/kernel/sync/atomic.rs
@@ -52,3 +52,102 @@ fn delta_into_repr(d: Self::Delta) -> Self::Repr {
d
}
}
+
+// SAFETY: `u32` and `i32` has the same size and alignment, and `u32` is round-trip transmutable to
+// `i32`.
+unsafe impl generic::AllowAtomic for u32 {
+ type Repr = i32;
+}
+
+// SAFETY: `i32` is always sound to transmute back to `u32`.
+unsafe impl generic::AllowAtomicArithmetic for u32 {
+ type Delta = u32;
+
+ fn delta_into_repr(d: Self::Delta) -> Self::Repr {
+ d as Self::Repr
+ }
+}
+
+// SAFETY: `u64` and `i64` has the same size and alignment, and `u64` is round-trip transmutable to
+// `i64`.
+unsafe impl generic::AllowAtomic for u64 {
+ type Repr = i64;
+}
+
+// SAFETY: `i64` is always sound to transmute back to `u64`.
+unsafe impl generic::AllowAtomicArithmetic for u64 {
+ type Delta = u64;
+
+ 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)