Re: [PATCH net v4] usbnet: fix EVENT_RX_PAUSED race in usbnet_skb_return()

[Jakub Kicinski]

On Tue, 20 Oct 2026 18:29:09 +0300 Ömer Mete Kaya wrote:
>  	struct sk_buff *skb;
>  	int num = 0;
> +	unsigned long flags;

reverse xmas tree ordering please

>  	local_bh_disable();
> +	spin_lock_irqsave(&dev->rxq_pause.lock, flags);
>  	clear_bit(EVENT_RX_PAUSED, &dev->flags);
> -
> -	while ((skb = skb_dequeue(&dev->rxq_pause)) != NULL) {
> +	while ((skb = __skb_dequeue(&dev->rxq_pause)) != NULL) {
> +		spin_unlock_irqrestore(&dev->rxq_pause.lock, flags);
>  		usbnet_skb_return(dev, skb);
> +		spin_lock_irqsave(&dev->rxq_pause.lock, flags);
>  		num++;
>  	}
> -
> +	spin_unlock_irqrestore(&dev->rxq_pause.lock, flags);

The retaking of the lock in the loop looks ugly / unnecessary to me

          struct sk_buff_head q;
          struct sk_buff *skb;
          unsigned long flags;
          int num = 0;

          __skb_queue_head_init(&q);

          local_bh_disable();
          spin_lock_irqsave(&dev->rxq_pause.lock, flags);
          clear_bit(EVENT_RX_PAUSED, &dev->flags);
          skb_queue_splice_init(&dev->rxq_pause, &q);
          spin_unlock_irqrestore(&dev->rxq_pause.lock, flags);

          while ((skb = __skb_dequeue(&q))) {
                  usbnet_skb_return(dev, skb);
                  num++;
          }
-- 
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