Date:	Tue, 12 May 2009 15:48:44 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michael Guntsche <mike@...loops.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Andy Fleming <afleming@...escale.com>
Subject: Re: [BUG] 2.6.30-rc4: Kernel BUG under network load with gianfar

On Wed, 13 May 2009 00:34:52 +0200
Michael Guntsche <mike@...loops.com> wrote:

> 
> On May 5, 2009, at 10:29 PM, Michael Guntsche wrote:
> >
> > Here is a full dump from the console again including the line  
> > before the "cut here" text.
> > Wan is the device going to the ADSL-modem.
> >
> > [  172.251007] skb_over_panic: text:c0187650 len:1514 put:1514  
> > head:c79a8800 data:c79a8880 tail:0xc79a8e6a end:0xc79a8e60 dev:wan
> >
> >
> 
> since I still had the panics with rc5 I went ahead and started  
> looking for the commit that caused the problem. After some testing  
> (actually a lot of compile cycles) I found out that commit
> 
> 0fd56bb5be6455d0d42241e65aed057244665e5e gianfar: Add support for skb  
> recycling
> 
> was the culprit.

Thanks.  Let's CC andy.

> The commits before it work and starting with this  
> one the skb_over_pancis start to occur.
> 
> This is as far as I can debug it though. Maybe someone more  
> knowledgeable about this stuff could take a look at it or tell me how  
> I can figure out what's happening exactly.
> 
> For testing purposes I reverted this commit from the current master  
> and it has been running the last hour without any problems. Before  
> that the panic would occur almost immediately after a download was  
> started.
> 
> 
> Once again part of the panic which is more or less the same everytime...
> 
> [  113.218513] skb_over_panic: text:c015a74c len:1514 put:1514  
> head:c7a07800 data:c7a07880 tail:0xc7a07e6a end:0xc7a07e60 dev:wan
> [  113.230039] ------------[ cut here ]------------
> [  113.234669] kernel BUG at net/core/skbuff.c:124!
> [  113.239302] Oops: Exception in kernel mode, sig: 5 [#1]
> [  113.244539] MikroTik RouterBOARD 600 series
> [  113.248729] Modules linked in:
> [  113.251797] NIP: c01a2ad0 LR: c01a2ad0 CTR: c014e37c
> [  113.256776] REGS: c0367cb0 TRAP: 0700   Not tainted  (2.6.29-rc3)
> [  113.262883] MSR: 00029032 <EE,ME,CE,IR,DR>  CR: 24002024  XER:  
> 20000000
> [  113.269562] TASK = c0344588[0] 'swapper' THREAD: c0366000
> [  113.274799] GPR00: c01a2ad0 c0367d60 c0344588 00000085 00002625  
> ffffffff c014b948 00002625
> [  113.283223] GPR08: 00000030 c0370000 00002625 c03723a8 84002082  
> 1001b1cc 007d66c0 00000008
> [  113.291647] GPR16: c02e70bc c02e70e8 c78423d8 c0345678 00000040  
> c0366000 c7971800 00000000
> [  113.300071] GPR24: 00000001 00000000 c78eb300 c7971ff0 c7842000  
> 000005ea c795c3c0 c7a07880
> [  113.308689] NIP [c01a2ad0] skb_over_panic+0x48/0x5c
> [  113.313582] LR [c01a2ad0] skb_over_panic+0x48/0x5c
> [  113.318382] Call Trace:
> [  113.320838] [c0367d60] [c01a2ad0] skb_over_panic+0x48/0x5c  
> (unreliable)
> [  113.327485] [c0367d70] [c01a42cc] skb_put+0x5c/0x60
> [  113.332390] [c0367d80] [c015a74c] gfar_clean_rx_ring+0x20c/0x438
> [  113.338422] [c0367dd0] [c015c160] gfar_poll+0x288/0x370
> [  113.343672] [c0367e30] [c01af538] net_rx_action+0x94/0x188
> [  113.349191] [c0367e60] [c002d0f0] __do_softirq+0x84/0x124
> [  113.354621] [c0367e90] [c00063f8] do_softirq+0x58/0x5c
> [  113.359781] [c0367ea0] [c002cf6c] irq_exit+0x94/0x98
> [  113.364768] [c0367eb0] [c000649c] do_IRQ+0xa0/0xc4
> [  113.369582] [c0367ed0] [c0014220] ret_from_except+0x0/0x14
> [  113.375101] --- Exception: 501 at cpu_idle+0xa0/0xec
> [  113.375109]     LR = cpu_idle+0xa0/0xec
> [  113.383923] [c0367f90] [c0009164] cpu_idle+0x50/0xec (unreliable)
> [  113.390054] [c0367fb0] [c027c8bc] __got2_end+0x58/0x68
> [  113.395225] [c0367fc0] [c03167e4] start_kernel+0x220/0x2a0
> [  113.400731] [c0367ff0] [00003438] 0x3438
> 

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