linux-kernel - [PATCH 3.16 203/305] can: at91_can: RX queue could get stuck at high bus load

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Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Wolfgang Grandegger" <wg@...ndegger.com>,
	"Amr Bekhit" <amrbekhit@...il.com>,
	"Marc Kleine-Budde" <mkl@...gutronix.de>
Subject: [PATCH 3.16 203/305] can: at91_can: RX queue could get stuck at
 high bus load

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

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

From: Wolfgang Grandegger <wg@...ndegger.com>

commit 43200a4480cbbe660309621817f54cbb93907108 upstream.

At high bus load it could happen that "at91_poll()" enters with all RX
message boxes filled up. If then at the end the "quota" is exceeded as
well, "rx_next" will not be reset to the first RX mailbox and hence the
interrupts remain disabled.

Signed-off-by: Wolfgang Grandegger <wg@...ndegger.com>
Tested-by: Amr Bekhit <amrbekhit@...il.com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/can/at91_can.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/net/can/at91_can.c
+++ b/drivers/net/can/at91_can.c
@@ -734,9 +734,10 @@ static int at91_poll_rx(struct net_devic
 
 	/* upper group completed, look again in lower */
 	if (priv->rx_next > get_mb_rx_low_last(priv) &&
-	    quota > 0 && mb > get_mb_rx_last(priv)) {
+	    mb > get_mb_rx_last(priv)) {
 		priv->rx_next = get_mb_rx_first(priv);
-		goto again;
+		if (quota > 0)
+			goto again;
 	}
 
 	return received;