Re: gianfar.c null pointer deref in gfar_start_xmit().

Le mardi 09 août 2011 à 08:06 -0500, Robin Holt a écrit :

On Tue, Aug 09, 2011 at 09:10:13AM +0200, Eric Dumazet wrote:

quoted

Le mardi 09 août 2011 à 01:54 -0500, Robin Holt a écrit :

quoted

On Tue, Aug 02, 2011 at 09:44:38PM -0500, Robin Holt wrote:

quoted

While using the v3.0 kernel on a Freescale P1010RDB with 3 minor patches
(None which affect gianfar.c), I get a NULL pointer deref at:

static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
...
	regs = tx_queue->grp->regs;

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.

Any suggestions would be welcome.   To reproduce, all I need to do is
a few sequences of pings.

I was able to reproduce this with the net-next-2.6 kernel as well.

This driver incorrectly assumes a non dense txqueue array is possible
for a netdev, but its not true.

In the meantime, you could force it to use one tx_queue only.

tx_queues = (u32 *)of_get_property(np, "fsl,num_tx_queues", NULL);
num_tx_qs = tx_queues ? *tx_queues : 1;

I fixed up the .dts file and now it works.  I have not tested the RGMII
interface yet so I do not know if that supports multiple queues.  I assume
I could find it in the documentation.  What might I be looking for?

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.