The following commit has been merged into the locking/core branch of tip:

Commit-ID:     5dbc0a692459bc49cdb7add281086291da547750
Gitweb:        https://git.kernel.org/tip/5dbc0a692459bc49cdb7add281086291da547750
Author:        FUJITA Tomonori <fujita.tomonori@gmail.com>
AuthorDate:    Tue, 23 Dec 2025 15:21:37 +09:00
Committer:     Boqun Feng <boqun.feng@gmail.com>
CommitterDate: Fri, 09 Jan 2026 19:01:40 +08:00

rust: helpers: Add i8/i16 atomic xchg helpers

Add i8/i16 atomic xchg helpers that call xchg() macro implementing
atomic xchg using architecture-specific instructions.

[boqun: Use xchg() instead of raw_xchg()]

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251223062140.938325-2-fujita.tomonori@gmail.com
---
 rust/helpers/atomic_ext.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/rust/helpers/atomic_ext.c b/rust/helpers/atomic_ext.c
index 02e05b4..3136255 100644
--- a/rust/helpers/atomic_ext.c
+++ b/rust/helpers/atomic_ext.c
@@ -2,6 +2,7 @@
 
 #include <asm/barrier.h>
 #include <asm/rwonce.h>
+#include <linux/atomic.h>
 
 __rust_helper s8 rust_helper_atomic_i8_read(s8 *ptr)
 {
@@ -42,3 +43,20 @@ __rust_helper void rust_helper_atomic_i16_set_release(s16 *ptr, s16 val)
 {
 	smp_store_release(ptr, val);
 }
+
+/*
+ * xchg helpers depend on ARCH_SUPPORTS_ATOMIC_RMW and on the
+ * architecture provding xchg() support for i8 and i16.
+ *
+ * The architectures that currently support Rust (x86_64, armv7,
+ * arm64, riscv, and loongarch) satisfy these requirements.
+ */
+__rust_helper s8 rust_helper_atomic_i8_xchg(s8 *ptr, s8 new)
+{
+	return xchg(ptr, new);
+}
+
+__rust_helper s16 rust_helper_atomic_i16_xchg(s16 *ptr, s16 new)
+{
+	return xchg(ptr, new);
+}