[ 3.5.y.z extended stable ] Patch "sfc: Detach net device when stopping queues for" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Mon Mar 25 18:03:48 UTC 2013

This is a note to let you know that I have just added a patch titled

    sfc: Detach net device when stopping queues for

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From 81b8aefbd796facbfe8e2f8578c5eece85575ecb Mon Sep 17 00:00:00 2001
From: Ben Hutchings <bhutchings at solarflare.com>
Date: Mon, 28 Jan 2013 19:01:06 +0000
Subject: [PATCH] sfc: Detach net device when stopping queues for

commit 29c69a4882641285a854d6d03ca5adbba68c0034 upstream.

We must only ever stop TX queues when they are full or the net device
is not 'ready' so far as the net core, and specifically the watchdog,
is concerned.  Otherwise, the watchdog may fire *immediately* if no
packets have been added to the queue in the last 5 seconds.

The device is ready if all the following are true:

(a) It has a qdisc
(b) It is marked present
(c) It is running
(d) The link is reported up

(a) and (c) are normally true, and must not be changed by a driver.
(d) is under our control, but fake link changes may disturb userland.
This leaves (b).  We already mark the device absent during reset
and self-test, but we need to do the same during MTU changes and ring
reallocation.  We don't need to do this when the device is brought
down because then (c) is already false.

Signed-off-by: Ben Hutchings <bhutchings at solarflare.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/net/ethernet/sfc/efx.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 3d49f44..5fe7b35 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -754,6 +754,7 @@ efx_realloc_channels(struct efx_nic *efx, u32 rxq_entries, u32 txq_entries)

+	efx_device_detach_sync(efx);
 	efx_stop_interrupts(efx, true);

@@ -807,6 +808,7 @@ out:

 	efx_start_interrupts(efx, true);
+	netif_device_attach(efx->net_dev);
 	return rc;

@@ -1601,8 +1603,12 @@ static void efx_stop_all(struct efx_nic *efx)
 	/* Flush efx_mac_work(), refill_workqueue, monitor_work */

-	/* Stop the kernel transmit interface late, so the watchdog
-	 * timer isn't ticking over the flush */
+	/* Stop the kernel transmit interface.  This is only valid if
+	 * the device is stopped or detached; otherwise the watchdog
+	 * may fire immediately.
+	 */
+	WARN_ON(netif_running(efx->net_dev) &&
+		netif_device_present(efx->net_dev));

@@ -1921,10 +1927,11 @@ static int efx_change_mtu(struct net_device *net_dev, int new_mtu)
 	if (new_mtu > EFX_MAX_MTU)
 		return -EINVAL;

-	efx_stop_all(efx);
 	netif_dbg(efx, drv, efx->net_dev, "changing MTU to %d\n", new_mtu);

+	efx_device_detach_sync(efx);
+	efx_stop_all(efx);
 	/* Reconfigure the MAC before enabling the dma queues so that
 	 * the RX buffers don't overflow */
@@ -1933,6 +1940,7 @@ static int efx_change_mtu(struct net_device *net_dev, int new_mtu)

+	netif_device_attach(efx->net_dev);
 	return 0;


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