linux-kernel - [PATCH 10/11] ARC: cmpxchg/xchg: implement relaxed variants (LLSC config only)

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Message-Id: <20210804191554.1252776-11-vgupta@synopsys.com>
Date:   Wed,  4 Aug 2021 12:15:53 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     linux-snps-arc@...ts.infradead.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Vladimir Isaev <Vladimir.Isaev@...opsys.com>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [PATCH 10/11] ARC: cmpxchg/xchg: implement relaxed variants (LLSC config only)

It only makes sense to do this for the LLSC config

Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/arc/include/asm/cmpxchg.h | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 00deb076d6f6..e2ae0eb1ca07 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -38,7 +38,7 @@
 	_prev;								\
 })
 
-#define arch_cmpxchg(ptr, old, new)				        \
+#define arch_cmpxchg_relaxed(ptr, old, new)				\
 ({									\
 	__typeof__(ptr) _p_ = (ptr);					\
 	__typeof__(*(ptr)) _o_ = (old);					\
@@ -47,12 +47,7 @@
 									\
 	switch(sizeof((_p_))) {						\
 	case 4:								\
-	        /*							\
-		 * Explicit full memory barrier needed before/after	\
-	         */							\
-		smp_mb();						\
 		_prev_ = __cmpxchg(_p_, _o_, _n_);			\
-		smp_mb();						\
 		break;							\
 	default:							\
 		BUILD_BUG();						\
@@ -108,16 +103,14 @@
 	_val_;		/* get old value */				\
 })
 
-#define arch_xchg(ptr, val)						\
+#define arch_xchg_relaxed(ptr, val)					\
 ({									\
 	__typeof__(ptr) _p_ = (ptr);					\
 	__typeof__(*(ptr)) _val_ = (val);				\
 									\
 	switch(sizeof(*(_p_))) {					\
 	case 4:								\
-		smp_mb();						\
 		_val_ = __xchg(_p_, _val_);				\
-	        smp_mb();						\
 		break;							\
 	default:							\
 		BUILD_BUG();						\
-- 
2.25.1