--- /dev/null
+#ifndef _URCU_ARCH_ATOMIC_S390_H
+#define _URCU_ARCH_ATOMIC_S390_H
+
+/*
+ * Atomic exchange operations for the S390 architecture. Based on information
+ * taken from the Principles of Operation Appendix A "Conditional Swapping
+ * Instructions (CS, CDS)".
+ *
+ * Copyright (c) 2009 Novell, Inc.
+ * Author: Jan Blunck <jblunck@suse.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#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
+
+static inline __attribute__((always_inline))
+unsigned int uatomic_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 inline __attribute__((always_inline))
+unsigned long uatomic_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 inline __attribute__((always_inline))
+unsigned long _uatomic_exchange(volatile void *addr, unsigned long val, int len)
+{
+ switch (len) {
+ case 4:
+ return uatomic_exchange_32(addr, val);
+#if (BITS_PER_LONG == 64)
+ case 8:
+ return uatomic_exchange_64(addr, val);
+#endif
+ default:
+ __asm__ __volatile__(".long 0xd00d00");
+ }
+
+ return 0;
+}
+
+#define uatomic_xchg(addr, v) \
+ (__typeof__(*(addr))) _uatomic_exchange((addr), (unsigned long)(v), \
+ sizeof(*(addr)))
+
+#endif /* _URCU_ARCH_ATOMIC_S390_H */