From 779a6a36961b50cd154da5705d9e6508f819cc4e Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Sun, 10 Jan 2016 13:19:38 +0200
Subject: [PATCH] s390: more efficient smp barriers

As per: lkml.kernel.org/r/20150921112252.3c2937e1@mschwide
atomics imply a barrier on s390, so s390 should change
smp_mb__before_atomic and smp_mb__after_atomic to barrier() instead of
smp_mb() and hence should not use the generic versions.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/s390/include/asm/barrier.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
index 4d26fa43ec90..5c8db3ce61c8 100644
--- a/arch/s390/include/asm/barrier.h
+++ b/arch/s390/include/asm/barrier.h
@@ -45,6 +45,9 @@ do {									\
 	___p1;								\
 })
 
+#define __smp_mb__before_atomic()	barrier()
+#define __smp_mb__after_atomic()	barrier()
+
 #include <asm-generic/barrier.h>
 
 #endif /* __ASM_BARRIER_H */
-- 
2.20.1