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Message-ID: <175775853344.709179.11140241381449108544.tip-bot2@tip-bot2>
Date: Sat, 13 Sep 2025 10:15:33 -0000
From: "tip-bot2 for Boqun Feng" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Boqun Feng <boqun.feng@...il.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Alice Ryhl <aliceryhl@...gle.com>, Andreas Hindborg <a.hindborg@...nel.org>,
Benno Lossin <lossin@...nel.org>, Elle Rhumsaa <elle@...thered-steel.dev>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: locking/core] rust: sync: atomic: Add Atomic<{usize,isize}>
The following commit has been merged into the locking/core branch of tip:
Commit-ID: c0231e3023da14fa5549fbb21fec1820520a6eeb
Gitweb: https://git.kernel.org/tip/c0231e3023da14fa5549fbb21fec1820520a6eeb
Author: Boqun Feng <boqun.feng@...il.com>
AuthorDate: Thu, 04 Sep 2025 21:41:35 -07:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Sat, 13 Sep 2025 12:07:58 +02:00
rust: sync: atomic: Add Atomic<{usize,isize}>
Add generic atomic support for `usize` and `isize`. Note that instead of
mapping directly to `atomic_long_t`, the represention type
(`AtomicType::Repr`) is selected based on CONFIG_64BIT. This reduces
the necessity of creating `atomic_long_*` helpers, which could save
the binary size of kernel if inline helpers are not available. To do so,
an internal type `isize_atomic_repr` is defined, it's `i32` in 32bit
kernel and `i64` in 64bit kernel.
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
Reviewed-by: Andreas Hindborg <a.hindborg@...nel.org>
Reviewed-by: Benno Lossin <lossin@...nel.org>
Reviewed-by: Elle Rhumsaa <elle@...thered-steel.dev>
Link: https://lore.kernel.org/all/20250719030827.61357-9-boqun.feng@gmail.com/
---
rust/kernel/sync/atomic/predefine.rs | 53 ++++++++++++++++++++++++---
1 file changed, 49 insertions(+), 4 deletions(-)
diff --git a/rust/kernel/sync/atomic/predefine.rs b/rust/kernel/sync/atomic/predefine.rs
index d087581..45a1798 100644
--- a/rust/kernel/sync/atomic/predefine.rs
+++ b/rust/kernel/sync/atomic/predefine.rs
@@ -2,6 +2,9 @@
//! Pre-defined atomic types
+use crate::static_assert;
+use core::mem::{align_of, size_of};
+
// SAFETY: `i32` has the same size and alignment with itself, and is round-trip transmutable to
// itself.
unsafe impl super::AtomicType for i32 {
@@ -28,6 +31,35 @@ unsafe impl super::AtomicAdd<i64> for i64 {
}
}
+// Defines an internal type that always maps to the integer type which has the same size alignment
+// as `isize` and `usize`, and `isize` and `usize` are always bi-directional transmutable to
+// `isize_atomic_repr`, which also always implements `AtomicImpl`.
+#[allow(non_camel_case_types)]
+#[cfg(not(CONFIG_64BIT))]
+type isize_atomic_repr = i32;
+#[allow(non_camel_case_types)]
+#[cfg(CONFIG_64BIT)]
+type isize_atomic_repr = i64;
+
+// Ensure size and alignment requirements are checked.
+static_assert!(size_of::<isize>() == size_of::<isize_atomic_repr>());
+static_assert!(align_of::<isize>() == align_of::<isize_atomic_repr>());
+static_assert!(size_of::<usize>() == size_of::<isize_atomic_repr>());
+static_assert!(align_of::<usize>() == align_of::<isize_atomic_repr>());
+
+// SAFETY: `isize` has the same size and alignment with `isize_atomic_repr`, and is round-trip
+// transmutable to `isize_atomic_repr`.
+unsafe impl super::AtomicType for isize {
+ type Repr = isize_atomic_repr;
+}
+
+// SAFETY: The wrapping add result of two `isize_atomic_repr`s is a valid `usize`.
+unsafe impl super::AtomicAdd<isize> for isize {
+ fn rhs_into_delta(rhs: isize) -> isize_atomic_repr {
+ rhs as isize_atomic_repr
+ }
+}
+
// SAFETY: `u32` and `i32` has the same size and alignment, and `u32` is round-trip transmutable to
// `i32`.
unsafe impl super::AtomicType for u32 {
@@ -54,6 +86,19 @@ unsafe impl super::AtomicAdd<u64> for u64 {
}
}
+// SAFETY: `usize` has the same size and alignment with `isize_atomic_repr`, and is round-trip
+// transmutable to `isize_atomic_repr`.
+unsafe impl super::AtomicType for usize {
+ type Repr = isize_atomic_repr;
+}
+
+// SAFETY: The wrapping add result of two `isize_atomic_repr`s is a valid `usize`.
+unsafe impl super::AtomicAdd<usize> for usize {
+ fn rhs_into_delta(rhs: usize) -> isize_atomic_repr {
+ rhs as isize_atomic_repr
+ }
+}
+
use crate::macros::kunit_tests;
#[kunit_tests(rust_atomics)]
@@ -73,7 +118,7 @@ mod tests {
#[test]
fn atomic_basic_tests() {
- for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {
let x = Atomic::new(v);
assert_eq!(v, x.load(Relaxed));
@@ -82,7 +127,7 @@ mod tests {
#[test]
fn atomic_xchg_tests() {
- for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {
let x = Atomic::new(v);
let old = v;
@@ -95,7 +140,7 @@ mod tests {
#[test]
fn atomic_cmpxchg_tests() {
- for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {
let x = Atomic::new(v);
let old = v;
@@ -110,7 +155,7 @@ mod tests {
#[test]
fn atomic_arithmetic_tests() {
- for_each_type!(42 in [i32, i64, u32, u64] |v| {
+ for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {
let x = Atomic::new(v);
assert_eq!(v, x.fetch_add(12, Full));
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