linux-kernel - [PATCH 3.2 020/185] can: c_can: Fix RX message handling, handle lost message before EOB

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Message-ID: <lsq.1388282923.597095294@decadent.org.uk>
Date:	Sun, 29 Dec 2013 03:08:43 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Marc Kleine-Budde" <mkl@...gutronix.de>,
	"Markus Pargmann" <mpa@...gutronix.de>
Subject: [PATCH 3.2 020/185] can: c_can: Fix RX message handling, handle
 lost message before EOB

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Markus Pargmann <mpa@...gutronix.de>

commit 5d0f801a2ccec3b1fdabc3392c8d99ed0413d216 upstream.

If we handle end of block messages with higher priority than a lost message,
we can run into an endless interrupt loop.

This is reproducable with a am335x processor and "cansequence -r" at 1Mbit.
As soon as we loose a packet we can't escape from an interrupt loop.

This patch fixes the problem by handling lost packets before EOB packets.

Signed-off-by: Markus Pargmann <mpa@...gutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/can/c_can/c_can.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -764,9 +764,6 @@ static int c_can_do_rx_poll(struct net_d
 			msg_ctrl_save = priv->read_reg(priv,
 					&priv->regs->ifregs[0].msg_cntrl);
 
-			if (msg_ctrl_save & IF_MCONT_EOB)
-				return num_rx_pkts;
-
 			if (msg_ctrl_save & IF_MCONT_MSGLST) {
 				c_can_handle_lost_msg_obj(dev, 0, msg_obj);
 				num_rx_pkts++;
@@ -774,6 +771,9 @@ static int c_can_do_rx_poll(struct net_d
 				continue;
 			}
 
+			if (msg_ctrl_save & IF_MCONT_EOB)
+				return num_rx_pkts;
+
 			if (!(msg_ctrl_save & IF_MCONT_NEWDAT))
 				continue;
 

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