Apply the same netisr mechanism to transmissions as well. In order to

drive the transmitter, we have to check the interface's send queue in the
TX end of frame handler (i.e. the usb bulk out callback) and push out new
transmissions if the queue has packets in it and the transmitter is
ready. But the txeof handler is also called from a USB callback running
at splusb() too.

Grrr.

sys/dev/usb/if_aue.c

@@ -1024,8 +1024,7 @@ static void aue_txeof(xfer, priv, status)
 	else
 		ifp->if_opackets++;
 
-	if (ifp->if_snd.ifq_head != NULL)
-		aue_start(ifp);
+	usb_tx_done(ifp);
 
 	splx(s);
 

sys/dev/usb/if_kue.c

@@ -668,7 +668,7 @@ static void kue_rxeof(xfer, priv, status)
 
 	usbd_get_xfer_status(xfer, NULL, NULL, &total_len, NULL);
 	m = c->kue_mbuf;
-	if (total_len == 1)
+	if (total_len <= 1)
 		goto done;
 
 	len = *mtod(m, u_int16_t *);
@@ -763,8 +763,7 @@ static void kue_txeof(xfer, priv, status)
 	else
 		ifp->if_opackets++;
 
-	if (ifp->if_snd.ifq_head != NULL)
-		kue_start(ifp);
+	usb_tx_done(ifp);
 
 	splx(s);
 

sys/dev/usb/usb_ethersubr.c

@@ -55,6 +55,7 @@
 #include <sys/sockio.h>
 #include <sys/mbuf.h>
 #include <sys/kernel.h>
+#include <sys/malloc.h>
 #include <sys/socket.h>
 
 #include <net/if.h>
@@ -63,6 +64,7 @@
 #include <net/ethernet.h>
 #include <net/netisr.h>
 
+#include <dev/usb/usb.h>
 #include <dev/usb/usb_ethersubr.h>
 
 #ifndef lint
@@ -71,6 +73,12 @@ static const char rcsid[] =
 #endif
 
 static struct ifqueue usbq;
+struct usb_ifent {
+	struct ifnet		*ifp;
+	LIST_ENTRY(usb_ifent)	list;
+};
+static LIST_HEAD(, usb_ifent) usb_iflisthead;
+static int usb_inited = 0;
 
 static void usbintr		__P((void));
 
@@ -78,17 +86,33 @@ static void usbintr()
 {
 	struct ether_header	*eh;
 	struct mbuf		*m;
+	struct ifnet		*ifp;
+	struct usb_ifent	*e;
 	int			s;
 
 	s = splimp();
 
+	/* Check the RX queue */
 	while(1) {
 		IF_DEQUEUE(&usbq, m);
 		if (m == NULL)
 			break;
 		eh = mtod(m, struct ether_header *);
 		m_adj(m, sizeof(struct ether_header));
-		ether_input(m->m_pkthdr.rcvif, eh, m);
+		ifp = m->m_pkthdr.rcvif;
+		ether_input(ifp, eh, m);
+		if (ifp->if_snd.ifq_head != NULL)
+			(*ifp->if_start)(ifp);
+	}
+
+	/* Check the TX queue */
+	while (usb_iflisthead.lh_first != NULL) {
+		e = usb_iflisthead.lh_first;
+		ifp = e->ifp;
+		if (ifp->if_snd.ifq_head != NULL)
+			(*ifp->if_start)(ifp);
+		LIST_REMOVE(e, list);
+		free(e, M_USBDEV);
 	}
 
 	splx(s);
@@ -98,7 +122,12 @@ static void usbintr()
 
 void usb_register_netisr()
 {
-	register_netisr(NETISR_USB, usbintr);
+	if (usb_inited == 0) {
+		register_netisr(NETISR_USB, usbintr);
+		LIST_INIT(&usb_iflisthead);
+		usb_inited++;
+	}
+
 	return;
 }
 
@@ -116,3 +145,26 @@ void usb_ether_input(m)
 	splx(s);
 	return;
 }
+
+void usb_tx_done(ifp)
+	struct ifnet		*ifp;
+{
+	struct usb_ifent	*e;
+
+	/* See if this if is already scheduled. */
+	for (e = usb_iflisthead.lh_first; e != NULL; e = e->list.le_next) {
+		if (ifp == e->ifp)
+			return;
+	}
+		
+	e = malloc(sizeof(struct usb_ifent), M_USB, M_NOWAIT);
+	if (e == NULL)
+		return;
+
+	e->ifp = ifp;
+
+	LIST_INSERT_HEAD(&usb_iflisthead, e, list);
+	schednetisr(NETISR_USB);
+
+	return;
+}

sys/dev/usb/usb_ethersubr.h

@@ -41,5 +41,6 @@
 
 void usb_register_netisr	__P((void));
 void usb_ether_input		__P((struct mbuf *));
+void usb_tx_done		__P((struct ifnet *));
 
 #endif