linux-kernel - [PATCH v4 08/10] riscv: Remove arch specific __atomic_acquire/release

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Message-ID: <20251020042457.30915-4-luxu.kernel@bytedance.com>
Date: Mon, 20 Oct 2025 12:24:55 +0800
From: Xu Lu <luxu.kernel@...edance.com>
To: corbet@....net,
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	palmer@...belt.com,
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	Xu Lu <luxu.kernel@...edance.com>
Subject: [PATCH v4 08/10] riscv: Remove arch specific __atomic_acquire/release_fence

Remove arch specific __atomic_acquire/release_fence() operations since
they use fence instruction to simulate acquire/release order and can not
work well with real acquire/release instructions.

The default generic __atomic_acuire/release_fence() now provide sequential
order via 'fennce rw, rw'. They are rarely called since we use real
acquire/release instructions in most of times.

Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
---
 arch/riscv/include/asm/atomic.h | 6 ------
 arch/riscv/include/asm/fence.h  | 4 ----
 2 files changed, 10 deletions(-)

diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h
index 86291de07de62..6ed50a283bf8b 100644
--- a/arch/riscv/include/asm/atomic.h
+++ b/arch/riscv/include/asm/atomic.h
@@ -18,12 +18,6 @@
 
 #include <asm/cmpxchg.h>
 
-#define __atomic_acquire_fence()					\
-	__asm__ __volatile__(RISCV_ACQUIRE_BARRIER "" ::: "memory")
-
-#define __atomic_release_fence()					\
-	__asm__ __volatile__(RISCV_RELEASE_BARRIER "" ::: "memory");
-
 static __always_inline int arch_atomic_read(const atomic_t *v)
 {
 	return READ_ONCE(v->counter);
diff --git a/arch/riscv/include/asm/fence.h b/arch/riscv/include/asm/fence.h
index 182db7930edc2..9ce83e4793948 100644
--- a/arch/riscv/include/asm/fence.h
+++ b/arch/riscv/include/asm/fence.h
@@ -7,12 +7,8 @@
 	({ __asm__ __volatile__ (RISCV_FENCE_ASM(p, s) : : : "memory"); })
 
 #ifdef CONFIG_SMP
-#define RISCV_ACQUIRE_BARRIER		RISCV_FENCE_ASM(r, rw)
-#define RISCV_RELEASE_BARRIER		RISCV_FENCE_ASM(rw, w)
 #define RISCV_FULL_BARRIER		RISCV_FENCE_ASM(rw, rw)
 #else
-#define RISCV_ACQUIRE_BARRIER
-#define RISCV_RELEASE_BARRIER
 #define RISCV_FULL_BARRIER
 #endif
 
-- 
2.20.1