[Bug,#14378] Problems with net/core/skbuff.c

Massimo Cetra a écrit :
> David Miller ha scritto:
>> From: "Rafael J. Wysocki" <rjw@sisk.pl>
>> Date: Mon, 12 Oct 2009 00:22:04 +0200 (CEST)
>>
>>  
>>> Bug-Entry    : http://bugzilla.kernel.org/show_bug.cgi?id=14378
>>> Subject        : Problems with net/core/skbuff.c
>>> Submitter    : Massimo Cetra <mcetra@navynet.it>
>>> Date        : 2009-10-08 14:51 (4 days old)
>>> References    : http://marc.info/?l=linux-kernel&m=125501488220358&w=4
>>>     
>>
>> I don't know what to do about this one.
>>
>> The user indicates that they have the vserver patches applied,
>> so maybe there is some interaction with that stuff.
>>   
> Actually i found another oops which is very similar to the previous one.
> Here, vserver is not involved, and the problem starts at drbd which
> lives in kernel space (the other oops started at ocfs2).
> 
> Both ocfs2 and drbd make heavy use of network I/O so i guess the problem
> is something in the network layer.
> 
> Anything i can do to help to debugging and solving this issue ?
> 
> Thanks
> Max
> 

Problem is kfree_skb() is called from irq context, wich is not allowed.

static void skb_release_head_state(struct sk_buff *skb)
{
...
if (skb->destructor) {
	WARN_ON(in_irq());
	skb->destructor();
}
...
}

virtio_net start_xmit() function calls free_old_xmit_skbs() and 
free_old_xmit_skbs() ultimately calls kfree_skb()

Quick fix would be to use dev_kfree_skb_any() instead,
because netpoll can definitly calls start_xmit()
with irq disabled.

Could you please following patch ?



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From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 13 Oct 2009 12:19:51 +0200

> Quick fix would be to use dev_kfree_skb_any() instead,
> because netpoll can definitly calls start_xmit()
> with irq disabled.

Indeed, because of netpoll(), that is something drivers
must be able to cope with.

> Could you please following patch ?

Indeed, let us know how Eric's patch works.

Thanks Eric!
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Eric Dumazet ha scritto:
> Could you please following patch ?
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 8d00976..54bf091 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -454,7 +454,7 @@ static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
>  		vi->dev->stats.tx_bytes += skb->len;
>  		vi->dev->stats.tx_packets++;
>  		tot_sgs += skb_vnet_hdr(skb)->num_sg;
> -		kfree_skb(skb);
> +		dev_kfree_skb_any(skb);
>  	}
>  	return tot_sgs;
>  }
>
>
>   
Thank you very much.

Compiling.
It' will be in production in a few minutes.
I'll let you know if the problem arises again.
give me a couple of days because this problem is randomly triggered.
Sometimes it happens multiple times a day, sometimes none.

Max


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Massimo Cetra ha scritto:
> Eric Dumazet ha scritto:
>> Could you please following patch ?
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 8d00976..54bf091 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -454,7 +454,7 @@ static unsigned int free_old_xmit_skbs(struct 
>> virtnet_info *vi)
>>          vi->dev->stats.tx_bytes += skb->len;
>>          vi->dev->stats.tx_packets++;
>>          tot_sgs += skb_vnet_hdr(skb)->num_sg;
>> -        kfree_skb(skb);
>> +        dev_kfree_skb_any(skb);
>>      }
>>      return tot_sgs;
>>  }
>>
>>
>>   
> Thank you very much.
>
> Compiling.
> It' will be in production in a few minutes.
> I'll let you know if the problem arises again.
> give me a couple of days because this problem is randomly triggered.
> Sometimes it happens multiple times a day, sometimes none.
>
Eric,
thanks for the patch.
The problem didn't arise again and i haven't seen any warning like that 
on both servers where that problem was happening more frequently.

I would say that it's fixed and if it's not, i'll let you know as soon 
as it happens again.

Thanks again,
Max



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