svn commit: r221565 - head/sys/dev/xl

[Pyun YongHyeon]

Author: yongari
Date: Fri May  6 23:49:10 2011
New Revision: 221565
URL: http://svn.freebsd.org/changeset/base/221565

Log:
  Reuse the TX descriptor(DPD) if xl_encap() failed instead of just
  picking the next available one. This may explain why xl(4) sees TX
  underrun error with no queued frame. I hope this addresses a long
  standing xl(4) watchdog timeout issue as well.
  
  Obtained from:	OpenBSD

Modified:
  head/sys/dev/xl/if_xl.c

Modified: head/sys/dev/xl/if_xl.c
==============================================================================
--- head/sys/dev/xl/if_xl.c	Fri May  6 23:01:29 2011	(r221564)
+++ head/sys/dev/xl/if_xl.c	Fri May  6 23:49:10 2011	(r221565)
@@ -2571,8 +2571,9 @@ static void
 xl_start_locked(struct ifnet *ifp)
 {
 	struct xl_softc		*sc = ifp->if_softc;
-	struct mbuf		*m_head = NULL;
+	struct mbuf		*m_head;
 	struct xl_chain		*prev = NULL, *cur_tx = NULL, *start_tx;
+	struct xl_chain		*prev_tx;
 	u_int32_t		status;
 	int			error;
 
@@ -2603,11 +2604,13 @@ xl_start_locked(struct ifnet *ifp)
 			break;
 
 		/* Pick a descriptor off the free list. */
+		prev_tx = cur_tx;
 		cur_tx = sc->xl_cdata.xl_tx_free;
 
 		/* Pack the data into the descriptor. */
 		error = xl_encap(sc, cur_tx, &m_head);
 		if (error) {
+			cur_tx = prev_tx;
 			if (m_head == NULL)
 				break;
 			ifp->if_drv_flags |= IFF_DRV_OACTIVE;
@@ -2702,8 +2705,9 @@ static void
 xl_start_90xB_locked(struct ifnet *ifp)
 {
 	struct xl_softc		*sc = ifp->if_softc;
-	struct mbuf		*m_head = NULL;
+	struct mbuf		*m_head;
 	struct xl_chain		*prev = NULL, *cur_tx = NULL, *start_tx;
+	struct xl_chain		*prev_tx;
 	int			error, idx;
 
 	XL_LOCK_ASSERT(sc);
@@ -2726,11 +2730,13 @@ xl_start_90xB_locked(struct ifnet *ifp)
 		if (m_head == NULL)
 			break;
 
+		prev_tx = cur_tx;
 		cur_tx = &sc->xl_cdata.xl_tx_chain[idx];
 
 		/* Pack the data into the descriptor. */
 		error = xl_encap(sc, cur_tx, &m_head);
 		if (error) {
+			cur_tx = prev_tx;
 			if (m_head == NULL)
 				break;
 			ifp->if_drv_flags |= IFF_DRV_OACTIVE;