Index: sys/sys/buf_ring.h
===================================================================
--- sys/sys/buf_ring.h
+++ sys/sys/buf_ring.h
@@ -94,18 +94,50 @@
  * - Some effort is made to avoid extra memory barriers by using one 
  *   atomic_<>_acq_32 operation to guarantee the value of multiple values
  */
+#ifdef DEBUG_BUFRING
+#define DUPLICATE_CHECK(br, buf)								\
+	do {											\
+		int i;										\
+		for (i = br->br_cons_head; i != br->br_prod_head;				\
+			 i = ((i + 1) & br->br_cons_mask))					\
+			if(br->br_ring[i] == buf)						\
+				panic("buf=%p already enqueue at %d prod=%d cons=%d",	\
+					  buf, i, br->br_prod_tail, br->br_cons_tail);		\
+	} while (0)
+#define DEQUEUE_VALIDATE(br, cons_head)								\
+	do {											\
+		br->br_ring[cons_head] = NULL;							\
+		if (!mtx_owned(br->br_lock))							\
+			panic("lock not held on single consumer dequeue");			\
+		if (br->br_cons_tail != cons_head)						\
+			panic("inconsistent list cons_tail=%d cons_head=%d",	\
+				  br->br_cons_tail, cons_head);					\
+	} while (0)
+#else
+#define DUPLICATE_CHECK(br, buf)
+#define DEQUEUE_VALIDATE(br, cons_head)
+#endif
+
+#ifdef PREFETCH_DEFINED
+#define DEQUEUE_PREFETCH(br, cons_head, cons_next, prod_tail)			\
+	do {									\
+		uint32_t cons_next_next = (cons_head + 2) & br->br_cons_mask;	\
+		if (cons_next != prod_tail) {					\
+			prefetch(br->br_ring[cons_next]);			\
+			if (cons_next_next != prod_tail)			\
+				prefetch(br->br_ring[cons_next_next]);		\
+		}								\
+	} while (0)
+#else
+#define DEQUEUE_PREFETCH(br, cons_head, cons_next, prod_tail)
+#endif
+
 static __inline int
 buf_ring_enqueue(struct buf_ring *br, void *buf)
 {
 	uint32_t prod_head, prod_next, cons_tail;
-#ifdef DEBUG_BUFRING
-	int i;
-	for (i = br->br_cons_head; i != br->br_prod_head;
-	     i = ((i + 1) & br->br_cons_mask))
-		if(br->br_ring[i] == buf)
-			panic("buf=%p already enqueue at %d prod=%d cons=%d",
-			    buf, i, br->br_prod_tail, br->br_cons_tail);
-#endif	
+
+	DUPLICATE_CHECK(br, buf);
 	critical_enter();
 	cons_tail = atomic_load_acq_32(&br->br_cons_tail);
 	do {
@@ -198,9 +230,6 @@
 buf_ring_dequeue_sc(struct buf_ring *br)
 {
 	uint32_t cons_head, cons_next;
-#ifdef PREFETCH_DEFINED
-	uint32_t cons_next_next;
-#endif
 	uint32_t prod_tail;
 	void *buf;
 	
@@ -210,25 +239,11 @@
 		return (NULL);
 	
 	cons_next = (cons_head + 1) & br->br_cons_mask;
-#ifdef PREFETCH_DEFINED
-	cons_next_next = (cons_head + 2) & br->br_cons_mask;
-	if (cons_next != prod_tail) {		
-		prefetch(br->br_ring[cons_next]);
-		if (cons_next_next != prod_tail) 
-			prefetch(br->br_ring[cons_next_next]);
-	}
-#endif
+	DEQUEUE_PREFETCH(br, cons_head, cons_next, prod_tail);
 	br->br_cons_head = cons_next;
 	buf = br->br_ring[cons_head];
 
-#ifdef DEBUG_BUFRING
-	br->br_ring[cons_head] = NULL;
-	if (!mtx_owned(br->br_lock))
-		panic("lock not held on single consumer dequeue");
-	if (br->br_cons_tail != cons_head)
-		panic("inconsistent list cons_tail=%d cons_head=%d",
-		    br->br_cons_tail, cons_head);
-#endif
+	DEQUEUE_VALIDATE(br, cons_head);
 	/* do atomic_store_rel_32 to assure that producer has
 	* up to date view
 	*/