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

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Message-ID: <20071015220720.GA16101@elte.hu>
Date:	Tue, 16 Oct 2007 00:07:20 +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()


* Ingo Molnar <mingo@...e.hu> wrote:

> > 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?

ok, i've added such a patch.

looking at the dev.c code - can napi_struct->weight be zero 
legitimately? If yes then the 0 gets passed to the driver and the driver 
would return 1 - violating the assertion.

	Ingo
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