From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752647Ab0CXVU5 (ORCPT ); Wed, 24 Mar 2010 17:20:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40310 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342Ab0CXVU4 (ORCPT ); Wed, 24 Mar 2010 17:20:56 -0400 Date: Wed, 24 Mar 2010 22:19:24 +0100 From: Andrea Arcangeli To: Jonathan Corbet Cc: Andrew Morton , Mel Gorman , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 07/11] Memory compaction core Message-ID: <20100324211924.GH10659@random.random> References: <1269347146-7461-1-git-send-email-mel@csn.ul.ie> <1269347146-7461-8-git-send-email-mel@csn.ul.ie> <20100324133347.9b4b2789.akpm@linux-foundation.org> <20100324145946.372f3f31@bike.lwn.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100324145946.372f3f31@bike.lwn.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jonathan, On Wed, Mar 24, 2010 at 02:59:46PM -0600, Jonathan Corbet wrote: > On Wed, 24 Mar 2010 13:33:47 -0700 > Andrew Morton wrote: > > > > + VM_BUG_ON(cc == NULL); > > > > It's a bit strange to test this when we're about to oops anyway. The > > oops will tell us the same thing. > > ...except that we've seen a fair number of null pointer dereference > exploits that have told us something altogether different. Are we > *sure* we don't want to test for null pointers...? Examples? Maybe WARN_ON != oops, but VM_BUG_ON still an oops that is and without serial console it would go lost too. I personally don't see how it's needed. Plus those things are mostly for debug to check for invariant condition, how long it takes to sort it out isn't very relevant. So I'm on Andrew camp ;).