netdev - Re: [PATCH] tg3: fix tigon3_dma_hwbug

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Date:	Sat, 22 Oct 2011 16:30:47 +0300
From:	Ari Savolainen <ari.m.savolainen@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	RongQing Li <roy.qing.li@...il.com>,
	David Miller <davem@...emloft.net>, richardcochran@...il.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tg3: fix tigon3_dma_hwbug_workaround()

I tested the patch. It works. The panics are gone.

Thanks,
Ari

2011/10/22 Ari Savolainen <ari.m.savolainen@...il.com>:
> I tried a similar patch earlier and got another panic with that. I was
> quite tired at that time and may have made a mistake. I'll test Eric's
> patch either later today or tomorrow.
>
> Ari
>
> 2011/10/22 Eric Dumazet <eric.dumazet@...il.com>:
>> Ari got kernel panics using tg3 NIC, and bisected to 2669069aacc9 "tg3:
>> enable transmit time stamping."
>>
>> This is because tigon3_dma_hwbug_workaround() might alloc a new skb and
>> free the original. We panic when skb_tx_timestamp() is called on freed
>> skb.
>>
>> Reported-by: Ari Savolainen <ari.m.savolainen@...il.com>
>> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
>> ---
>>  drivers/net/tg3.c |    8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
>> index 4a1374d..6149dc5 100644
>> --- a/drivers/net/tg3.c
>> +++ b/drivers/net/tg3.c
>> @@ -6029,12 +6029,12 @@ static void tg3_tx_skb_unmap(struct tg3_napi *tnapi, u32 entry, int last)
>>
>>  /* Workaround 4GB and 40-bit hardware DMA bugs. */
>>  static int tigon3_dma_hwbug_workaround(struct tg3_napi *tnapi,
>> -                                      struct sk_buff *skb,
>> +                                      struct sk_buff **pskb,
>>                                       u32 *entry, u32 *budget,
>>                                       u32 base_flags, u32 mss, u32 vlan)
>>  {
>>        struct tg3 *tp = tnapi->tp;
>> -       struct sk_buff *new_skb;
>> +       struct sk_buff *new_skb, *skb = *pskb;
>>        dma_addr_t new_addr = 0;
>>        int ret = 0;
>>
>> @@ -6076,7 +6076,7 @@ static int tigon3_dma_hwbug_workaround(struct tg3_napi *tnapi,
>>        }
>>
>>        dev_kfree_skb(skb);
>> -
>> +       *pskb = new_skb;
>>        return ret;
>>  }
>>
>> @@ -6305,7 +6305,7 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
>>                 */
>>                entry = tnapi->tx_prod;
>>                budget = tg3_tx_avail(tnapi);
>> -               if (tigon3_dma_hwbug_workaround(tnapi, skb, &entry, &budget,
>> +               if (tigon3_dma_hwbug_workaround(tnapi, &skb, &entry, &budget,
>>                                                base_flags, mss, vlan))
>>                        goto out_unlock;
>>        }
>>
>>
>>
>
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