From: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>
To: Oliver Neukum <oneukum@suse.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-usb@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: Several races in "usbnet" module (kernel 4.1.x)
Date: Mon, 27 Jul 2015 16:53:49 +0300 [thread overview]
Message-ID: <55B637ED.2080905@rosalab.ru> (raw)
In-Reply-To: <1438000168.32457.18.camel@suse.com>
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
next prev parent reply other threads:[~2015-07-27 13:53 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-20 18:13 Several races in "usbnet" module (kernel 4.1.x) Eugene Shatokhin
2015-07-21 12:04 ` Oliver Neukum
2015-07-24 17:38 ` Eugene Shatokhin
2015-07-27 12:29 ` Oliver Neukum
2015-07-27 13:53 ` Eugene Shatokhin [this message]
2015-07-21 13:07 ` Oliver Neukum
2015-07-21 14:22 ` Oliver Neukum
2015-07-22 18:33 ` Eugene Shatokhin
2015-07-23 9:15 ` Oliver Neukum
2015-07-24 14:41 ` Eugene Shatokhin
2015-07-27 10:00 ` Oliver Neukum
2015-07-27 14:23 ` Eugene Shatokhin
2015-08-14 16:55 ` Eugene Shatokhin
2015-08-14 16:58 ` [PATCH] usbnet: Fix two races between usbnet_stop() and the BH Eugene Shatokhin
2015-08-19 1:54 ` David Miller
2015-08-19 7:57 ` Eugene Shatokhin
2015-08-19 10:54 ` Bjørn Mork
2015-08-19 11:59 ` Eugene Shatokhin
2015-08-19 12:31 ` Bjørn Mork
2015-08-24 12:20 ` Eugene Shatokhin
2015-08-24 13:29 ` Bjørn Mork
2015-08-24 17:00 ` Eugene Shatokhin
2015-08-25 12:31 ` Oliver Neukum
2015-08-24 17:43 ` David Miller
2015-08-24 18:06 ` Alan Stern
2015-08-24 18:21 ` Alan Stern
2015-08-25 12:36 ` Oliver Neukum
2015-08-24 18:35 ` David Miller
2015-08-24 18:12 ` Eugene Shatokhin
2015-07-23 9:43 ` Several races in "usbnet" module (kernel 4.1.x) Oliver Neukum
2015-07-23 11:39 ` Eugene Shatokhin
2015-08-24 20:13 ` [PATCH 0/2] usbnet: Fix 2 problems in usbnet_stop() Eugene Shatokhin
2015-08-24 20:13 ` [PATCH 1/2] usbnet: Get EVENT_NO_RUNTIME_PM bit before it is cleared Eugene Shatokhin
2015-08-25 13:01 ` Oliver Neukum
2015-08-25 14:16 ` Bjørn Mork
2015-08-25 14:22 ` Oliver Neukum
2015-08-26 2:44 ` David Miller
2015-08-24 20:13 ` [PATCH 2/2] usbnet: Fix a race between usbnet_stop() and the BH Eugene Shatokhin
2015-08-24 21:01 ` Bjørn Mork
2015-08-28 8:09 ` Eugene Shatokhin
2015-08-28 8:55 ` Bjørn Mork
2015-08-28 10:42 ` Eugene Shatokhin
2015-08-31 7:32 ` Bjørn Mork
2015-08-31 8:50 ` Eugene Shatokhin
2015-09-01 7:58 ` Oliver Neukum
2015-09-01 13:54 ` Eugene Shatokhin
2015-09-01 14:05 ` [PATCH] " Eugene Shatokhin
2015-09-08 7:24 ` Eugene Shatokhin
2015-09-08 7:37 ` Bjørn Mork
2015-09-08 7:48 ` Oliver Neukum
2015-09-08 20:18 ` David Miller
2015-09-01 7:57 ` [PATCH 2/2] " Oliver Neukum
2015-08-26 2:45 ` David Miller
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