From: Bradley Morgan <brads@mainlining.org>
To: Andrew Morton <akpm@linux-foundation.org>,
Vineet Gupta <vgupta@kernel.org>, Guo Ren <guoren@kernel.org>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>, Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
David Laight <david.laight.linux@gmail.com>,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org,
linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org,
Bradley Morgan <brads@mainlining.org>
Subject: [PATCH v2 2/5] ARC: Emulate two-byte cmpxchg
Date: Wed, 16 Sep 2026 20:02:12 +0000 [thread overview]
Message-ID: <20260916200215.21774-3-brads@mainlining.org> (raw)
In-Reply-To: <20260916200215.21774-1-brads@mainlining.org>
ARC has no two-byte atomic compare and swap, so the __cmpxchg() macro
switch lets case 2 fall through to BUILD_BUG() via default. Route case
2 through the new cmpxchg_emu_u16(), which now takes natural u16
arguments, so the (uintptr_t) casts on _o_ and _n_ become (u16) casts.
Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
arch/arc/include/asm/cmpxchg.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 76f43db0890f..4451c2011ee3 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -50,6 +50,9 @@
case 1: \
_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *__force)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \
break; \
+ case 2: \
+ _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *__force)_p_, (u16)_o_, (u16)_n_); \
+ break; \
case 4: \
_prev_ = __cmpxchg(_p_, _o_, _n_); \
break; \
--
2.47.3
next prev parent reply other threads:[~2026-09-16 20:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 20:02 [PATCH v2 0/5] Add two-byte cmpxchg emulation and wire it into the architectures Bradley Morgan
2026-09-16 20:02 ` [PATCH v2 1/5] lib: Add two-byte cmpxchg emulation function Bradley Morgan
2026-09-16 20:17 ` Bradley Morgan
2026-09-16 20:02 ` Bradley Morgan [this message]
2026-09-16 20:02 ` [PATCH v2 3/5] csky: Emulate two-byte cmpxchg Bradley Morgan
2026-09-17 9:04 ` David Laight
2026-09-16 20:02 ` [PATCH v2 4/5] sh: " Bradley Morgan
2026-09-16 20:02 ` [PATCH v2 5/5] xtensa: " Bradley Morgan
2026-09-17 1:32 ` Max Filippov
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