linux-kernel - Re: WARNING: at net/core/dev.c:2161 net_rx

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Date:	Tue, 16 Oct 2007 00:03:57 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	David Miller <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	shemminger@...ux-foundation.org, Jeff Garzik <jgarzik@...ox.com>
Subject: Re: WARNING: at net/core/dev.c:2161 net_rx_action()

* David Miller <davem@...emloft.net> wrote:

> From: Ingo Molnar <mingo@...e.hu>
> Date: Mon, 15 Oct 2007 13:24:30 +0200
> 
> > got this warning with Linus' latest -git tree:
> > 
> >   WARNING: at net/core/dev.c:2161 net_rx_action()
> >    [<80564db4>] net_rx_action+0xce/0x186
> >    [<8011ba98>] __do_softirq+0x6c/0xcf
> >    [<8011bb2d>] do_softirq+0x32/0x36
> >    [<8011bcae>] irq_exit+0x35/0x40
> >    [<80104fdb>] do_IRQ+0x5c/0x71
> >    [<801048cd>] do_nmi+0x8f/0x238
> >    [<801033a3>] common_interrupt+0x23/0x30
> >    =======================
> 
> This is a driver bug, the work "budget" passed into a driver's 
> ->poll() handler should never be exceeded.  That's what this warning 
> assertion is checking.
> 
> What ethernet card is in your system and what driver is being used to 
> drive it?

it's forcedeth.

i've checked nv_napi_poll(), and i dont see how it could return larger 
than 'limit' number of packets.

it could return packets == limit though:

                pkts = nv_rx_process_optimized(dev, budget);
...

        if (pkts < budget) {
                /* re-enable receive interrupts */
                spin_lock_irqsave(&np->lock, flags);

                __netif_rx_complete(dev, napi);

...
        return pkts;

shouldnt that be "pkts <= budget"? But even that shouldnt cause a larger 
than limit return. Weird.

there are two networking cards in the system, the other one is a:

  eth1: RealTek RTL8139 at 0xf080e000, 00:c0:df:03:68:5d, IRQ 11
  eth1:  Identified 8139 chip type 'RTL-8139B'

but this one should be inactive (not plugged into the network). Should i 
try to get a debug print out of the actual 'weight' and 'work' integers, 
and of the n->poll function address?

	Ingo
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