From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: gianfar.c null pointer deref in gfar_start_xmit().
Date: Wed, 10 Aug 2011 08:01:01 +0200
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References: <20110803024438.GH4926@sgi.com> <20110809065407.GF3709@sgi.com>
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Cc: Sandeep Gopalpet <Sandeep.Kumar@freescale.com>,
	"David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org
To: Robin Holt <holt@sgi.com>
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Le mardi 09 ao=C3=BBt 2011 =C3=A0 08:06 -0500, Robin Holt a =C3=A9crit =
:
> On Tue, Aug 09, 2011 at 09:10:13AM +0200, Eric Dumazet wrote:
> > Le mardi 09 ao=C3=BBt 2011 =C3=A0 01:54 -0500, Robin Holt a =C3=A9c=
rit :
> > > On Tue, Aug 02, 2011 at 09:44:38PM -0500, Robin Holt wrote:
> > > >=20
> > > > While using the v3.0 kernel on a Freescale P1010RDB with 3 mino=
r patches
> > > > (None which affect gianfar.c), I get a NULL pointer deref at:
> > > >=20
> > > > static int gfar_start_xmit(struct sk_buff *skb, struct net_devi=
ce *dev)
> > > > {
> > > > ...
> > > > 	regs =3D tx_queue->grp->regs;
> > > >=20
> > > > I put a BUG_ON(tx_queue->grp) just before this line and it did =
trip.
> > > > I have not looked at this any more than that.
> > > >=20
> > > > Any suggestions would be welcome.   To reproduce, all I need to=
 do is
> > > > a few sequences of pings.
> > >=20
> > > I was able to reproduce this with the net-next-2.6 kernel as well=
=2E
> > >=20
> >=20
> > This driver incorrectly assumes a non dense txqueue array is possib=
le
> > for a netdev, but its not true.
> >=20
> > In the meantime, you could force it to use one tx_queue only.
> >=20
> > tx_queues =3D (u32 *)of_get_property(np, "fsl,num_tx_queues", NULL)=
;
> > num_tx_qs =3D tx_queues ? *tx_queues : 1;
>=20
> I fixed up the .dts file and now it works.  I have not tested the RGM=
II
> interface yet so I do not know if that supports multiple queues.  I a=
ssume
> I could find it in the documentation.  What might I be looking for?
>=20

What exact change did you in dts ?

Assuming your p1010rdb is single core powerpc, I fail to see why 8
queues should be enabled on NIC. It only increases number of interrupts
if multiple flows are in use, and memory footprint.