v4.19.13 snapshot.
diff --git a/arch/xtensa/include/asm/barrier.h b/arch/xtensa/include/asm/barrier.h
new file mode 100644
index 0000000..956596e
--- /dev/null
+++ b/arch/xtensa/include/asm/barrier.h
@@ -0,0 +1,21 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 - 2012 Tensilica Inc.
+ */
+
+#ifndef _XTENSA_SYSTEM_H
+#define _XTENSA_SYSTEM_H
+
+#define mb() ({ __asm__ __volatile__("memw" : : : "memory"); })
+#define rmb() barrier()
+#define wmb() mb()
+
+#define __smp_mb__before_atomic() barrier()
+#define __smp_mb__after_atomic() barrier()
+
+#include <asm-generic/barrier.h>
+
+#endif /* _XTENSA_SYSTEM_H */