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

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Message-ID: <840947dc-8560-ca51-f4d6-0e2628c181b1@huawei.com>
Date:   Thu, 8 Dec 2022 18:31:00 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Leon Romanovsky <leon@...nel.org>
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 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()

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
>>
> .