From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <avorontsov@dev.rtsoft.ru>
Received: from mail.dev.rtsoft.ru (mail.dev.rtsoft.ru [213.79.90.226])
	by ozlabs.org (Postfix) with SMTP id C69ECB6ED0
	for <linuxppc-dev@ozlabs.org>; Mon, 11 Jan 2010 21:52:50 +1100 (EST)
Date: Mon, 11 Jan 2010 13:52:48 +0300
From: Anton Vorontsov <avorontsov@ru.mvista.com>
To: Wu Jiajun-B06378 <B06378@freescale.com>
Subject: Re: [PATCH 1/3] ucc_geth: Fix empty TX queue processing
Message-ID: <20100111105248.GA28580@oksana.dev.rtsoft.ru>
References: <0A1FE637C2C7E148B9573BB60CC630E56C3E90@zch01exm26.fsl.freescale.net>
	<100CB1A1877FF245BDB7AF83A0E73FFE26BE4D@zch01exm28.fsl.freescale.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
In-Reply-To: <100CB1A1877FF245BDB7AF83A0E73FFE26BE4D@zch01exm28.fsl.freescale.net>
Cc: linuxppc-dev@ozlabs.org, lsorense@csclub.uwaterloo.ca, davem@davemloft.net,
	netdev@vger.kernel.org
Reply-To: avorontsov@ru.mvista.com
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
	<mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>

On Mon, Jan 11, 2010 at 11:47:37AM +0800, Wu Jiajun-B06378 wrote:
>  
> 'bd == ugeth->txBd[txQ]' has two possible statuses: 1)full queue.
> 2)empty queue.
> Removing 'netif_queue_stopped() == 0' will make transmitting stopping
> when the queue is full. 
> 
> I made a new patch for this oops.
[...]
> +		if ((bd == ugeth->txBd[txQ]) && (skb == NULL))
>  			break;

Hm. I wonder why do we need the 'bd == ugeth->txBd[txQ]' check
at all? The null skb will cause a kernel oops anyway.

I think the patch below should be sufficient for the fix.
Can you try it? Or if you tell me how to reproduce the issue
you observe, I can try it myself.

Thanks a lot!

diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
index 41ad2f3..a1a6d06 100644
--- a/drivers/net/ucc_geth.c
+++ b/drivers/net/ucc_geth.c
@@ -3279,13 +3279,12 @@ static int ucc_geth_tx(struct net_device *dev, u8 txQ)
 		/* Handle the transmitted buffer and release */
 		/* the BD to be used with the current frame  */
 
-		if (bd == ugeth->txBd[txQ]) /* queue empty? */
+		skb = ugeth->tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]];
+		if (!skb)
 			break;
 
 		dev->stats.tx_packets++;
 
-		skb = ugeth->tx_skbuff[txQ][ugeth->skb_dirtytx[txQ]];
-
 		if (skb_queue_len(&ugeth->rx_recycle) < RX_BD_RING_LEN &&
 			     skb_recycle_check(skb,
 				    ugeth->ug_info->uf_info.max_rx_buf_length +