Index: alpha/mutex.c
===================================================================
RCS file: /cvs/src/sys/arch/alpha/alpha/mutex.c,v
retrieving revision 1.13
diff -u -p -r1.13 mutex.c
--- alpha/mutex.c	11 Feb 2015 01:15:06 -0000	1.13
+++ alpha/mutex.c	16 Apr 2015 10:28:26 -0000
@@ -28,6 +28,7 @@
 #include <sys/param.h>
 #include <sys/mutex.h>
 #include <sys/systm.h>
+#include <sys/atomic.h>
 
 #include <machine/intr.h>
 #include <machine/lock.h>
@@ -38,40 +39,19 @@ static inline int
 try_lock(struct mutex *mtx)
 {
 #ifdef MULTIPROCESSOR
-	unsigned long t0, v0;
-
-	__asm volatile(
-		"1:	ldl_l	%0, %3		\n"	/* t0 = mtx->mtx_lock */
-		"	bne	%0, 2f		\n"
-		"	bis	$31, 1, %0	\n"	/* t0 = 1 */
-		"	stl_c	%0, %2		\n"	/* mtx->mtx_lock = 1 */
-		"	beq	%0, 3f		\n"
-		"	mb			\n"
-		"	bis	$31, 1, %1	\n"	/* v0 = 1 */
-		"	br	4f		\n"
-		"3:	br	1b		\n"	/* update failed */
-		"2:	bis	$31, $31, %1	\n"	/* v0 = 0 */
-		"4:				\n"
-		: "=&r" (t0), "=r" (v0), "=m" (mtx->mtx_lock)
-		: "m" (mtx->mtx_lock)
-		: "memory");
-
-	return (v0 != 0);
+	return (atomic_cas_ptr(&mtx->mtx_owner, NULL, curcpu()) == NULL);
 #else
-	mtx->mtx_lock = 1;
-	return 1;
+	mtx->mtx_owner = curcpu();
+	return (1);
 #endif
 }
 
 void
 __mtx_init(struct mutex *mtx, int wantipl)
 {
+	mtx->mtx_owner = NULL;
 	mtx->mtx_oldipl = IPL_NONE;
 	mtx->mtx_wantipl = wantipl;
-	mtx->mtx_lock = 0;
-#ifdef MULTIPROCESSOR
-	mtx->mtx_owner = NULL;
-#endif
 }
 
 void
@@ -85,10 +65,12 @@ mtx_enter(struct mutex *mtx)
 		if (try_lock(mtx)) {
 			if (mtx->mtx_wantipl != IPL_NONE)
 				mtx->mtx_oldipl = s;
-			mtx->mtx_owner = curcpu();
 #ifdef DIAGNOSTIC
 			curcpu()->ci_mutex_level++;
 #endif
+#ifdef MULTIPROCESSOR
+			membar_enter();
+#endif
 			return;
 		}
 		if (mtx->mtx_wantipl != IPL_NONE)
@@ -110,7 +92,6 @@ mtx_enter_try(struct mutex *mtx)
 	if (try_lock(mtx)) {
 		if (mtx->mtx_wantipl != IPL_NONE)
 			mtx->mtx_oldipl = s;
-		mtx->mtx_owner = curcpu();
 #ifdef DIAGNOSTIC
 		curcpu()->ci_mutex_level++;
 #endif
@@ -132,9 +113,8 @@ mtx_leave(struct mutex *mtx)
 #endif
 	s = mtx->mtx_oldipl;
 	mtx->mtx_owner = NULL;
-	mtx->mtx_lock = 0;
 #ifdef MULTIPROCESSOR
-	alpha_wmb();
+	membar_exit();
 #endif
 	if (mtx->mtx_wantipl != IPL_NONE)
 		splx(s);
Index: include/mutex.h
===================================================================
RCS file: /cvs/src/sys/arch/alpha/include/mutex.h,v
retrieving revision 1.6
diff -u -p -r1.6 mutex.h
--- include/mutex.h	18 Mar 2014 21:09:28 -0000	1.6
+++ include/mutex.h	16 Apr 2015 10:28:26 -0000
@@ -29,10 +29,9 @@
 #define _MACHINE_MUTEX_H_
 
 struct mutex {
-	int mtx_lock;
+	void *mtx_owner;
 	int mtx_wantipl;
 	int mtx_oldipl;
-	void *mtx_owner;
 };
 
 /*
@@ -49,7 +48,7 @@ struct mutex {
 #define __MUTEX_IPL(ipl) (ipl)
 #endif
 
-#define MUTEX_INITIALIZER(ipl) { 0, __MUTEX_IPL((ipl)), IPL_NONE, NULL }
+#define MUTEX_INITIALIZER(ipl) { NULL, __MUTEX_IPL((ipl)), IPL_NONE }
 
 void __mtx_init(struct mutex *, int);
 #define mtx_init(mtx, ipl) __mtx_init((mtx), __MUTEX_IPL((ipl)))
@@ -57,7 +56,7 @@ void __mtx_init(struct mutex *, int);
 #ifdef DIAGNOSTIC
 #ifdef MULTIPROCESSOR
 #define MUTEX_ASSERT_LOCKED(mtx) do {					\
-	if ((mtx)->mtx_lock == 0)					\
+	if ((mtx)->mtx_owner == NULL)					\
 		panic("mutex %p not held in %s", (mtx), __func__);	\
 	if ((mtx)->mtx_owner != curcpu())				\
 		panic("mutex %p held by cpu %p in %s",			\
@@ -65,13 +64,13 @@ void __mtx_init(struct mutex *, int);
 } while (0)
 #else
 #define MUTEX_ASSERT_LOCKED(mtx) do {					\
-	if ((mtx)->mtx_lock == 0)					\
+	if ((mtx)->mtx_owner == NULL)					\
 		panic("mutex %p not held in %s", (mtx), __func__);	\
 } while (0)
 #endif
 
 #define MUTEX_ASSERT_UNLOCKED(mtx) do {					\
-	if ((mtx)->mtx_lock != 0)					\
+	if ((mtx)->mtx_owner == curcpu())				\
 		panic("mutex %p held in %s", (mtx), __func__);		\
 } while (0)
 #else