I finally managed to re-produce an affect similar to Jason's case. It
may not be the exact same issue, but it is a serious problem and must
be addressed.
1. Push out packet on em/igb with high rate.
2. Disconnect cable and wait for a few seconds. "netstat -ind" shows that
Drops are increasing.
3. Re-connect the cable. Both sides of like re-negotiate and the links comes up.
4. But ..., no packets is ever transmitted again and Drops still increasing!
This is because em/lem/igb and some other interfaces (i.e., bce) have
a check at the very beginning of their _start function
which checks link status and immediately returns if it is inactive.
This behavior causes if_snd to fills up in step 2 and when this happens,
IFQ_HANDOFF never calls if_start again, even when the link becomes
active again.
A cable unplug is not necessary to trigger the issue. Any temporary
link loss (e.i., during re-negotiation) can potentially lead to
aforementioned problem.
IMHO, this is not a driver issue and the real fix would be to change
IFQ_HANDOFF to call if_start when the queue is full.
Jason, If you are interested, I can prepare a patch for you
to address this issue in if_em and see if it helps.
--- if_em.c.orig 2011-10-27 21:09:33.000000000 +0330
+++ if_em.c 2011-10-27 21:46:18.000000000 +0330
@@ -85,6 +85,14 @@
#include "e1000_82571.h"
#include "if_em.h"
+#if !defined(DISABLE_FIXUPS) && __FreeBSD_version < 800000
+static __inline int
+pci_find_cap(device_t dev, int capability, int *capreg)
+{
+ return (PCI_FIND_EXTCAP(device_get_parent(dev), dev, capability,
capreg));
+}
+#endif
+
/*********************************************************************
* Set this to one to display debug statistics
*********************************************************************/
@@ -399,6 +407,12 @@
/* Global used in WOL setup with multiport cards */
static int global_quad_port_a = 0;
+#ifndef DISABLE_FIXUPS
+static int em_rx_hang_fixup = 0;
+SYSCTL_INT(_hw_em, OID_AUTO, rx_hang_fixup, CTLFLAG_RW, &em_rx_hang_fixup, 0,
+ "Enable/disable r1.69 RX hang fixup code");
+#endif
+
/*********************************************************************
* Device identification routine
*
@@ -864,7 +878,11 @@
int err = 0, enq = 0;
if ((ifp->if_drv_flags & (IFF_DRV_RUNNING | IFF_DRV_OACTIVE)) !=
+#ifdef DISABLE_FIXUPS
IFF_DRV_RUNNING || adapter->link_active == 0) {
+#else
+ IFF_DRV_RUNNING) {
+#endif
if (m != NULL)
err = drbr_enqueue(ifp, txr->br, m);
return (err);
@@ -963,8 +981,10 @@
IFF_DRV_RUNNING)
return;
+#ifdef DISABLE_FIXUPS
if (!adapter->link_active)
return;
+#endif
while (!IFQ_DRV_IS_EMPTY(&ifp->if_snd)) {
/* Call cleanup if number of TX descriptors low */
@@ -1414,7 +1434,11 @@
* Legacy polling routine: note this only works with single queue
*
*********************************************************************/
+#if !defined(DISABLE_FIXUPS) && __FreeBSD_version < 800000
+static void
+#else
static int
+#endif
em_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
{
struct adapter *adapter = ifp->if_softc;
@@ -1426,7 +1450,11 @@
EM_CORE_LOCK(adapter);
if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
EM_CORE_UNLOCK(adapter);
+#if !defined(DISABLE_FIXUPS) && __FreeBSD_version < 800000
+ return;
+#else
return (0);
+#endif
}
if (cmd == POLL_AND_CHECK_STATUS) {
@@ -1452,8 +1480,11 @@
em_start_locked(ifp, txr);
#endif
EM_TX_UNLOCK(txr);
-
+#if !defined(DISABLE_FIXUPS) && __FreeBSD_version < 800000
+ return;
+#else
return (rx_done);
+#endif
}
#endif /* DEVICE_POLLING */
@@ -2213,6 +2244,16 @@
e1000_get_laa_state_82571(&adapter->hw))
e1000_rar_set(&adapter->hw, adapter->hw.mac.addr, 0);
+#ifndef DISABLE_FIXUPS
+ if (em_rx_hang_fixup) {
+ /* trigger tq to refill rx ring queue if it is empty */
+ for (int i = 0; i < adapter->num_queues; i++, rxr++) {
+ if (rxr->next_to_check == rxr->next_to_refresh) {
+ taskqueue_enqueue(rxr->tq, &rxr->rx_task);
+ }
+ }
+ }
+#endif
/* Mask to use in the irq trigger */
if (adapter->msix_mem)
trigger = rxr->ims; /* RX for 82574 */
@@ -3766,7 +3807,7 @@
* If we have a minimum free, clear IFF_DRV_OACTIVE
* to tell the stack that it is OK to send packets.
*/
- if (txr->tx_avail > EM_MAX_SCATTER)
+ if (txr->tx_avail >= EM_MAX_SCATTER)
ifp->if_drv_flags &= ~IFF_DRV_OACTIVE;
/* Disable watchdog if all clean */
@@ -5553,4 +5594,8 @@
rxr->rx_discarded);
device_printf(dev, "RX Next to Check = %d\n", rxr->next_to_check);
device_printf(dev, "RX Next to Refresh = %d\n", rxr->next_to_refresh);
+#ifndef DISABLE_FIXUPS
+ device_printf(dev, "Link state: %s\n",
+ adapter->link_active? "active": "inactive");
+#endif
}
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