From: Bradley Morgan <brads@mainlining.org>
To: akpm@linux-foundation.org, vgupta@kernel.org, guoren@kernel.org,
chris@zankel.net, jcmvbkbc@gmail.com
Cc: arnd@arndb.de, paulmck@kernel.org, david.laight.linux@gmail.com,
glaubitz@physik.fu-berlin.de, ysato@users.sourceforge.jp,
dalias@libc.org, linux-snps-arc@lists.infradead.org,
linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org,
brads@mainlining.org
Subject: [PATCH v5 2/3] csky: Emulate two-byte cmpxchg
Date: Mon, 5 Oct 2026 12:05:55 +0000 [thread overview]
Message-ID: <20261005120556.383004-3-brads@mainlining.org> (raw)
In-Reply-To: <20261005120556.383004-1-brads@mainlining.org>
C-SKY has no two-byte atomic compare and swap, so the __cmpxchg()
macros let case 2 fall through to BUILD_BUG() via default, and a
two-byte cmpxchg() fails the build.
Route case 2 through the new cmpxchg_emu_u16(), which narrows the
old and new values itself, so all three orderings, relaxed, acquire
and full, keep the (uintptr_t) casts the case 1 path already uses.
Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
arch/csky/include/asm/cmpxchg.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index db6dda47184e..6f3ca79e54ac 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -64,6 +64,9 @@
switch (size) { \
case 1: \
__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+ break; \
+ case 2: \
+ __ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
break; \
case 4: \
asm volatile ( \
@@ -97,6 +100,9 @@
switch (size) { \
case 1: \
__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+ break; \
+ case 2: \
+ __ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
break; \
case 4: \
asm volatile ( \
@@ -131,6 +137,9 @@
switch (size) { \
case 1: \
__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
+ break; \
+ case 2: \
+ __ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (unsigned long)__old, (unsigned long)__new); \
break; \
case 4: \
asm volatile ( \
--
2.53.0
next prev parent reply other threads:[~2026-10-05 12:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-05 12:05 [PATCH v5 0/3] Add two-byte cmpxchg emulation and wire it into the architectures Bradley Morgan
2026-10-05 12:05 ` [PATCH v5 1/3] ARC: Emulate two-byte cmpxchg Bradley Morgan
2026-10-05 12:08 ` Bradley Morgan
2026-10-05 12:05 ` Bradley Morgan [this message]
2026-10-05 12:05 ` [PATCH v5 3/3] xtensa: " Bradley Morgan
2026-10-05 12:06 [PATCH v5 0/3] Add two-byte cmpxchg emulation and wire it into the architectures Bradley Morgan
2026-10-05 12:06 ` [PATCH v5 2/3] csky: Emulate two-byte cmpxchg Bradley Morgan
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