netdev - [PATCH] net/fec: Don't let ndo_start_xmit return NETDEV_TX

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Message-Id: <1375176580-7368-1-git-send-email-u.kleine-koenig@pengutronix.de>
Date:	Tue, 30 Jul 2013 11:29:40 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	netdev@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Frank Li <Frank.Li@...escale.com>,
	Shawn Guo <shawn.guo@...aro.org>, kernel@...gutronix.de,
	Hector Palacios <hector.palacios@...i.com>,
	Tim Sander <tim.sander@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Duan Fugang-B38611 <B38611@...escale.com>,
	Florian Fainelli <florian@...nwrt.org>,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: [PATCH] net/fec: Don't let ndo_start_xmit return NETDEV_TX_BUSY without link

Don't test for having link and let hardware deal with this situation.

Without this patch I see a machine running an -rt patched Linux being
stuck in sch_direct_xmit when it looses link while there is still a
packet to be sent. In this case the fec_enet_start_xmit routine returned
NETDEV_TX_BUSY which makes the network stack reschedule the packet and
so sch_direct_xmit calls fec_enet_start_xmit again.
I failed to reproduce a complete hang without -rt, but I think the
problem exists there, too.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
Hello,

this is a new variant of "[PATCH] net/fec: call netif_carrier_off when
not having link" that drops calling netif_carrier_{on,off} in
fec_restart because the phy library already handles that.

I think this is 3.11 material assuming you are ok with the patch now.

Best regards
Uwe

 drivers/net/ethernet/freescale/fec_main.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index ed61160..792d729 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -280,11 +280,6 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	unsigned short	status;
 	unsigned int index;

-	if (!fep->link) {
-		/* Link is down or auto-negotiation is in progress. */
-		return NETDEV_TX_BUSY;
-	}
-
 	/* Fill in a Tx ring entry */
 	bdp = fep->cur_tx;

-- 
1.8.3.2

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