+#ifndef _ARCH_ATOMIC_S390_H
+#define _ARCH_ATOMIC_S390_H
+
+/*
+ * Atomic exchange operations for the S390 architecture.
+ *
+ * Copyright (C) 2009 Novell, Inc.
+ * Author: Jan Blunck <jblunck@suse.de>
+ *
+ * This is taken from the Principles of Operation Appendix A "Conditional
+ * Swapping Instructions (CS, CDS)".
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License version 2.1 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __SIZEOF_LONG__
+#ifdef __s390x__
+#define __SIZEOF_LONG__ 8
+#else
+#define __SIZEOF_LONG__ 4
+#endif
+#endif
+
+#ifndef BITS_PER_LONG
+#define BITS_PER_LONG (__SIZEOF_LONG__ * 8)
+#endif
+
+#ifndef _INCLUDE_API_H
+
+static __attribute__((always_inline))
+unsigned int atomic_exchange_32(volatile unsigned int *addr, unsigned int val)
+{
+ unsigned int result;
+
+ __asm__ __volatile__(
+ "0: cs %0,%2,%1\n"
+ " brc 4,0b\n"
+ : "=&r"(result), "=m" (*addr)
+ : "r"(val), "m" (*addr)
+ : "memory", "cc");
+
+ return result;
+}
+
+#if (BITS_PER_LONG == 64)
+
+static __attribute__((always_inline))
+unsigned long atomic_exchange_64(volatile unsigned long *addr,
+ unsigned long val)
+{
+ unsigned long result;
+
+ __asm__ __volatile__(
+ "0: csg %0,%2,%1\n"
+ " brc 4,0b\n"
+ : "=&r"(result), "=m" (*addr)
+ : "r"(val), "m" (*addr)
+ : "memory", "cc");
+
+ return result;
+}
+
+#endif
+
+static __attribute__((always_inline))
+unsigned long _atomic_exchange(volatile void *addr, unsigned long val, int len)
+{
+ switch (len) {
+ case 4:
+ return atomic_exchange_32(addr, val);
+#if (BITS_PER_LONG == 64)
+ case 8:
+ return atomic_exchange_64(addr, val);
+#endif
+ default:
+ __asm__ __volatile__(".long 0xd00d00");
+ }
+
+ return 0;
+}
+
+#define xchg(addr, v) (__typeof__(*(addr))) _atomic_exchange((addr), (v), \
+ sizeof(*(addr)))
+
+#endif /* #ifndef _INCLUDE_API_H */
+
+#endif /* ARCH_ATOMIC_S390_H */