linux-kernel - Re: WARNING: at net/sched/sch_generic.c:219 dev

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Message-ID: <20081126225421.GA8906@xw6200.broadcom.net>
Date:	Wed, 26 Nov 2008 14:54:21 -0800
From:	"Matt Carlson" <mcarlson@...adcom.com>
To:	"Willy Tarreau" <w@....eu>
cc:	"Matthew Carlson" <mcarlson@...adcom.com>,
	"Roger Heflin" <rogerheflin@...il.com>,
	"Peter Zijlstra" <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: WARNING: at net/sched/sch_generic.c:219
 dev_watchdog+0xfe/0x17e() with tg3 network

On Wed, Nov 26, 2008 at 01:12:20PM -0800, Willy Tarreau wrote:
> Hi Matt,
> 
> On Tue, Nov 25, 2008 at 09:54:13AM -0800, Matt Carlson wrote:
> > On Mon, Nov 24, 2008 at 09:31:28PM -0800, Willy Tarreau wrote:
> > > On Mon, Nov 24, 2008 at 05:52:23PM -0800, Matt Carlson wrote:
> > > (...)
> > > > > tg3: eth0: transmit timed out, resetting
> > > > > tg3: DEBUG: MAC_TX_STATUS[0000000b] MAC_RX_STATUS[00000006]
> > > > > tg3: DEBUG: RDMAC_STATUS[00000000] WDMAC_STATUS[00000008]
> > > > > tg3: tg3_stop_block timed out, ofs=1400 enable_bit=2
> > > > > tg3: tg3_stop_block timed out, ofs=c00 enable_bit=2
> > > > > tg3: tg3_stop_block timed out, ofs=4c00 enable_bit=2
> > > > > tg3: eth0: Link is down.
> > > > > tg3: eth0: Link is up at 100 Mbps, full duplex.
> > > > > tg3: eth0: Flow control is on for TX and on for RX.
> > > > > 
> > > > > The ease with which I reproduce it here clearly indicates that this is
> > > > > related to the switch, probably just the fact that it is at 100 Mbps.
> > > > > Unfortunately this evening I must go, but I still have one 100 Mbps
> > > > > switch somewhere at home, I'll reproduce the same test ASAP in order
> > > > > to bisect the issue.
> > > > > 
> > > > > Regards,
> > > > > Willy
> > > > 
> > > > Does turning off flow control help at all?
> > > 
> > > I have not tested but I will. I hope to be able to trigger the problem
> > > on other similar switches, because I'm only once a week connected to
> > > the culprit...
> > 
> > I can't say for certain, but I suspect the problem might be more
> > associated with the link speed than the particular switch you are using.
> > Can you try autoneg'ing down to a slower speed and see if that helps
> > make the problem more reproducable?
> 
> I've run a new test on a switch I have here at home (another el-cheapo,
> non-manageable 100 Mbps, netgear this time). Unfortunately I cannot
> reproduce the problem at all. I have disabled FC on my laptop, it did
> not have any effect.

Disabling FC should have a positive effect, not a negative one.  It
might be the case that the switch does not advertise nor support FC.  If
that is true, you might not be able to repro the problem no matter what
you did (if your problem is what I think it is).  Can you check your
link messages and see if it really is negotiated to off?  (I see the
message above, but I don't think that is with the current switch.)

> I have disabled auto-neg and manually forced the
> speed to 100/Full on my laptop, and could not reproduce the problem
> either (though the speed was much lower due to the switch obviously
> negociating 100/Half when not seeing my NWay frames).

Yes.  If you force the link, both sides must be forced.  The switch
rightly assumes HD when bringing the link up.

> I have tried unplugging the cable during transfers and changing negociation
> during transfers, trying to trigger artifacts, but with no result. So I
> think that I will really need to debug this on the "faulty" switch on
> next monday.  It does not surprize me much, because we don't see that
> many reports for a similar problem, eventhough the tg3 is very common
> in laptops. I just hope it's a recent regression, as I'd prefer avoid
> having to bisect from a very old kernel.
> 
> I'll keep you informed,
> Willy

O.K.


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