Had a discussion about this with David Holland and finally he suggested
avoiding links to procfs itself.  This shouldn't hurt any real uses
and makes the panics go away once again.  As a bonus, it's a totally
procfs-contained approach.

Index: procfs_vnops.c
===================================================================
RCS file: /cvsroot/src/sys/miscfs/procfs/procfs_vnops.c,v
retrieving revision 1.157
diff -p -u -p -r1.157 procfs_vnops.c
--- procfs_vnops.c	24 May 2007 00:37:41 -0000	1.157
+++ procfs_vnops.c	21 Jul 2007 23:30:03 -0000
@@ -584,6 +584,18 @@ procfs_dir(pfstype t, struct lwp *caller
 		return (NULL);
 	}
 
+	/*
+	 * XXX: this horrible kludge avoids locking panics when
+	 * attempting to lookup links that point to within procfs
+	 */
+	if (vp != NULL && vp->v_tag == VT_PROCFS) {
+		if (bpp) {
+			*--bp = '/';
+			*bpp = bp;
+		}
+		return vp;
+	}
+
 	if (rvp == NULL)
 		rvp = rootvnode;
 	mutex_exit(&target->p_mutex);	/* XXXSMP */
@@ -1590,11 +1602,20 @@ procfs_readlink(v)
 			}
 			bp = path + MAXPATHLEN;
 			*--bp = '\0';
-			vp = curproc->p_cwdi->cwdi_rdir;	/* XXXSMP */
-			if (vp == NULL)
-				vp = rootvnode;
-			error = getcwd_common(vxp, vp, &bp, path,
-			    MAXPATHLEN / 2, 0, curlwp);
+
+			/*
+			 * XXX: kludge to avoid locking against ourselves
+			 * in getcwd()
+			 */
+			if (vxp->v_tag == VT_PROCFS) {
+				*--bp = '/';
+			} else {
+				vp = curproc->p_cwdi->cwdi_rdir; /* XXXSMP */
+				if (vp == NULL)
+					vp = rootvnode;
+				error = getcwd_common(vxp, vp, &bp, path,
+				    MAXPATHLEN / 2, 0, curlwp);
+			}
 			FILE_UNUSE(fp, curlwp);
 			if (error)
 				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"