Date:	Fri, 2 Mar 2012 09:34:42 -0500
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Christian Kujau <lists@...dbynature.de>
Cc:	netdev@...r.kernel.org, markus@...ppelsdorf.de,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: WARNING: at net/ipv4/tcp_input.c:3418

I just sent out to the netdev list a patch that might help:
 "[PATCH] tcp: fix tcp_retransmit_skb() to maintain MSS invariant"

There may be several corners of the code that have
MSS/pcount/sacked_out issues (and I am still looking around), but I
think this should fix one of them.

neal

On Thu, Mar 1, 2012 at 12:31 PM, Neal Cardwell <ncardwell@...gle.com> wrote:
> Thanks for the detailed reports.
>
> I am working on this, and have a theory and potential fix for a bug
> that relates to MSS changes and broken packet counts for SACKed skbs,
> which could conceivably lead to the warnings you're seeing. However,
> the bug that I am looking at is quite old. (Though it's possible it's
> being tickled more now, due to some interaction with recent changes.)
>
> To help provide more data, would you be able to run with 3.3.0-rc3 for
> a while (hopefully with roughly the same flavor of workload) and see
> if you run into the same problems?
>
> neal
>
> On Wed, Feb 29, 2012 at 12:41 PM, Christian Kujau <lists@...dbynature.de> wrote:
>> This is still happening with 3.3.0-rc5, .config & dmesg here:
>>
>>   http://nerdbynature.de/bits/3.3.0-rc4/ipv4/
>>
>> After the WARNING is printed often enough, the machine halts and has to be
>> powercycled. It appears that "lots of traffic" or "many connections" may
>> cause this, but unfortunately I haven't been able to reproduce this reliably.
>>
>> Any ideas on that one?
>>
>> Thanks,
>> Christian.
>>
>> On Sun, 26 Feb 2012 at 16:05, Christian Kujau wrote:
>>> Hi,
>>>
>>> I'm getting the same message here on PowerPC (32bit):
>>>
>>> ------------[ cut here ]------------
>>> WARNING: at /usr/local/src/linux-2.6-git/net/ipv4/tcp_input.c:3418
>>> Modules linked in: tun nfs ecryptfs netconsole therm_adt746x aes_generic
>>> arc4 b43 i2c_powermac sd_mod firewire_sbp2 mac80211 cfg80211 usb_storage
>>> scsi_mod
>>> NIP: c04720c4 LR: c04720b8 CTR: c049f2c8
>>> REGS: efff1c20 TRAP: 0700   Tainted: G        W     (3.3.0-rc4)
>>> MSR: 00029032 <EE,ME,IR,DR,RI>  CR: 42048448  XER: 20000000
>>> TASK = ee666780[1964] 'milkyway_0.50_p' THREAD: ee6c6000
>>> GPR00: ffffffff efff1cd0 ee666780 ee70c0a0 0000000b ffffffff c0426e70 00000000
>>> GPR08: 0000000b 00000001 00000000 00000009 42048448 1013488c 00000000 4f4a260f
>>> GPR16: 29c2cc42 00000502 00000000 000001cb 000001cb ee70c1b0 0000000b 00000000
>>> GPR24: 00000001 0000000c ffffffff ecef8580 0000000b 3c176da7 ee70c0a0 c0690000
>>> NIP [c04720c4] tcp_ack+0x720/0x10a0
>>> LR [c04720b8] tcp_ack+0x714/0x10a0
>>> Call Trace:
>>> [efff1cd0] [c04720b8] tcp_ack+0x714/0x10a0 (unreliable)
>>> [efff1d60] [c04756f0] tcp_rcv_established+0x214/0x6c4
>>> [efff1d90] [c047d1dc] tcp_v4_do_rcv+0xd8/0x2a4
>>> [efff1dd0] [c047db0c] tcp_v4_rcv+0x764/0x8e4
>>> [efff1e10] [c045ac6c] ip_local_deliver+0xe0/0x1dc
>>> [efff1e30] [c045a870] ip_rcv+0x378/0x694
>>> [efff1e50] [c04302c8] __netif_receive_skb+0x320/0x52c
>>> [efff1eb0] [c0430790] napi_skb_finish+0x6c/0x90
>>> [efff1ec0] [c03b2e20] gem_poll+0x694/0x1274
>>> [efff1f50] [c0430ccc] net_rx_action+0x1d4/0x278
>>> [efff1fa0] [c003bac0] __do_softirq+0xf4/0x1bc
>>> [efff1ff0] [c00103b0] call_do_softirq+0x14/0x24
>>> [ee6c7ee0] [c00070ac] do_softirq+0xfc/0x128
>>> [ee6c7f00] [c003b73c] irq_exit+0xac/0xcc
>>> [ee6c7f10] [c00071d8] do_IRQ+0x8c/0x1b0
>>> [ee6c7f40] [c0012e60] ret_from_except+0x0/0x14
>>> Instruction dump:
>>> 2f800000 419e0020 73250008 4182046c 38a0ffff 7ec4b378 7fc3f378 7c0903a6
>>> 4e800421 801e04e8 7c1a0378 54090ffe <0f090000> 809e04e4 54890ffe 0f090000
>>> ---[ end trace de136ca1488e7a83 ]---
>>> Leak s=4294967295 1
>>>
>>>
>>> Yesterday the machine panick'ed and shutdown shortly after the message
>>> appeared. From today's logs I can see the message appeared some 10 hours
>>> ago but the machine is still up & running. I've been running 3.3.0-rc4 for
>>> some time now, but network activity went up a few days ago, so that
>>> might've triggered it.
>>>
>>> Ful dmesg & .config: http://nerdbynature.de/bits/3.3.0-rc4/ipv4/
>>>
>>> Note: the machine's internal battery seems to be bad, that's why the
>>> timestamps during bootup are b0rked in those logfiles.
>>>
>>> Please Cc me on replies as I'm not subscribed to netdev.
>>>
>>> Thanks,
>>> Christian.
>>> --
>>> BOFH excuse #444:
>>>
>>> overflow error in /dev/null
>>>
>>
>> --
>> BOFH excuse #38:
>>
>> secretary plugged hairdryer into UPS
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