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From: David Miller <davem@davemloft.net>
Subject: Re: ~3 hours old git tree: Virtual device lo asks to queue packet!
Date: Fri, 20 Jul 2007 19:47:43 -0700 (PDT)
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From: Patrick McHardy <kaber@trash.net>
Date: Thu, 19 Jul 2007 12:11:10 +0200

> The easiest fix would be to use egress_subqueue[1] in struct
> net_device, but I think that may cause warnings with newer gccs
> when using a constant index that is > 0. OTOH using constant
> indices doesn't seem to make much sense for the subqueue array.
> 
> Arkadiusz, does this patch fix the problem?

I've applied this, but long term we should either:

1) Make loopback_dev dynamically allocated just like every
   other netdev, so make loopback_init() a postcore_initcall()
   to make sure that is setup early enough.

   Then have to walk over the tree making everything able
   to handle the fact that it's a pointer.  Several data
   structures are compile time initialized to "&loopback_dev"
   for example, and therefore will have to be transformed into
   a run-time initialization.

2) Pick some arbitrary limit for the queues, and just have that
   many of them allocated in every netdev.

I like #2 because it allows us to get back the netdev_priv()
optimization.