Re: [RFC][PATCH 2/9] deadlock prevention core

From: Peter Zijlstra
Date: Thu Aug 10 2006 - 02:28:16 EST

On Wed, 2006-08-09 at 16:58 -0700, David Miller wrote:
> From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Date: Wed, 09 Aug 2006 16:07:20 +0200
> > Hmm, what does sk_buff::input_dev do? That seems to store the initial
> > device?
> You can run grep on the tree just as easily as I can which is what I
> did to answer this question. It only takes a few seconds of your
> time to grep the source tree for things like "skb->input_dev", so
> would you please do that before asking more questions like this?

That is exactly what I did, but I wanted a bit of confirmation. Sorry if
offends you, but I'm a bit new to this network thing.

> It does store the initial device, but as Thomas tried so hard to
> explain to you guys these device pointers in the skb are transient and
> you cannot refer to them outside of packet receive processing.

Yes, I understood that after Thomas' last mail.

> The reason is that there is no refcounting performed on these devices
> when they are attached to the skb, for performance reasons, and thus
> the device can be downed, the module for it removed, etc. long before
> the skb is freed up.

I understood that, thanks.

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