netdev - Re: [PATCH net-next v3 1/4] net: microchip: vcap: Add vcap_get

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Date:   Tue, 06 Dec 2022 13:31:53 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        Steen.Hegelund@...rochip.com, lars.povlsen@...rochip.com,
        daniel.machon@...rochip.com, richardcochran@...il.com,
        UNGLinuxDriver@...rochip.com, olteanv@...il.com
Subject: Re: [PATCH net-next v3 1/4] net: microchip: vcap: Add vcap_get_rule

Hello,

On Sat, 2022-12-03 at 11:43 +0100, Horatiu Vultur wrote:
> @@ -632,32 +264,22 @@ static int vcap_show_admin(struct vcap_control *vctrl,
>  			   struct vcap_admin *admin,
>  			   struct vcap_output_print *out)
>  {
> -	struct vcap_rule_internal *elem, *ri;
> +	struct vcap_rule_internal *elem;
> +	struct vcap_rule *vrule;
>  	int ret = 0;
>  
>  	vcap_show_admin_info(vctrl, admin, out);
> -	mutex_lock(&admin->lock);
>  	list_for_each_entry(elem, &admin->rules, list) {

Not strictly related to this patch, as the patter is AFAICS already
there in other places, but I'd like to understand the admin->rules
locking schema.

It looks like addition/removal are protected by admin->lock, but
traversal is usually lockless, which in turn looks buggy ?!?

Note: as this patch does not introduce the mentioned behavior, I'm not
going to block the series for the above.

Thanks,

Paolo
> -		ri = vcap_dup_rule(elem);
> -		if (IS_ERR(ri)) {
> -			ret = PTR_ERR(ri);
> -			goto err_unlock;
> +		vrule = vcap_get_rule(vctrl, elem->data.id);
> +		if (IS_ERR_OR_NULL(vrule)) {
> +			ret = PTR_ERR(vrule);
> +			break;
>  		}
> -		/* Read data from VCAP */
> -		ret = vcap_read_rule(ri);
> -		if (ret)
> -			goto err_free_rule;
> +
>  		out->prf(out->dst, "\n");
> -		vcap_show_admin_rule(vctrl, admin, out, ri);
> -		vcap_free_rule((struct vcap_rule *)ri);
> +		vcap_show_admin_rule(vctrl, admin, out, to_intrule(vrule));
> +		vcap_free_rule(vrule);
>  	}
> -	mutex_unlock(&admin->lock);
> -	return 0;
> -
> -err_free_rule:
> -	vcap_free_rule((struct vcap_rule *)ri);
> -err_unlock:
> -	mutex_unlock(&admin->lock);
>  	return ret;
>  }