netdev - Re: ixgbe warning

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Message-ID: <OF7CCEEFED.46E6EE59-ON65257695.002F98AC-65257695.00303B56@in.ibm.com>
Date:	Wed, 23 Dec 2009 14:28:08 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	David Miller <davem@...emloft.net>,
	e1000-devel@...ts.sourceforge.net, NetDev <netdev@...r.kernel.org>
Subject: Re: ixgbe warning

> Yinghai Lu <yinghai@...nel.org>
>
> >> [  809.824721] WARNING: at net/core/dev.c:1908
> > dev_queue_xmit+0x243/0x4c7()
> >> [  809.832183] Hardware name: Sun
> >> [  809.832193] eth16 selects TX queue 98, but real number of TX queues
is
> > 64
> >> [  809.832203] Modules linked in:
> >> [  809.832216] Pid: 26440, comm: iperf Not tainted
> >> 2.6.33-rc1-tip-yh-00304-g97a015d-dirty #1007
> >> [  809.832221] Call Trace:
> >> [  809.832232]  <IRQ>  [<ffffffff81c14e08>] ?
dev_queue_xmit+0x243/0x4c7
> >> [  809.832266]  [<ffffffff8107a098>] warn_slowpath_common+0x7c/0xa9
> >> [  809.832283]  [<ffffffff8107a11c>] warn_slowpath_fmt+0x41/0x43
> >> [  809.832300]  [<ffffffff81c14e08>] dev_queue_xmit+0x243/0x4c7
> >> [  809.832319]  [<ffffffff81c14d5a>] ? dev_queue_xmit+0x195/0x4c7
> >> [  809.832340]  [<ffffffff81c52e87>] arp_send+0x39/0x3b
> >> [  809.832355]  [<ffffffff81c5384c>] arp_solicit+0x1da/0x1f7
> >> [  809.832376]  [<ffffffff81c1d89d>] neigh_timer_handler+0x243/0x292
> >> [  809.832391]  [<ffffffff81c1d65a>] ? neigh_timer_handler+0x0/0x292
> >> [  809.832411]  [<ffffffff8108844b>] run_timer_softirq+0x265/0x322
> >> [  809.832429]  [<ffffffff810883af>] ? run_timer_softirq+0x1c9/0x322
> >> [  809.832448]  [<ffffffff81098bd3>] ? __run_hrtimer+0x104/0x132
> >> [  809.832471]  [<ffffffff81080909>] __do_softirq+0xee/0x1b9
> >> [  809.832488]  [<ffffffff81034a8c>] call_softirq+0x1c/0x3e
> >> [  809.832499]  [<ffffffff810360e9>] do_softirq+0x3d/0x85
> >> [  809.832516]  [<ffffffff81080492>] irq_exit+0x4a/0x89
> >> [  809.832536]  [<ffffffff81d37afb>]
smp_apic_timer_interrupt+0x8d/0x9b
> >> [  809.832557]  [<ffffffff81034553>] apic_timer_interrupt+0x13/0x20
> >> [  809.832563]  <EOI>  [<ffffffff81068e41>] ? walk_tg_tree+0x0/0xe3
> >> [  809.832594]  [<ffffffff810a6f29>] ? trace_hardirqs_on+0xd/0xf
> >> [  809.832616]  [<ffffffff81d32759>] ? _raw_spin_unlock_irq+0x33/0x36
> >> [  809.832634]  [<ffffffff81d2fc12>] schedule+0x7a2/0x83d
> >> [  809.832649]  [<ffffffff81d32756>] ? _raw_spin_unlock_irq+0x30/0x36
> >> [  809.832666]  [<ffffffff81d31b97>] __down_read+0x97/0xc4
> >> [  809.832674]  [<ffffffff81d311c7>] down_read+0x6d/0x81
> >> [  809.832684]  [<ffffffff81d3539e>] ? do_page_fault+0x1bb/0x31d
> >> [  809.832699]  [<ffffffff81d3539e>] do_page_fault+0x1bb/0x31d
> >> [  809.832716]  [<ffffffff81d32c7f>] page_fault+0x1f/0x30
> >> [  809.832726] ---[ end trace 9c325e35daa3e5c8 ]---
> >
> > I guess you are running on a big SMP system? If so,
> > ixgbe_select_queue() is not limiting the queue_index
> > based on real_num_tx_queues, and possibly returning
> > a bad txq from:
> >
> >       if (adapter->flags & IXGBE_FLAG_FDIR_HASH_CAPABLE)
> >             return txq;
> >
> > Also, I was looking at other providers of select_queue and found:
> >
> > u16 gfar_select_queue(struct net_device *dev, struct sk_buff *skb)
> > {
> >         return skb_get_queue_mapping(skb);
> > }
> >
> > How can this be correct (driver supports upto 8 txq's). Unless txq=0
for
> > xmits of all locally
> > generated packets is fine.
>
> may need this one...
>
> ---
>  drivers/net/ixgbe/ixgbe_main.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6/drivers/net/ixgbe/ixgbe_main.c
> ===================================================================
> --- linux-2.6.orig/drivers/net/ixgbe/ixgbe_main.c
> +++ linux-2.6/drivers/net/ixgbe/ixgbe_main.c
> @@ -5317,7 +5317,7 @@ static int ixgbe_maybe_stop_tx(struct ne
>  static u16 ixgbe_select_queue(struct net_device *dev, struct sk_buff
*skb)
>  {
>     struct ixgbe_adapter *adapter = netdev_priv(dev);
> -   int txq = smp_processor_id();
> +   int txq = smp_processor_id() % adapter->num_tx_queues;
>
>     if (adapter->flags & IXGBE_FLAG_FDIR_HASH_CAPABLE)
>        return txq;

The modulo operation is not required (and costly too) for
other cases. You should move it inside the if case, or I
guess Jeff can suggest the right fix.

thanks,

- KK

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