Index: sys/sys/buf_ring.h
===================================================================
--- sys/sys/buf_ring.h
+++ sys/sys/buf_ring.h
@@ -95,6 +95,7 @@
 		panic("dangling value in enqueue");
 #endif	
 	br->br_ring[prod_head] = buf;
+	wmb();
 
 	/*
 	 * If there are other enqueues in progress
@@ -173,6 +174,7 @@
 	if (cons_head == prod_tail) 
 		return (NULL);
 
+	rmb();
 #ifdef PREFETCH_DEFINED	
 	if (cons_next != prod_tail) {		
 		prefetch(br->br_ring[cons_next]);