netdev - Re: [PATCH v6 4/4] drivers: net: Add APM X-Gene SoC ethernet driver support.

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Date:	Tue, 17 Jun 2014 13:20:24 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	isubramanian@....com
Cc:	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, jcm@...hat.com,
	patches@....com, rapatel@....com, kchudgar@....com
Subject: Re: [PATCH v6 4/4] drivers: net: Add APM X-Gene SoC ethernet
 driver support.

From: Iyappan Subramanian <isubramanian@....com>
Date: Tue, 17 Jun 2014 12:21:08 -0700

> On Mon, Jun 16, 2014 at 9:42 PM, David Miller <davem@...emloft.net> wrote:
>> From: Iyappan Subramanian <isubramanian@....com>
>> Date: Mon, 16 Jun 2014 17:18:46 -0700
>>
>>> +static netdev_tx_t xgene_enet_start_xmit(struct sk_buff *skb,
>>> +                                      struct net_device *ndev)
>>> +{
>>> +     struct xgene_enet_pdata *pdata = netdev_priv(ndev);
>>> +     struct xgene_enet_desc_ring *tx_ring = pdata->tx_ring;
>>> +     struct xgene_enet_desc_ring *cp_ring = tx_ring->cp_ring;
>>> +     u32 tx_level, cq_level;
>>> +
>>> +     tx_level = xgene_enet_ring_len(tx_ring);
>>> +     cq_level = xgene_enet_ring_len(cp_ring);
>>> +     if (unlikely(tx_level > pdata->tx_qcnt_hi ||
>>> +                  cq_level > pdata->cp_qcnt_hi)) {
>>> +             netif_stop_queue(ndev);
>>> +             return NETDEV_TX_BUSY;
>>> +     }
>>> +
>>> +     if (xgene_enet_setup_tx_desc(tx_ring, skb))
>>> +             return NETDEV_TX_OK;
>>
>> If you return NETDEV_TX_OK, it is your responsibility to deal with the
>> SKB, because you own it.
>>
>> In particular, you have to free the packet.
> 
> skb freeing happens in xgene_enet_tx_completion().

You're not queueing up the packet when DMA mapping the packet fails,
which is the only condition that causes xgene_enet_setup_tx_desc() to
return an error, so xgene_enet_tx_completion() will not be called.

Can you really not see this?
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