Here's a shotgun-approach that makes the panic go away.  I really didn't
think it through as to if it produces more problems than it solves.

Index: kern/vfs_getcwd.c
===================================================================
RCS file: /cvsroot/src/sys/kern/vfs_getcwd.c,v
retrieving revision 1.35
diff -p -u -r1.35 vfs_getcwd.c
--- kern/vfs_getcwd.c	9 Feb 2007 21:55:32 -0000	1.35
+++ kern/vfs_getcwd.c	20 Jul 2007 15:42:27 -0000
@@ -258,7 +258,7 @@ unionread:
 		vput(tvp);
 		VREF(uvp);
 		*uvpp = uvp;
-		vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY);
+		vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 		goto unionread;
 	}
 #endif
@@ -315,7 +315,7 @@ getcwd_getcache(struct vnode **lvpp, str
 	 */
 
 	VOP_UNLOCK(lvp, 0);
-	error = vget(uvp, LK_EXCLUSIVE | LK_RETRY);
+	error = vget(uvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 
 	/*
 	 * Verify that vget succeeded while we were waiting for the
@@ -329,7 +329,7 @@ getcwd_getcache(struct vnode **lvpp, str
 		 * the hard way.
 		 */
 		*uvpp = NULL;
-		vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
+		vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 		*bpp = obp;
 		return -1;
 	}
@@ -371,7 +371,7 @@ getcwd_common(struct vnode *lvp, struct 
 	 *	uvp is either NULL, or locked and held.
 	 */
 
-	vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
+	vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 	if (bufp)
 		bp = *bpp;
 
@@ -418,7 +418,7 @@ getcwd_common(struct vnode *lvp, struct 
 				goto out;
 			}
 			VREF(lvp);
-			error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
+			error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 			if (error != 0) {
 				vrele(lvp);
 				lvp = NULL;
Index: miscfs/procfs/procfs_vnops.c
===================================================================
RCS file: /cvsroot/src/sys/miscfs/procfs/procfs_vnops.c,v
retrieving revision 1.157
diff -p -u -r1.157 procfs_vnops.c
--- miscfs/procfs/procfs_vnops.c	24 May 2007 00:37:41 -0000	1.157
+++ miscfs/procfs/procfs_vnops.c	20 Jul 2007 15:42:27 -0000
@@ -1062,7 +1062,7 @@ procfs_lookup(v)
 		if (cnp->cn_flags & ISDOTDOT) {
 			VOP_UNLOCK(dvp, 0);
 			error = procfs_root(dvp->v_mount, vpp);
-			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
+			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 			return (error);
 		}
 
@@ -1093,7 +1093,7 @@ procfs_lookup(v)
 			fvp = p->p_textvp;
 			/* We already checked that it exists. */
 			VREF(fvp);
-			vn_lock(fvp, LK_EXCLUSIVE | LK_RETRY);
+			vn_lock(fvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 			*vpp = fvp;
 			procfs_proc_unlock(p);
 			return (0);
@@ -1120,7 +1120,7 @@ procfs_lookup(v)
 			VOP_UNLOCK(dvp, 0);
 			error = procfs_allocvp(dvp->v_mount, vpp, pfs->pfs_pid,
 			    PFSproc, -1, p);
-			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
+			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 			procfs_proc_unlock(p);
 			return (error);
 		}
@@ -1146,8 +1146,7 @@ procfs_lookup(v)
 
 			VREF(fvp);
 			FILE_UNUSE(fp, l);
-			vn_lock(fvp, LK_EXCLUSIVE | LK_RETRY |
-			    (p == curproc ? LK_CANRECURSE : 0));
+			vn_lock(fvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
 			*vpp = fvp;
 			error = 0;
 			break;

-- 
Antti Kantee <pooka@iki.fi>                     Of course he runs NetBSD
http://www.iki.fi/pooka/                          http://www.NetBSD.org/
    "la qualité la plus indispensable du cuisinier est l'exactitude"