--- /usr/src/sys/kern/vfs_default.c	Fri Aug 19 19:36:51 2005
+++ src/sys/kern/vfs_default.c	Sat Sep  3 01:36:57 2005
@@ -41,6 +41,7 @@
 #include <sys/buf.h>
 #include <sys/conf.h>
 #include <sys/event.h>
+#include <sys/kdb.h>
 #include <sys/kernel.h>
 #include <sys/limits.h>
 #include <sys/lock.h>
@@ -259,8 +260,19 @@
 	} */ *ap;
 {
 	struct vnode *vp = ap->a_vp;
+	int flags = ap->a_flags;
+	int error;
 
-	return (lockmgr(vp->v_vnlock, ap->a_flags, VI_MTX(vp), ap->a_td));
+	if ((flags & LK_INTERLOCK) == 0)
+		VI_LOCK(vp);
+	if ((vp->v_iflag & VI_DOOMED) != 0 &&
+	    vp->v_vnlock->lk_lockholder != ap->a_td) {
+		printf("Thread %p trying to lock doomed vnode\n", ap->a_td);
+		kdb_backtrace();
+	}
+	error = lockmgr(vp->v_vnlock, ap->a_flags | LK_INTERLOCK, VI_MTX(vp),
+	    ap->a_td);
+	return (error);
 }
 
 /* See above. */