commit 80f9ba69ca3e78fe8c1597db39337d7be59e4b04
Author: Ryota Ozaki <ozaki-r@iij.ad.jp>
Date:   Fri Jan 20 09:57:50 2017 +0900

    Tx softint

diff --git a/sys/dev/usb/if_axe.c b/sys/dev/usb/if_axe.c
index a808268..30361c3 100644
--- a/sys/dev/usb/if_axe.c
+++ b/sys/dev/usb/if_axe.c
@@ -990,6 +990,7 @@ axe_attach(device_t parent, device_t self, void *aux)
 	ifp->if_softc = sc;
 	strlcpy(ifp->if_xname, devname, IFNAMSIZ);
 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
+	ifp->if_extflags = IFEF_TX_SOFTINT;
 	ifp->if_ioctl = axe_ioctl;
 	ifp->if_start = axe_start;
 	ifp->if_init = axe_init;
@@ -1044,6 +1045,7 @@ axe_attach(device_t parent, device_t self, void *aux)
 
 	/* Attach the interface. */
 	if_attach(ifp);
+	if_deferred_start_init(ifp, NULL);
 	ether_ifattach(ifp, sc->axe_enaddr);
 	rnd_attach_source(&sc->rnd_source, device_xname(sc->axe_dev),
 	    RND_TYPE_NET, RND_FLAG_DEFAULT);
diff --git a/sys/net/if.c b/sys/net/if.c
index f2db4ed..6638712 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -3194,8 +3194,12 @@ if_transmit(struct ifnet *ifp, struct mbuf *m)
 	if (m->m_flags & M_MCAST)
 		ifp->if_omcasts++;
 
-	if ((ifp->if_flags & IFF_OACTIVE) == 0)
-		if_start_lock(ifp);
+	if ((ifp->if_flags & IFF_OACTIVE) == 0) {
+		if (ISSET(ifp->if_extflags, IFEF_TX_SOFTINT))
+			if_schedule_deferred_start(ifp);
+		else
+			if_start_lock(ifp);
+	}
 out:
 	splx(s);
 
diff --git a/sys/net/if.h b/sys/net/if.h
index 837b97e..ba79650 100644
--- a/sys/net/if.h
+++ b/sys/net/if.h
@@ -387,6 +387,7 @@ typedef struct ifnet {
 #define	IFEF_OUTPUT_MPSAFE		__BIT(0)	/* if_output() can run parallel */
 #define	IFEF_START_MPSAFE		__BIT(1)	/* if_start() can run parallel */
 #define	IFEF_NO_LINK_STATE_CHANGE	__BIT(2)	/* doesn't use link state interrupts */
+#define	IFEF_TX_SOFTINT			__BIT(3)	/* defer transmit to softint */
 
 #ifdef _KERNEL
 static inline bool