linux-kernel - [PATCH 1/6] Revert "ARCv2: STAR 9000837815 workaround hardware exclusive transactions livelock"

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Message-ID: <1438596188-10875-2-git-send-email-vgupta@synopsys.com>
Date:	Mon, 3 Aug 2015 15:33:03 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	"Peter Zijlstra (Intel)" <peterz@...radead.org>
CC:	lkml <linux-kernel@...r.kernel.org>, <arc-linux-dev@...opsys.com>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [PATCH 1/6] Revert "ARCv2: STAR 9000837815 workaround hardware exclusive transactions livelock"

Extended testing of quad core configuration revealed that this fix was
insufficient. Specifically LTP open posix shm_op/23-1 would cause the
hardware livelock in llock/scond loop in update_cpu_load_active()

So remove this and make way for a proper workaround

This reverts commit a5c8b52abe677977883655166796f167ef1e0084.

Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/arc/include/asm/atomic.h | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 03484cb4d16d..20b7dc17979e 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -23,21 +23,13 @@
 
 #define atomic_set(v, i) (((v)->counter) = (i))
 
-#ifdef CONFIG_ISA_ARCV2
-#define PREFETCHW	"	prefetchw   [%1]	\n"
-#else
-#define PREFETCHW
-#endif
-
 #define ATOMIC_OP(op, c_op, asm_op)					\
 static inline void atomic_##op(int i, atomic_t *v)			\
 {									\
 	unsigned int temp;						\
 									\
 	__asm__ __volatile__(						\
-	"1:				\n"				\
-	PREFETCHW							\
-	"	llock   %0, [%1]	\n"				\
+	"1:	llock   %0, [%1]	\n"				\
 	"	" #asm_op " %0, %0, %2	\n"				\
 	"	scond   %0, [%1]	\n"				\
 	"	bnz     1b		\n"				\
@@ -58,9 +50,7 @@ static inline int atomic_##op##_return(int i, atomic_t *v)		\
 	smp_mb();							\
 									\
 	__asm__ __volatile__(						\
-	"1:				\n"				\
-	PREFETCHW							\
-	"	llock   %0, [%1]	\n"				\
+	"1:	llock   %0, [%1]	\n"				\
 	"	" #asm_op " %0, %0, %2	\n"				\
 	"	scond   %0, [%1]	\n"				\
 	"	bnz     1b		\n"				\
-- 
1.9.1

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