[Xen-devel] [PATCH v3 41/41] s390: more efficient smp barriers

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Suggested-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
 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 4d26fa4..5c8db3c 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 */
-- 
MST


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