--- //depot/vendor/freebsd/src/sys/dev/twe/twe.c	2012-08-13 21:30:34.000000000 0000
+++ //depot/user/jhb/cleanup/sys/dev/twe/twe.c	2012-08-14 13:58:43.000000000 0000
@@ -410,6 +410,9 @@
 	return;
 
     /* spin until something prevents us from doing any work */
+    KASSERT(!(sc->twe_state & TWE_STATE_IN_STARTIO),
+	("nested call to twe_startio()"));
+    sc->twe_state |= TWE_STATE_IN_STARTIO;
     for (;;) {
 
 	/* try to get a command that's already ready to go */
@@ -470,6 +473,7 @@
 		wakeup_one(tr); /* wakeup the sleeping owner */
 	}
     }
+    sc->twe_state &= ~TWE_STATE_IN_STARTIO;
 }
 
 /********************************************************************************
@@ -1104,7 +1108,7 @@
 {
     struct twe_softc	*sc = tr->tr_sc;
     TWE_Command		*cmd;
-    int			i;
+    int			first, i;
     u_int32_t		status_reg;
 
     debug_called(4);
@@ -1122,6 +1126,7 @@
      * XXX it might be more efficient to return EBUSY immediately
      *     and let the command be rescheduled.
      */
+    first = 1;
     for (i = 100000; (i > 0); i--) {
 	
 	/* check to see if we can post a command */
@@ -1129,6 +1134,8 @@
 	twe_check_bits(sc, status_reg);
 
 	if (!(status_reg & TWE_STATUS_COMMAND_QUEUE_FULL)) {
+	    if (!first)
+		sc->twe_spincompl++;
 	    twe_enqueue_busy(tr);
 
 	    TWE_COMMAND_QUEUE(sc, TWE_FIND_COMMANDPHYS(tr));
@@ -1144,6 +1151,11 @@
 	    }
 #endif
 	    return(0);
+	} else if (!(status_reg & TWE_STATUS_RESPONSE_QUEUE_EMPTY))
+	    twe_done(sc);
+	if (first) {
+	    sc->twe_spinwaits++;
+	    first = 0;
 	}
     }
 
@@ -1180,6 +1192,8 @@
 
 	if (!(status_reg & TWE_STATUS_RESPONSE_QUEUE_EMPTY)) {
 	    found = 1;
+	    if (sc->twe_state & TWE_STATE_IN_STARTIO)
+		sc->twe_spindone++;
 	    rq = TWE_RESPONSE_QUEUE(sc);
 	    tr = sc->twe_lookup[rq.u.response_id];	/* find command */
 	    cmd = TWE_FIND_COMMAND(tr);
@@ -1198,7 +1212,7 @@
     }
 
     /* if we've completed any commands, try posting some more */
-    if (found)
+    if (found && !(sc->twe_state & TWE_STATE_IN_STARTIO))
 	twe_startio(sc);
 
     /* handle completion and timeouts */
@@ -1768,7 +1782,6 @@
 static char *
 twe_format_aen(struct twe_softc *sc, u_int16_t aen)
 {
-    static char	buf[80];
     device_t	child;
     char	*code, *msg;
 
@@ -1785,25 +1798,28 @@
 
     case 'c':
 	if ((child = sc->twe_drive[TWE_AEN_UNIT(aen)].td_disk) != NULL) {
-	    sprintf(buf, "twed%d: %s", device_get_unit(child), msg);
+	    snprintf(sc->twe_aen_buf, sizeof(sc->twe_aen_buf), "twed%d: %s",
+		device_get_unit(child), msg);
 	} else {
-	    sprintf(buf, "twe%d: %s for unknown unit %d", device_get_unit(sc->twe_dev),
-		    msg, TWE_AEN_UNIT(aen));
+	    snprintf(sc->twe_aen_buf, sizeof(sc->twe_aen_buf),
+		"twe%d: %s for unknown unit %d", device_get_unit(sc->twe_dev),
+		msg, TWE_AEN_UNIT(aen));
 	}
-	return(buf);
+	return(sc->twe_aen_buf);
 
     case 'p':
-	sprintf(buf, "twe%d: port %d: %s", device_get_unit(sc->twe_dev), TWE_AEN_UNIT(aen),
-		msg);
-	return(buf);
+	snprintf(sc->twe_aen_buf, sizeof(sc->twe_aen_buf),
+	    "twe%d: port %d: %s", device_get_unit(sc->twe_dev),
+	    TWE_AEN_UNIT(aen), msg);
+	return(sc->twe_aen_buf);
 
 	
     case 'x':
     default:
 	break;
     }
-    sprintf(buf, "unknown AEN 0x%x", aen);
-    return(buf);
+    snprintf(sc->twe_aen_buf, sizeof(sc->twe_aen_buf), "unknown AEN 0x%x", aen);
+    return(sc->twe_aen_buf);
 }
 
 /********************************************************************************
--- //depot/vendor/freebsd/src/sys/dev/twe/twe_freebsd.c	2012-08-13 21:30:34.000000000 0000
+++ //depot/user/jhb/cleanup/sys/dev/twe/twe_freebsd.c	2012-08-14 13:56:54.000000000 0000
@@ -179,7 +179,7 @@
 twe_attach(device_t dev)
 {
     struct twe_softc	*sc;
-    struct sysctl_oid	*sysctl_tree;
+    struct sysctl_oid	*sysctl_tree, *spin_tree;
     int			rid, error;
 
     debug_called(4);
@@ -209,6 +209,19 @@
 	OID_AUTO, "driver_version", CTLFLAG_RD, TWE_DRIVER_VERSION_STRING, 0,
 	"TWE driver version");
 
+    spin_tree = SYSCTL_ADD_NODE(device_get_sysctl_ctx(dev),
+	SYSCTL_CHILDREN(sysctl_tree), OID_AUTO, "spin", CTLFLAG_RD, 0,
+	"twe_start() spin statistics");
+    SYSCTL_ADD_INT(device_get_sysctl_ctx(dev), SYSCTL_CHILDREN(spin_tree),
+	OID_AUTO, "waits", CTLFLAG_RD, &sc->twe_spinwaits, 0,
+	"Commands that encountered a busy command queue and had to wait");
+    SYSCTL_ADD_INT(device_get_sysctl_ctx(dev), SYSCTL_CHILDREN(spin_tree),
+	OID_AUTO, "compl", CTLFLAG_RD, &sc->twe_spincompl, 0,
+	"Commands that eventually completed after having to wait");
+    SYSCTL_ADD_INT(device_get_sysctl_ctx(dev), SYSCTL_CHILDREN(spin_tree),
+	OID_AUTO, "done", CTLFLAG_RD, &sc->twe_spinwaits, 0,
+	"Commands completed while waiting to enqueue another command");
+    
     /*
      * Force the busmaster enable bit on, in case the BIOS forgot.
      */
--- //depot/vendor/freebsd/src/sys/dev/twe/twevar.h	2012-08-13 21:30:34.000000000 0000
+++ //depot/user/jhb/cleanup/sys/dev/twe/twevar.h	2012-08-14 13:56:54.000000000 0000
@@ -125,6 +125,7 @@
     u_int16_t		twe_aen_queue[TWE_Q_LENGTH];	/* AENs queued for userland tool(s) */
     int			twe_aen_head, twe_aen_tail;	/* ringbuffer pointers for AEN queue */
     int			twe_wait_aen;    		/* wait-for-aen notification */
+    char		twe_aen_buf[80];		/* AEN format buffer */
 
     /* controller status */
     int			twe_state;
@@ -135,8 +136,13 @@
 #define TWE_STATE_FRZN		(1<<4)	/* got EINPROGRESS */
 #define TWE_STATE_CTLR_BUSY	(1<<5)	/* controller cmd queue full */
 #define	TWE_STATE_DETACHING	(1<<6)	/* controller is being shut down */
+#define	TWE_STATE_IN_STARTIO	(1<<7)	/* prevent twe_startio() recursion */
+
     int			twe_host_id;
     struct twe_qstat	twe_qstat[TWEQ_COUNT];	/* queue statistics */
+    int			twe_spinwaits;
+    int			twe_spincompl;
+    int			twe_spindone;
 
     TWE_PLATFORM_SOFTC		/* platform-specific softc elements */
 };