Add a transmit descriptor usage counter and use it to absolutely,

positively not let ti_encap() fill up the TX ring all the way and wrap
around. This fixes a potential transmit lockup where a really fast
machine (or particular TX traffic pattern) can overrun the end of the
ring.

Reported by: John Plevyak <jplevyak@inktomi.com>

2 files changed, 15 insertions, 4 deletions

diff --git a/sys/dev/ti/if_ti.c b/sys/dev/ti/if_ti.c
index 96370ed..a4af011 100644
--- a/sys/dev/ti/if_ti.c
+++ b/sys/dev/ti/if_ti.c
@@ -29,7 +29,7 @@
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  * THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id: if_ti.c,v 1.5 1999/05/09 17:07:00 peter Exp $
+ *	$Id: if_ti.c,v 1.6 1999/05/24 14:56:55 wpaul Exp $
  */
 
 /*
@@ -128,7 +128,7 @@
 
 #if !defined(lint)
 static const char rcsid[] =
-	"$Id: if_ti.c,v 1.5 1999/05/09 17:07:00 peter Exp $";
+	"$Id: if_ti.c,v 1.6 1999/05/24 14:56:55 wpaul Exp $";
 #endif
 
 /*
@@ -1065,6 +1065,7 @@ static void ti_free_tx_ring(sc)
 static int ti_init_tx_ring(sc)
 	struct ti_softc		*sc;
 {
+	sc->ti_txcnt = 0;
 	sc->ti_tx_saved_considx = 0;
 	CSR_WRITE_4(sc, TI_MB_SENDPROD_IDX, 0);
 	return(0);
@@ -1920,6 +1921,7 @@ static void ti_txeof(sc)
 			m_freem(sc->ti_cdata.ti_tx_chain[idx]);
 			sc->ti_cdata.ti_tx_chain[idx] = NULL;
 		}
+		sc->ti_txcnt--;
 		TI_INC(sc->ti_tx_saved_considx, TI_TX_RING_CNT);
 		ifp->if_timer = 0;
 	}
@@ -1996,7 +1998,7 @@ static int ti_encap(sc, m_head, txidx)
 {
 	struct ti_tx_desc	*f = NULL;
 	struct mbuf		*m;
-	u_int32_t		frag, cur;
+	u_int32_t		frag, cur, cnt = 0;
 #if NVLAN > 0
 	struct ifvlan		*ifv = NULL;
 
@@ -2045,8 +2047,15 @@ static int ti_encap(sc, m_head, txidx)
 				f->ti_vlan_tag = 0;
 			}
 #endif
+			/*
+			 * Sanity check: avoid coming within 16 descriptors
+			 * of the end of the ring.
+			 */
+			if ((TI_TX_RING_CNT - (sc->ti_txcnt + cnt)) < 16)
+				return(ENOBUFS);
 			cur = frag;
 			TI_INC(frag, TI_TX_RING_CNT);
+			cnt++;
 		}
 	}
 
@@ -2062,6 +2071,7 @@ static int ti_encap(sc, m_head, txidx)
 	else
 		sc->ti_rdata->ti_tx_ring[cur].ti_flags |= TI_BDFLAG_END;
 	sc->ti_cdata.ti_tx_chain[cur] = m_head;
+	sc->ti_txcnt += cnt;
 
 	*txidx = frag;
 
diff --git a/sys/dev/ti/if_tireg.h b/sys/dev/ti/if_tireg.h
index 666c039..c79336a 100644
--- a/sys/dev/ti/if_tireg.h
+++ b/sys/dev/ti/if_tireg.h
@@ -29,7 +29,7 @@
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  * THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id: if_tireg.h,v 1.2 1999/05/03 17:44:52 wpaul Exp $
+ *	$Id: if_tireg.h,v 1.3 1999/05/26 23:01:50 gallatin Exp $
  */
 
 /*
@@ -1151,6 +1151,7 @@ struct ti_softc {
 	u_int32_t		ti_tx_max_coal_bds;
 	u_int32_t		ti_tx_buf_ratio;
 	int			ti_if_flags;
+	int			ti_txcnt;
 };
 
 /*