Date:	Wed, 30 Dec 2009 16:21:35 -0500
From:	Michael Breuer <mbreuer@...jas.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Berck E. Nash" <flyboy@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: audit.c skb - tty race condition - was sky2 panic in 2.6.32.1
 under load (new oops)

On 12/30/2009 4:15 PM, Michael Breuer wrote:
> On 12/30/2009 3:44 PM, Michael Breuer wrote:
>> A couple more observations:
>>
>> 1) enabling auditd for runlevel 3 mitigates the issue
>> 2) starting a remote x session (XDMCP) while under load and while 
>> auditd is already running also triggers the sky2 interrupt status 
>> messages - so maybe not tty1 - but some sort of X & auditd 
>> interaction. Even in this case, the frequency of the error messages 
>> is much less than when auditd is started in runlevel 5 for the first 
>> time.
> And just for some certainty - running with audit=0, the errors do not 
> manifest.
Disregard - took way longer, but they're back:
Dec 30 16:16:42 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:16:42 mail kernel: sky2 Tx ring pending=72...74 report=73 done=73
Dec 30 16:16:42 mail kernel: 72: 0x0: 0xb18a00be(8490)
Dec 30 16:16:42 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:16:42 mail kernel: sky2 Tx ring pending=86...88 report=87 done=88
Dec 30 16:16:42 mail kernel: 86: 0x0: 0xb1a140be(9014)
Dec 30 16:16:58 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:16:58 mail kernel: sky2 Tx ring pending=50...52 report=51 done=52
Dec 30 16:16:58 mail kernel: 50: 0x0: 0xac27c0be(8490)
Dec 30 16:17:15 mail kernel: sky2 0000:06:00.0: error interrupt status=0x8
Dec 30 16:17:15 mail kernel: sky2 Tx ring pending=16...18 report=16 done=17
Dec 30 16:17:15 mail kernel: 16: 0x0: 0xa67ec0be(8490)
Dec 30 16:17:15 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:17:15 mail kernel: sky2 Tx ring pending=122...124 report=123 
done=124
Dec 30 16:17:15 mail kernel: 122: 0x0: 0xa68980be(8490)
Dec 30 16:17:16 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:17:16 mail kernel: sky2 Tx ring pending=66...68 report=67 done=67
Dec 30 16:17:16 mail kernel: 66: 0x0: 0xa67200be(8490)
Dec 30 16:17:16 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:17:16 mail kernel: sky2 Tx ring pending=74...76 report=75 done=76
Dec 30 16:17:16 mail kernel: 74: 0x0: 0xa659c0be(8490)
Dec 30 16:17:21 mail dhcpd: DHCPINFORM from 10.0.0.11 via eth0
Dec 30 16:17:21 mail dhcpd: DHCPACK to 10.0.0.11 (00:1a:92:8d:30:81) via 
eth0
Dec 30 16:18:01 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:18:01 mail kernel: sky2 Tx ring pending=0...2 report=1 done=1
Dec 30 16:18:01 mail kernel: 0: 0x0: 0x926580be(8490)
Dec 30 16:18:04 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:18:04 mail kernel: sky2 Tx ring pending=116...118 report=117 
done=117
Dec 30 16:18:04 mail kernel: 116: 0x0: 0x91f380be(8490)
Dec 30 16:18:04 mail kernel: sky2 0000:06:00.0: error interrupt status=0x8
Dec 30 16:18:04 mail kernel: sky2 Tx ring pending=102...104 report=102 
done=103
Dec 30 16:18:04 mail kernel: 102: 0x0: 0x91ed80be(8490)
Dec 30 16:18:05 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:18:05 mail kernel: sky2 Tx ring pending=64...68 report=65 done=68
Dec 30 16:18:05 mail kernel: 64: 0x0: 0x91d340be(8490)
Dec 30 16:18:05 mail kernel: 66: 0x0: 0x920040ca(105)
Dec 30 16:18:06 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:18:06 mail kernel: sky2 Tx ring pending=82...86 report=83 done=83
Dec 30 16:18:06 mail kernel: 82: 0x0: 0x91bf80be(9014)
Dec 30 16:18:06 mail kernel: 84: 0x0: 0x91bec0be(7518)
Dec 30 16:18:06 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:18:06 mail kernel: sky2 Tx ring pending=83...86 report=85 done=86
Dec 30 16:18:06 mail kernel: 82: 0x0: 0x91bf80be(9014)
Dec 30 16:18:06 mail kernel: 84: 0x0: 0x91bec0be(7518)
Dec 30 16:18:06 mail kernel: sky2 0000:06:00.0: error interrupt 
status=0x40000008
Dec 30 16:18:06 mail kernel: sky2 Tx ring pending=85...88 report=87 done=87
Dec 30 16:18:06 mail kernel: 84: 0x0: 0x91bec0be(7518)
Dec 30 16:18:06 mail kernel: 86: 0x0: 0x91b080be(8398)
Dec 30 16:18:08 mail kernel: sky2 0000:06:00.0: error interrupt status=0x8
Dec 30 16:18:08 mail kernel: sky2 Tx ring pending=28...30 report=28 done=29
Dec 30 16:18:08 mail kernel: 28: 0x0: 0x919500be(8506)
... continues ...
>>
>> On 12/30/2009 2:15 PM, Michael Breuer wrote:
>>> And now looking at audit.c it seems reasonable that there is a race 
>>> condition when auditd is started at roughly the same time as X. I'm 
>>> guessing that the kaudit thread is fired up; the tty connected; and 
>>> at the same time X grabs the tty. Somewhere in there an skb gets 
>>> hosed and is then reused by whatever comes along - in my case sky2 
>>> as that's where the subsequent demand is. If the demand happens 
>>> first, the contaminated skb (dk in what way yet) is probably waiting 
>>> to manifest as some other bug that's been frustrating people.
>>> On 12/30/2009 12:49 PM, Michael Breuer wrote:
>>>> On 12/30/2009 2:58 AM, Stephen Hemminger wrote:
>>>>> On Wed, 30 Dec 2009 02:23:20 -0500
>>>>> Michael Breuer<mbreuer@...jas.com>  wrote:
>>>>>
>>>>>> Ok - I called dump_txring from sky2_net_intr:
>>>>>> --- a/drivers/net/sky2.c
>>>>>> +++ b/drivers/net/sky2.c
>>>>>> @@ -2725,8 +2791,10 @@ static void sky2_watchdog(unsigned long arg)
>>>>>>    /* Hardware/software error handling */
>>>>>>    static void sky2_err_intr(struct sky2_hw *hw, u32 status)
>>>>>>    {
>>>>>> -       if (net_ratelimit())
>>>>>> +       if (net_ratelimit()) {
>>>>>>                   dev_warn(&hw->pdev->dev, "error interrupt
>>>>>> status=%#x\n", status);
>>>>>> +               dump_txring(hw, 0);
>>>>>> +       }
>>>>>>
>>>>>>           if (status&  Y2_IS_HW_ERR)
>>>>>>                   sky2_hw_intr(hw);
>>>>>>
>>>>>> And got this:
>>>>>> Dec 30 02:17:23 mail kernel: sky2 0000:06:00.0: error interrupt
>>>>>> status=0x40000008
>>>>>> Dec 30 02:17:23 mail kernel: sky2 0000:06:00.0: error interrupt
>>>>>> status=0x40000008
>>>>>> Dec 30 02:17:23 mail kernel: sky2 Tx ring pending=28...30 
>>>>>> report=29 done=29
>>>>>> Dec 30 02:17:23 mail kernel: sky2 Tx ring pending=28...30 
>>>>>> report=29 done=29
>>>>>> Dec 30 02:17:23 mail kernel: sky2 0000:06:00.0: error interrupt 
>>>>>> status=0x8
>>>>>> Dec 30 02:17:23 mail kernel: sky2 0000:06:00.0: error interrupt 
>>>>>> status=0x8
>>>>>> Dec 30 02:17:23 mail kernel: sky2 Tx ring pending=30...32 
>>>>>> report=30 done=31
>>>>>> Dec 30 02:17:23 mail kernel: sky2 Tx ring pending=30...32 
>>>>>> report=30 done=31
>>>>>>
>>>>> I notice that you have NOUVEAU Nvidia drivers loaded? The one 
>>>>> difference in HW
>>>>> between your board and mine is that I have ATI video card.
>>>>>
>>>> Seems the problem is linked to auditd and X11 (but not nouveau).
>>>>
>>>> Today, I ran a bunch of scenarios. I first determined that the 
>>>> problem only manifest in runlevel 5. Next, this occurred with or 
>>>> without KMS and with or without nouveau. This happened whether or 
>>>> not I was logged in (local or remote), and regardless of window 
>>>> manager (xdm, gdm, kdm). I then checked to see what else was 
>>>> different between runlevel 3 and 5 - only thing was auditd. I 
>>>> disabled auditd and reran - no errors.
>>>>
>>>> Now for the odd stuff:
>>>>
>>>> The errors only manifest if the high throughput data transfer is 
>>>> initiated when the system is in runlevel 5 and auditd was started 
>>>> by init when transitioning from runlevel 3 to 5. For example, the 
>>>> following scenarios do not cause the errors to manifest:
>>>>
>>>> runlevel3; start auditd runlevel 5; start transfer
>>>> runlevel3; chkconfig auditd off; runlevel5; start auditd; start 
>>>> transfer
>>>> runlevel3; start transfer (note: errors do not occur if I 
>>>> transition to runlevel 5 after the high bandwidth transfer has 
>>>> started)
>>>> runlevel3; startx; start transfer
>>>>
>>>> The only way I get the problem to manifest is transition to 
>>>> runlevel 5 with chkconfig auditd on (level 5 only) and then initate 
>>>> the windows backup.
>>>>
>>>> I'm guessing that there is some sort of race condition happening 
>>>> between X (xdm/gdm/kdm/greeter?) and auditd that is somehow 
>>>> corrupting something. I'd hazard a more or less obvious guess that 
>>>> whatever's being corrupted differs when there is already a high 
>>>> throughput transfer under way.
>>>>
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>>>
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>>
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