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

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Message-ID: <1caf3e52-c862-e702-c833-153f130b790a@hartkopp.net>
Date:   Thu, 8 Sep 2022 08:47:57 +0200
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Ziyang Xuan <william.xuanziyang@...wei.com>, 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.

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++;