rework the start routines to avoid IF_PREPEND.

IF_PREPEND assumes the underlying send queue is priq, while hfsc may be
enabled on it.

the previous code pattern to DEQUEUE, try and encap the mbuf on the
ring, and if that failed cos there was no space it would PREPEND
it.

now it checks for space on the ring before it attempts to DEQUEUE.
failure to encap means the mbuf is now unconditionally dropped.

1 files changed, 14 insertions, 33 deletions

diff --git a/sys/dev/pci/if_jme.c b/sys/dev/pci/if_jme.c
index 3f2e36743a2..0aaf651e77d 100644
--- a/sys/dev/pci/if_jme.c
+++ b/sys/dev/pci/if_jme.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_jme.c,v 1.42 2015/10/25 13:04:28 mpi Exp $	*/
+/*	$OpenBSD: if_jme.c,v 1.43 2015/11/09 00:29:06 dlg Exp $	*/
 /*-
  * Copyright (c) 2008, Pyun YongHyeon <yongari@FreeBSD.org>
  * All rights reserved.
@@ -100,7 +100,7 @@ int	jme_init_rx_ring(struct jme_softc *);
 void	jme_init_tx_ring(struct jme_softc *);
 void	jme_init_ssb(struct jme_softc *);
 int	jme_newbuf(struct jme_softc *, struct jme_rxdesc *);
-int	jme_encap(struct jme_softc *, struct mbuf **);
+int	jme_encap(struct jme_softc *, struct mbuf *);
 void	jme_rxpkt(struct jme_softc *);
 
 void	jme_tick(void *);
@@ -1108,11 +1108,10 @@ jme_setwol(struct jme_softc *sc)
 #endif
 
 int
-jme_encap(struct jme_softc *sc, struct mbuf **m_head)
+jme_encap(struct jme_softc *sc, struct mbuf *m)
 {
 	struct jme_txdesc *txd;
 	struct jme_desc *desc;
-	struct mbuf *m;
 	int error, i, prod;
 	uint32_t cflags;
 
@@ -1120,32 +1119,20 @@ jme_encap(struct jme_softc *sc, struct mbuf **m_head)
 	txd = &sc->jme_cdata.jme_txdesc[prod];
 
 	error = bus_dmamap_load_mbuf(sc->sc_dmat, txd->tx_dmamap,
-				     *m_head, BUS_DMA_NOWAIT);
+	    m, BUS_DMA_NOWAIT);
 	if (error != 0 && error != EFBIG)
 		goto drop;
 	if (error != 0) {
-		if (m_defrag(*m_head, M_DONTWAIT)) {
+		if (m_defrag(m, M_DONTWAIT)) {
 			error = ENOBUFS;
 			goto drop;
 		}
 		error = bus_dmamap_load_mbuf(sc->sc_dmat, txd->tx_dmamap,
-					     *m_head, BUS_DMA_NOWAIT);
+					     m, BUS_DMA_NOWAIT);
 		if (error != 0)
 			goto drop;
 	}
 
-	/*
-	 * Check descriptor overrun. Leave one free descriptor.
-	 * Since we always use 64bit address mode for transmitting,
-	 * each Tx request requires one more dummy descriptor.
-	 */
-	if (sc->jme_cdata.jme_tx_cnt + txd->tx_dmamap->dm_nsegs + JME_TXD_RSVD >
-	    JME_TX_RING_CNT - JME_TXD_RSVD) {
-		bus_dmamap_unload(sc->sc_dmat, txd->tx_dmamap);
-		return (ENOBUFS);
-	}
-
-	m = *m_head;
 	cflags = 0;
 
 	/* Configure checksum offload. */
@@ -1204,8 +1191,7 @@ jme_encap(struct jme_softc *sc, struct mbuf **m_head)
 	return (0);
 
   drop:
-	m_freem(*m_head);
-	*m_head = NULL;
+	m_freem(m);
 	return (error);
 }
 
@@ -1213,7 +1199,7 @@ void
 jme_start(struct ifnet *ifp)
 {
 	struct jme_softc *sc = ifp->if_softc;
-	struct mbuf *m_head;
+	struct mbuf *m;
 	int enq = 0;
 
 	/* Reclaim transmitted frames. */
@@ -1238,8 +1224,8 @@ jme_start(struct ifnet *ifp)
 			break;
 		}
 
-		IFQ_DEQUEUE(&ifp->if_snd, m_head);
-		if (m_head == NULL)
+		IFQ_DEQUEUE(&ifp->if_snd, m);
+		if (m == NULL)
 			break;
 
 		/*
@@ -1247,14 +1233,9 @@ jme_start(struct ifnet *ifp)
 		 * don't have room, set the OACTIVE flag and wait
 		 * for the NIC to drain the ring.
 		 */
-		if (jme_encap(sc, &m_head)) {
-			if (m_head == NULL)
-				ifp->if_oerrors++;
-			else {
-				IF_PREPEND(&ifp->if_snd, m_head);
-				ifp->if_flags |= IFF_OACTIVE;
-			}
-			break;
+		if (jme_encap(sc, m) != 0) {
+			ifp->if_oerrors++;
+			continue;
 		}
 
 		enq++;
@@ -1265,7 +1246,7 @@ jme_start(struct ifnet *ifp)
 		 * to him.
 		 */
 		if (ifp->if_bpf != NULL)
-			bpf_mtap_ether(ifp->if_bpf, m_head, BPF_DIRECTION_OUT);
+			bpf_mtap_ether(ifp->if_bpf, m, BPF_DIRECTION_OUT);
 #endif
 	}