linux-kernel - [137/262] can bcm: fix tx

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Date:	Wed, 09 Nov 2011 13:27:39 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Oliver Hartkopp <socketcan@...tkopp.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: [137/262] can bcm: fix tx_setup off-by-one errors

3.0-stable review patch.  If anyone has any objections, please let me know.

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


From: Oliver Hartkopp <socketcan@...tkopp.net>

[ Upstream commit aabdcb0b553b9c9547b1a506b34d55a764745870 ]

This patch fixes two off-by-one errors that canceled each other out.
Checking for the same condition two times in bcm_tx_timeout_tsklet() reduced
the count of frames to be sent by one. This did not show up the first time
tx_setup is invoked as an additional frame is sent due to TX_ANNONCE.
Invoking a second tx_setup on the same item led to a reduced (by 1) number of
sent frames.

Reported-by: Andre Naujoks <nautsch@...il.com>
Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 net/can/bcm.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -364,9 +364,6 @@ static void bcm_tx_timeout_tsklet(unsign
 
 			bcm_send_to_user(op, &msg_head, NULL, 0);
 		}
-	}
-
-	if (op->kt_ival1.tv64 && (op->count > 0)) {
 
 		/* send (next) frame */
 		bcm_can_tx(op);
@@ -969,8 +966,9 @@ static int bcm_tx_setup(struct bcm_msg_h
 		/* spec: send can_frame when starting timer */
 		op->flags |= TX_ANNOUNCE;
 
-		if (op->kt_ival1.tv64 && (op->count > 0)) {
-			/* op->count-- is done in bcm_tx_timeout_handler */
+		/* only start timer when having more frames than sent below */
+		if (op->kt_ival1.tv64 && (op->count > 1)) {
+			/* op->count-- is done in bcm_tx_timeout_tsklet */
 			hrtimer_start(&op->timer, op->kt_ival1,
 				      HRTIMER_MODE_REL);
 		} else
@@ -978,8 +976,11 @@ static int bcm_tx_setup(struct bcm_msg_h
 				      HRTIMER_MODE_REL);
 	}
 
-	if (op->flags & TX_ANNOUNCE)
+	if (op->flags & TX_ANNOUNCE) {
 		bcm_can_tx(op);
+		if (op->kt_ival1.tv64 && (op->count > 0))
+			op->count--;
+	}
 
 	return msg_head->nframes * CFSIZ + MHSIZ;
 }


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