From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [RFC][PATCH 2/9] deadlock prevention core Date: Thu, 10 Aug 2006 08:25:59 +0200 Message-ID: <1155191159.12225.108.camel@twins> References: <44D976E6.5010106@google.com> <20060809131942.GY14627@postel.suug.ch> <1155132440.12225.70.camel@twins> <20060809.165846.107940575.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: tgraf@suug.ch, phillips@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from amsfep19-int.chello.nl ([213.46.243.16]:12142 "EHLO amsfep17-int.chello.nl") by vger.kernel.org with ESMTP id S1161060AbWHJGai (ORCPT ); Thu, 10 Aug 2006 02:30:38 -0400 To: David Miller In-Reply-To: <20060809.165846.107940575.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, 2006-08-09 at 16:58 -0700, David Miller wrote: > From: Peter Zijlstra > 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 it 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.