27.07.2015 15:29, Oliver Neukum пишет:
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?
I think it does.
Both skb_queue_tail(&dev->done, skb) called from rx_process() and
skb_dequeue (&dev->done) called from usbnet_bh() take dev->done.lock
internally. So, to synchronize accesses to dev->done, one needs that
lock in defer_bh() too.
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
Do you mean
+set_current_state(TASK_UNINTERRUPTIBLE);
+schedule_timeout(msecs_to_jiffies(UNLINK_TIMEOUT_MS));
?
+ 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,
Eugene
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