netdev - Re: [PATCH net v3] ethernet: s2io: don't call dev_kfree_skb() under spin_lock

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Date:   Thu, 8 Dec 2022 11:43:32 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Yang Yingliang <yangyingliang@...wei.com>
Cc:     netdev@...r.kernel.org, jdmason@...zu.us, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net v3] ethernet: s2io: don't call dev_kfree_skb() under
 spin_lock_irqsave()

On Thu, Dec 08, 2022 at 05:24:11PM +0800, Yang Yingliang wrote:
> The dev_kfree_skb() is defined as consume_skb(), and it is not allowed
> to call consume_skb() from hardware interrupt context or with interrupts
> being disabled. So replace dev_kfree_skb() with dev_consume_skb_irq()
> under spin_lock_irqsave().

While dev_kfree_skb and consume_skb are the same, the dev_kfree_skb_irq
and dev_consume_skb_irq are not. You can't blindly replace
dev_kfree_skb with dev_consume_skb_irq. You should check every place, analyze
and document why specific option was chosen.

  3791 static inline void dev_kfree_skb_irq(struct sk_buff *skb)
  3792 {
  3793         __dev_kfree_skb_irq(skb, SKB_REASON_DROPPED);
  3794 }
  3795
  3796 static inline void dev_consume_skb_irq(struct sk_buff *skb)
  3797 {
  3798         __dev_kfree_skb_irq(skb, SKB_REASON_CONSUMED);
  3799 }

Thanks


> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> ---
> v2 -> v3:
>   Update commit message.
> 
> v1 -> v2:
>   Add fix tag.
> ---
>  drivers/net/ethernet/neterion/s2io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/neterion/s2io.c b/drivers/net/ethernet/neterion/s2io.c
> index 1d3c4474b7cb..a83d61d45936 100644
> --- a/drivers/net/ethernet/neterion/s2io.c
> +++ b/drivers/net/ethernet/neterion/s2io.c
> @@ -2386,7 +2386,7 @@ static void free_tx_buffers(struct s2io_nic *nic)
>  			skb = s2io_txdl_getskb(&mac_control->fifos[i], txdp, j);
>  			if (skb) {
>  				swstats->mem_freed += skb->truesize;
> -				dev_kfree_skb(skb);
> +				dev_consume_skb_irq(skb);
>  				cnt++;
>  			}
>  		}
> -- 
> 2.25.1
>