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 12:47:51 +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 06:31:00PM +0800, Yang Yingliang wrote:
> 
> On 2022/12/8 17:43, Leon Romanovsky wrote:
> > 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.
> While calling dev_kfree_skb(consume_skb), the SKB will not be marked as
> dropped,
> to keep the same meaning, so replace it with dev_consume_skb_irq()

This annotation code is relatively new (from 2013), while you are
changing code from pre-git era (<2005). 

Thanks

> 
> Thanks,
> Yang
> > 
> >    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
> > > 
> > .