linux-kernel - Re: [PATCH 2/2] can: bcm: check the result of can_send() in bcm_can

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Message-ID: <88a5cdf5-d8e3-3822-7864-80aecf3c4ac3@huawei.com>
Date:   Thu, 8 Sep 2022 20:09:06 +0800
From:   "Ziyang Xuan (William)" <william.xuanziyang@...wei.com>
To:     Oliver Hartkopp <socketcan@...tkopp.net>, <mkl@...gutronix.de>,
        <edumazet@...gle.com>, <kuba@...nel.org>,
        <linux-can@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] can: bcm: check the result of can_send() in
 bcm_can_tx()

> Sorry, but NACK.
> 
> The curr_frame counter handles the sequence counter of multiplex messages.
> 
> Even when this single send attempt failed the curr_frame counter has to continue.
> 
> For that reason the comment about statistics *before* the curr_frame++ might be misleading.
> 
> A potential improvement could be:
> 
>     if (!(can_send(skb, 1)))
>         op->frames_abs++;
> 
>     op->currframe++;
> 
> But as op->frames_abs is a functional unused(!) value for tx ops and only displayed via procfs I would NOT tag such improvement as a 'fix' which might then be queued up for stable.
> 
I will modify and remove 'Fixes' tag in v2.

Thank you for your review.

> This could be something for the can-next tree ...
> 
> Best regards,
> Oliver
> 
> 
> On 08.09.22 05:04, Ziyang Xuan wrote:
>> If can_send() fail, it should not update statistics in bcm_can_tx().
>> Add the result check for can_send() in bcm_can_tx().
>>
>> Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
>> Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>
>> ---
>>   net/can/bcm.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/can/bcm.c b/net/can/bcm.c
>> index e2783156bfd1..8f5d704a409f 100644
>> --- a/net/can/bcm.c
>> +++ b/net/can/bcm.c
>> @@ -298,7 +298,8 @@ static void bcm_can_tx(struct bcm_op *op)
>>       /* send with loopback */
>>       skb->dev = dev;
>>       can_skb_set_owner(skb, op->sk);
>> -    can_send(skb, 1);
>> +    if (can_send(skb, 1))
>> +        goto out;
>>         /* update statistics */
>>       op->currframe++;
> .