linux-kernel - [PATCH 07/36] rust: helpers: Add i8/i16 atomic xchg helpers

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Message-ID: <20260111120209.6133-5-boqun.feng@gmail.com>
Date: Sun, 11 Jan 2026 20:01:40 +0800
From: Boqun Feng <boqun.feng@...il.com>
To: "Peter Zijlstra" <peterz@...radead.org>,
	"Ingo Molnar" <mingo@...nel.org>
Cc: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Will Deacon" <will@...nel.org>,
	"Mark Rutland" <mark.rutland@....com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Miguel Ojeda" <ojeda@...nel.org>,
	"Gary Guo" <gary@...yguo.net>,
	"Alice Ryhl" <aliceryhl@...gle.com>,
	"Andreas Hindborg" <a.hindborg@...nel.org>,
	"Benno Lossin" <lossin@...nel.org>,
	"Danilo Krummrich" <dakr@...nel.org>,
	FUJITA Tomonori <fujita.tomonori@...il.com>,
	Boqun Feng <boqun.feng@...il.com>
Subject: [PATCH 07/36] rust: helpers: Add i8/i16 atomic xchg helpers

From: FUJITA Tomonori <fujita.tomonori@...il.com>

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@...gle.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
Reviewed-by: Gary Guo <gary@...yguo.net>
Signed-off-by: Boqun Feng <boqun.feng@...il.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 02e05b4246ae..3136255a84c6 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);
+}
-- 
2.51.0