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

Commit-ID:     164e4b5600b32b4ddeac58bb5b37bc1490a1dce4
Gitweb:        https://git.kernel.org/tip/164e4b5600b32b4ddeac58bb5b37bc1490a1dce4
Author:        FUJITA Tomonori <fujita.tomonori@gmail.com>
AuthorDate:    Sat, 27 Dec 2025 20:59:48 +09:00
Committer:     Boqun Feng <boqun.feng@gmail.com>
CommitterDate: Fri, 09 Jan 2026 19:01:41 +08:00

rust: helpers: Add i8/i16 atomic try_cmpxchg helpers

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

[boqun: Add comments explaining CONFIG_ARCH_SUPPORTS_ATOMIC_RMW and use
try_cmpxchg() instead of raw_try_cmpxchg()]

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251227115951.1424458-2-fujita.tomonori@gmail.com
---
 rust/helpers/atomic_ext.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/rust/helpers/atomic_ext.c b/rust/helpers/atomic_ext.c
index 76e392c..5ee127f 100644
--- a/rust/helpers/atomic_ext.c
+++ b/rust/helpers/atomic_ext.c
@@ -90,3 +90,20 @@ __rust_helper s16 rust_helper_atomic_i16_xchg_relaxed(s16 *ptr, s16 new)
 {
 	return xchg_relaxed(ptr, new);
 }
+
+/*
+ * try_cmpxchg helpers depend on ARCH_SUPPORTS_ATOMIC_RMW and on the
+ * architecture provding try_cmpxchg() support for i8 and i16.
+ *
+ * The architectures that currently support Rust (x86_64, armv7,
+ * arm64, riscv, and loongarch) satisfy these requirements.
+ */
+__rust_helper bool rust_helper_atomic_i8_try_cmpxchg(s8 *ptr, s8 *old, s8 new)
+{
+	return try_cmpxchg(ptr, old, new);
+}
+
+__rust_helper bool rust_helper_atomic_i16_try_cmpxchg(s16 *ptr, s16 *old, s16 new)
+{
+	return try_cmpxchg(ptr, old, new);
+}