Index: uipc_mbuf.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/uipc_mbuf.c,v
retrieving revision 1.143
diff -u -r1.143 uipc_mbuf.c
--- uipc_mbuf.c	24 Feb 2005 00:40:33 -0000	1.143
+++ uipc_mbuf.c	1 Mar 2005 19:27:24 -0000
@@ -234,9 +234,12 @@
 	 * This is tricky.  We need to make sure to decrement the
 	 * refcount in a safe way but to also clean up if we're the
 	 * last reference.  This method seems to do it without race.
+	 * The volatile cast is required to emit the proper load 
+	 * instructions. Otherwise gcc will optimize the read outside
+	 * of the while loop.
 	 */
 	while (dofree == 0) {
-		cnt = *(m->m_ext.ref_cnt);
+		cnt = *(volatile u_int *)(m->m_ext.ref_cnt);
 		if (atomic_cmpset_int(m->m_ext.ref_cnt, cnt, cnt - 1)) {
 			if (cnt == 1)
 				dofree = 1;