netdev - Re: [PATCH 3/3] net: lantiq: Use napi_complete

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Date:   Mon, 17 Aug 2020 17:48:52 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Hauke Mehrtens <hauke@...ke-m.de>, davem@...emloft.net
Cc:     kuba@...nel.org, netdev@...r.kernel.org,
        martin.blumenstingl@...glemail.com
Subject: Re: [PATCH 3/3] net: lantiq: Use napi_complete_done()



On 8/17/20 5:33 PM, Eric Dumazet wrote:
> 
> 
> On 8/17/20 2:17 PM, Hauke Mehrtens wrote:
>> On 8/16/20 8:07 PM, Eric Dumazet wrote:
>>>
>>>
>>> On 8/15/20 11:33 AM, Hauke Mehrtens wrote:
>>>> Use napi_complete_done() and activate the interrupts when this function
>>>> returns true. This way the generic NAPI code can take care of activating
>>>> the interrupts.
>>>>
>>>> Signed-off-by: Hauke Mehrtens <hauke@...ke-m.de>
>>>> ---
>>>>  drivers/net/ethernet/lantiq_xrx200.c | 8 ++------
>>>>  1 file changed, 2 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
>>>> index f34e4dc8c661..674ffb2ecd9a 100644
>>>> --- a/drivers/net/ethernet/lantiq_xrx200.c
>>>> +++ b/drivers/net/ethernet/lantiq_xrx200.c
>>>> @@ -229,10 +229,8 @@ static int xrx200_poll_rx(struct napi_struct *napi, int budget)
>>>>  		}
>>>>  	}
>>>>  
>>>> -	if (rx < budget) {
>>>> -		napi_complete(&ch->napi);
>>>> +	if (napi_complete_done(&ch->napi, rx))
>>>>  		ltq_dma_enable_irq(&ch->dma);
>>>> -	}
>>>>  
>>>>  	return rx;
>>>>  }
>>>> @@ -271,10 +269,8 @@ static int xrx200_tx_housekeeping(struct napi_struct *napi, int budget)
>>>>  	if (netif_queue_stopped(net_dev))
>>>>  		netif_wake_queue(net_dev);
>>>>  
>>>> -	if (pkts < budget) {
>>>> -		napi_complete(&ch->napi);
>>>> +	if (napi_complete_done(&ch->napi, pkts))
>>>>  		ltq_dma_enable_irq(&ch->dma);
>>>> -	}
>>>>  
>>>>  	return pkts;
>>>>  }
>>>>
>>>
>>>
>>> This looks buggy to me.
>>
>> Hi Eric,
>>
>> Thanks for looking at the patch.
>>
>> What exactly looks buggy to you?
> 
> You removed the " if (rx < budget) "
> 
> But you must not.
> 
> Drivers have to keep the test.
> 
> Something like that seems more correct :
> 
> diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
> index 1645e4e7ebdbb3c7abff8fe4207273df20f123d4..e3d617d387ed0f5593c3ba81d1d531d463bb5a6e 100644
> --- a/drivers/net/ethernet/lantiq_xrx200.c
> +++ b/drivers/net/ethernet/lantiq_xrx200.c
> @@ -230,8 +230,8 @@ static int xrx200_poll_rx(struct napi_struct *napi, int budget)
>         }
>  
>         if (rx < budget) {
> -               napi_complete(&ch->napi);
> -               ltq_dma_enable_irq(&ch->dma);
> +               if (napi_complete(&ch->napi, rx))

Obviously : s/napi_complete/napi_complete_done/

> +                       ltq_dma_enable_irq(&ch->dma);
>         }
>  
>         return rx;
> @@ -269,8 +269,8 @@ static int xrx200_tx_housekeeping(struct napi_struct *napi, int budget)
>         netdev_completed_queue(ch->priv->net_dev, pkts, bytes);
>  
>         if (pkts < budget) {
> -               napi_complete(&ch->napi);
> -               ltq_dma_enable_irq(&ch->dma);
> +               if (napi_complete(&ch->napi, pkts))

Same : s/napi_complete/napi_complete_done/


> +                       ltq_dma_enable_irq(&ch->dma);
>         }
>  
>         return pkts;
>