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From:   xu <xu.xin.sc@gmail.com>
To:     edumazet@google.com
Cc:     davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        yang.yang29@zte.com.cn
Subject: [PATCH] net: add net device refcount tracker to pneigh_queue
Date:   Sat,  5 Aug 2023 06:46:06 +0000
Message-Id: <20230805064606.237648-1-xu.xin16@zte.com.cn>
In-Reply-To: <CANn89iK61nt5o7KBZyjqVP6Q1EREvzg-x_bos8hSGSmwfwZRBw@mail.gmail.com>
References: <CANn89iK61nt5o7KBZyjqVP6Q1EREvzg-x_bos8hSGSmwfwZRBw@mail.gmail.com>
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>> Add a static net device refcount tracker to neighbour.c to track
>> dev's refcnt when pneigh enqueuing and dequeuing.
>>
>> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
>> Reviewed-by: Yang Yang <yang.yang.29@zte.com.cn>
>> Cc: Kuang Mingfu <kuang.mingfu@zte.com.cn>
>> ---
>
>
>Can you explain how this patch was tested ?
>
>Thanks.

Sorry, I misunderstand the usage of netdev_hold and its netdevice_tracker.

I thought this tracker was simple enough, so I just added an additional netdev_hold
in the same postion and test if there is a warning "unregister_netdevice: waiting for ...".

But as you said, we need a separate netdevice_tracker per netdev_hold(), and specially `per dev`?

Actually, I'm still a little confused.

For example, here, can I move this netdevice_tracker into struct sk_buff ?

>diff --git a/net/core/neighbour.c b/net/core/neighbour.c
>index ddd0f32de20e..56e87130fa95 100644
>--- a/net/core/neighbour.c
>+++ b/net/core/neighbour.c
>@@ -61,6 +61,7 @@ static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
> static const struct seq_operations neigh_stat_seq_ops;
> #endif
>
>+static netdevice_tracker pneigh_queue_dev_tracker;
> /*
>    Neighbour hash table buckets are protected with rwlock tbl->lock.
>
>@@ -364,7 +365,7 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net,
> 	spin_unlock_irqrestore(&list->lock, flags);
>
> 	while ((skb = __skb_dequeue(&tmp))) {
>-		dev_put(skb->dev);
>+		netdev_put(skb->dev, &pneigh_queue_dev_tracker);
> 		kfree_skb(skb);
> 	}
> }
>@@ -1633,7 +1634,7 @@ static void neigh_proxy_process(struct timer_list *t)
> 				kfree_skb(skb);
> 			}
>
>-			dev_put(dev);
>+			netdev_put(skb->dev, &pneigh_queue_dev_tracker);
> 		} else if (!sched_next || tdif < sched_next)
> 			sched_next = tdif;
> 	}
>@@ -1673,7 +1674,7 @@ void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,
> 			sched_next = tbl->proxy_timer.expires;
> 	}
> 	skb_dst_drop(skb);
>-	dev_hold(skb->dev);
>+	netdev_hold(skb->dev, &pneigh_queue_dev_tracker, GFP_KERNEL);
> 	__skb_queue_tail(&tbl->proxy_queue, skb);
> 	p->qlen++;
> 	mod_timer(&tbl->proxy_timer, sched_next);