Index: sys/rwlock.h
===================================================================
RCS file: /cvs/src/sys/sys/rwlock.h,v
retrieving revision 1.17
diff -u -p -r1.17 rwlock.h
--- sys/rwlock.h	10 Feb 2015 10:04:27 -0000	1.17
+++ sys/rwlock.h	10 Feb 2015 10:18:20 -0000
@@ -110,10 +110,6 @@ int rw_status(struct rwlock *);
  */
 #define RW_WRITE_OTHER	0x0100UL
 
-#ifndef rw_cas
-int rw_cas(volatile unsigned long *, unsigned long, unsigned long);
-#endif
-
 /* recursive rwlocks; */
 struct rrwlock {
 	struct rwlock	rrwl_lock;
Index: kern/kern_rwlock.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_rwlock.c,v
retrieving revision 1.24
diff -u -p -r1.24 kern_rwlock.c
--- kern/kern_rwlock.c	10 Feb 2015 10:04:27 -0000	1.24
+++ kern/kern_rwlock.c	10 Feb 2015 10:18:20 -0000
@@ -24,11 +24,23 @@
 #include <sys/limits.h>
 #include <sys/atomic.h>
 
-#include <machine/lock.h>
-
 /* XXX - temporary measure until proc0 is properly aligned */
 #define RW_PROC(p) (((long)p) & ~RWLOCK_MASK)
 
+#ifdef MULTIPROCESSOR
+#define rw_cas(p, o, n)	(atomic_cas_ulong(p, o, n) != o)
+#else
+static inline int
+rw_cas(volatile unsigned long *p, unsigned long o, unsigned long n)
+{
+	if (*p != o)
+		return (1);
+	*p = n;
+
+	return (0);
+}
+#endif
+
 /*
  * Magic wand for lock operations. Every operation checks if certain
  * flags are set and if they aren't, it increments the lock with some
@@ -123,18 +135,6 @@ rw_exit_write(struct rwlock *rwl)
 	    rw_cas(&rwl->rwl_owner, owner, 0)))
 		rw_exit(rwl);
 }
-
-#ifndef rw_cas
-int
-rw_cas(volatile unsigned long *p, unsigned long o, unsigned long n)
-{
-	if (*p != o)
-		return (1);
-	*p = n;
-
-	return (0);
-}
-#endif
 
 #ifdef DIAGNOSTIC
 /*