On Fri, 2015-07-24 at 20:38 +0300, Eugene Shatokhin wrote:
> 21.07.2015 15:04, Oliver Neukum пишет:
> > your analysis is correct and it looks like in addition to your proposed
> > fix locking needs to be simplified and a common lock to be taken.
> > Suggestions?
>
> Just an idea, I haven't tested it.
>
> How about moving the operations with dev->done under &list->lock in
> defer_bh, while keeping dev->done.lock too and changing
Why keep dev->done.lock?
Does it make sense at all?
> usbnet_terminate_urbs() as described below?
>
> Like this:
> @@ -428,12 +428,12 @@ static enum skb_state defer_bh(struct usbnet *dev,
> struct sk_buff *skb,
> old_state = entry->state;
> entry->state = state;
> __skb_unlink(skb, list);
> - spin_unlock(&list->lock);
> spin_lock(&dev->done.lock);
> __skb_queue_tail(&dev->done, skb);
> if (dev->done.qlen == 1)
> tasklet_schedule(&dev->bh);
> - spin_unlock_irqrestore(&dev->done.lock, flags);
> + spin_unlock(&dev->done.lock);
> + spin_unlock_irqrestore(&list->lock, flags);
> return old_state;
> }
> -------------------
>
> usbnet_terminate_urbs() can then be changed as follows:
>
> @@ -749,6 +749,20 @@ EXPORT_SYMBOL_GPL(usbnet_unlink_rx_urbs);
>
>
> /*-------------------------------------------------------------------------*/
>
> +static void wait_skb_queue_empty(struct sk_buff_head *q)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&q->lock, flags);
> + while (!skb_queue_empty(q)) {
> + spin_unlock_irqrestore(&q->lock, flags);
> + schedule_timeout(msecs_to_jiffies(UNLINK_TIMEOUT_MS));
> + set_current_state(TASK_UNINTERRUPTIBLE);
I suppose you want to invert those lines
> + spin_lock_irqsave(&q->lock, flags);
> + }
> + spin_unlock_irqrestore(&q->lock, flags);
> +}
> +
Your changes make sense, but it locks to me as if a lock would
become totally redundant.
Regards
Oliver
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