Subject: Re: [PATCH] af_packet: Don't use skb after dev_queue_xmit()

From: Michael Breuer <[email-masked]>
Date: Tue, 19 Jan 2010 20:01:10 -0500

On 1/19/2010 5:45 PM, Jarek Poplawski wrote:
> On Tue, Jan 19, 2010 at 03:06:01PM -0500, Michael Breuer wrote:
>    
>> On 1/19/2010 2:59 PM, Jarek Poplawski wrote:
>>      
>>> On Tue, Jan 19, 2010 at 10:47:27AM -0500, Michael Breuer wrote:
>>> ...
>>>        
>>>> Still get the warning... but now 60 bytes.
>>>> Jan 19 10:43:50 mail kernel: ------------[ cut here ]------------
>>>> Jan 19 10:43:50 mail kernel: WARNING: at lib/dma-debug.c:902
>>>>          
>>> Thanks for trying this.
>>> Jarek P.
>>>        
>> NP. Let me know what else I can do to help with this one. Note that
>> it seems innocuous. I'll continue with the older set and no dmar for
>> now and see if I get another crash.
>>      
> Maybe one more idea to try (not compiled).
>
> Jarek P.
> ---
>
>   drivers/net/sky2.c |    6 ++++--
>   1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/sky2.c b/drivers/net/sky2.c
> index 7650f73..cdebdd3 100644
> --- a/drivers/net/sky2.c
> +++ b/drivers/net/sky2.c
> @@ -2252,12 +2252,14 @@ static struct sk_buff *receive_copy(struct sky2_port *sky2,
>   	skb = netdev_alloc_skb_ip_align(sky2->netdev, length);
>   	if (likely(skb)) {
>   		pci_dma_sync_single_for_cpu(sky2->hw->pdev, re->data_addr,
> -					    length, PCI_DMA_FROMDEVICE);
> +					    pci_unmap_len(re, data_size),
> +					    PCI_DMA_FROMDEVICE);
>   		skb_copy_from_linear_data(re->skb, skb->data, length);
>   		skb->ip_summed = re->skb->ip_summed;
>   		skb->csum = re->skb->csum;
>   		pci_dma_sync_single_for_device(sky2->hw->pdev, re->data_addr,
> -					       length, PCI_DMA_FROMDEVICE);
> +					       pci_unmap_len(re, data_size),
> +					       PCI_DMA_FROMDEVICE);
>   		re->skb->ip_summed = CHECKSUM_NONE;
>   		skb_put(skb, length);
>   	}
>    
That not only compiled, but it cleared the error as well. Additionally, 
I used to see a bit of a delay receiving the login prompt when first 
connecting to the box by ssh. That delay is gone with this patch. I'd 
guess that the warning wasn't quite as innocuous as I thought.
Note: tested on 2.6.32.4.  I'll leave this up for a bit before 
attempting to move back to head.