Index: head/sys/cddl/compat/opensolaris/sys/atomic.h
===================================================================
--- head/sys/cddl/compat/opensolaris/sys/atomic.h	(revision 353441)
+++ head/sys/cddl/compat/opensolaris/sys/atomic.h	(revision 353442)
@@ -1,155 +1,178 @@
 /*-
  * Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  * $FreeBSD$
  */
 
 #ifndef _OPENSOLARIS_SYS_ATOMIC_H_
 #define	_OPENSOLARIS_SYS_ATOMIC_H_
 
 #include <sys/types.h>
 #include <machine/atomic.h>
 
 #if defined(__i386__) && (defined(_KERNEL) || defined(KLD_MODULE))
 #define	I386_HAVE_ATOMIC64
 #endif
 
+#if defined(__i386__) || defined(__amd64__) || defined(__arm__)
+/* No spurious failures from fcmpset. */
+#define	STRONG_FCMPSET
+#endif
+
 #if !defined(__LP64__) && !defined(__mips_n32) && \
     !defined(ARM_HAVE_ATOMIC64) && !defined(I386_HAVE_ATOMIC64)
 extern void atomic_add_64(volatile uint64_t *target, int64_t delta);
 extern void atomic_dec_64(volatile uint64_t *target);
 extern uint64_t atomic_swap_64(volatile uint64_t *a, uint64_t value);
 extern uint64_t atomic_load_64(volatile uint64_t *a);
 extern uint64_t atomic_add_64_nv(volatile uint64_t *target, int64_t delta);
 extern uint64_t atomic_cas_64(volatile uint64_t *target, uint64_t cmp,
     uint64_t newval);
 #endif
 
 #define	membar_producer	atomic_thread_fence_rel
 
 static __inline uint32_t
 atomic_add_32_nv(volatile uint32_t *target, int32_t delta)
 {
 	return (atomic_fetchadd_32(target, delta) + delta);
 }
 
 static __inline u_int
 atomic_add_int_nv(volatile u_int *target, int delta)
 {
 	return (atomic_add_32_nv(target, delta));
 }
 
 static __inline void
 atomic_inc_32(volatile uint32_t *target)
 {
 	atomic_add_32(target, 1);
 }
 
 static __inline uint32_t
 atomic_inc_32_nv(volatile uint32_t *target)
 {
 	return (atomic_add_32_nv(target, 1));
 }
 
 static __inline void
 atomic_dec_32(volatile uint32_t *target)
 {
 	atomic_subtract_32(target, 1);
 }
 
 static __inline uint32_t
 atomic_dec_32_nv(volatile uint32_t *target)
 {
 	return (atomic_add_32_nv(target, -1));
 }
 
 #ifndef __sparc64__
 static inline uint32_t
 atomic_cas_32(volatile uint32_t *target, uint32_t cmp, uint32_t newval)
 {
+#ifdef STRONG_FCMPSET
 	(void)atomic_fcmpset_32(target, &cmp, newval);
+#else
+	uint32_t expected = cmp;
+
+	do {
+		if (atomic_fcmpset_32(target, &cmp, newval))
+			break;
+	} while (cmp == expected);
+#endif
 	return (cmp);
 }
 #endif
 
 #if defined(__LP64__) || defined(__mips_n32) || \
     defined(ARM_HAVE_ATOMIC64) || defined(I386_HAVE_ATOMIC64)
 static __inline void
 atomic_dec_64(volatile uint64_t *target)
 {
 	atomic_subtract_64(target, 1);
 }
 
 static inline uint64_t
 atomic_add_64_nv(volatile uint64_t *target, int64_t delta)
 {
 	return (atomic_fetchadd_64(target, delta) + delta);
 }
 
 #ifndef __sparc64__
 static inline uint64_t
 atomic_cas_64(volatile uint64_t *target, uint64_t cmp, uint64_t newval)
 {
+#ifdef STRONG_FCMPSET
 	(void)atomic_fcmpset_64(target, &cmp, newval);
+#else
+	uint64_t expected = cmp;
+
+	do {
+		if (atomic_fcmpset_64(target, &cmp, newval))
+			break;
+	} while (cmp == expected);
+#endif
 	return (cmp);
 }
 #endif
 #endif
 
 static __inline void
 atomic_inc_64(volatile uint64_t *target)
 {
 	atomic_add_64(target, 1);
 }
 
 static __inline uint64_t
 atomic_inc_64_nv(volatile uint64_t *target)
 {
 	return (atomic_add_64_nv(target, 1));
 }
 
 static __inline uint64_t
 atomic_dec_64_nv(volatile uint64_t *target)
 {
 	return (atomic_add_64_nv(target, -1));
 }
 
 #if !defined(COMPAT_32BIT) && defined(__LP64__)
 static __inline void *
 atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
 {
 	return ((void *)atomic_cas_64((volatile uint64_t *)target,
 	    (uint64_t)cmp, (uint64_t)newval));
 }
 #else
 static __inline void *
 atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
 {
 	return ((void *)atomic_cas_32((volatile uint32_t *)target,
 	    (uint32_t)cmp, (uint32_t)newval));
 }
 #endif	/* !defined(COMPAT_32BIT) && defined(__LP64__) */
 
 #endif	/* !_OPENSOLARIS_SYS_ATOMIC_H_ */