Messages in this thread | | | Subject | Re: Several races in "usbnet" module (kernel 4.1.x) | From | Eugene Shatokhin <> | Date | Mon, 27 Jul 2015 16:53:49 +0300 |
| |
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
| |