add memory barriers

- rmb()
- wmb()

arch/x86/kernel/include/arch/cpu.h

@@ -0,0 +1,28 @@
+/**
+ * \file cpu.h
+ *  License details are found in the file LICENSE.
+ * \brief
+ *  Declare architecture-dependent types and functions to control CPU.
+ * \author Gou Nakamura  <go.nakamura.yw@hitachi-solutions.com>
+ *      Copyright (C) 2015  RIKEN AICS
+ */
+/*
+ * HISTORY
+ */
+
+#ifndef ARCH_CPU_H
+#define ARCH_CPU_H
+
+#include <ihk/cpu.h>
+
+static inline void rmb(void)
+{
+	barrier();
+}
+
+static inline void wmb(void)
+{
+	barrier();
+}
+
+#endif /* ARCH_CPU_H */