netdev - Re: [PATCH net 1/8] amt: use workqueue for gateway side message handling

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Message-ID: <20220713205509.2a79563a@kernel.org>
Date:   Wed, 13 Jul 2022 20:55:09 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net 1/8] amt: use workqueue for gateway side message
 handling

On Tue, 12 Jul 2022 10:57:07 +0000 Taehee Yoo wrote:
> @@ -2392,12 +2429,14 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
>  	skb->pkt_type = PACKET_MULTICAST;
>  	skb->ip_summed = CHECKSUM_NONE;
>  	len = skb->len;
> +	rcu_read_lock_bh();
>  	if (__netif_rx(skb) == NET_RX_SUCCESS) {
>  		amt_update_gw_status(amt, AMT_STATUS_RECEIVED_QUERY, true);
>  		dev_sw_netstats_rx_add(amt->dev, len);
>  	} else {
>  		amt->dev->stats.rx_dropped++;
>  	}
> +	rcu_read_unlock_bh();
>  
>  	return false;
>  }

The RCU lock addition looks potentially unrelated?

> @@ -2892,10 +3007,21 @@ static int amt_dev_stop(struct net_device *dev)
>  	struct amt_dev *amt = netdev_priv(dev);
>  	struct amt_tunnel_list *tunnel, *tmp;
>  	struct socket *sock;
> +	struct sk_buff *skb;
> +	int i;
>  
>  	cancel_delayed_work_sync(&amt->req_wq);
>  	cancel_delayed_work_sync(&amt->discovery_wq);
>  	cancel_delayed_work_sync(&amt->secret_wq);
> +	cancel_work_sync(&amt->event_wq);

Are you sure the work will not get scheduled again?
What has stopped packet Rx at this point?

> +	for (i = 0; i < AMT_MAX_EVENTS; i++) {
> +		skb = amt->events[i].skb;
> +		if (skb)
> +			kfree_skb(skb);
> +		amt->events[i].event = AMT_EVENT_NONE;
> +		amt->events[i].skb = NULL;
> +	}
> 
>  	/* shutdown */
>  	sock = rtnl_dereference(amt->sock);
> @@ -3051,6 +3177,8 @@ static int amt_newlink(struct net *net, struct net_device *dev,
>  		amt->max_tunnels = AMT_MAX_TUNNELS;
>  
>  	spin_lock_init(&amt->lock);
> +	amt->event_idx = 0;
> +	amt->nr_events = 0;

no need to init member of netdev_priv() to 0, it's zalloc'ed

>  	amt->max_groups = AMT_MAX_GROUP;
>  	amt->max_sources = AMT_MAX_SOURCE;
>  	amt->hash_buckets = AMT_HSIZE;