netdev - Re: [PATCH] tg3: fix tigon3_dma_hwbug

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Date:	Sat, 22 Oct 2011 10:54:33 +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 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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