Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759095AbYFQSev (ORCPT ); Tue, 17 Jun 2008 14:34:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755961AbYFQSen (ORCPT ); Tue, 17 Jun 2008 14:34:43 -0400 Received: from extu-mxob-1.symantec.com ([216.10.194.28]:45889 "EHLO extu-mxob-1.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754756AbYFQSem (ORCPT ); Tue, 17 Jun 2008 14:34:42 -0400 Date: Tue, 17 Jun 2008 19:33:32 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.site To: Lee Schermerhorn cc: Daisuke Nishimura , Andrew Morton , Rik van Riel , Kosaki Motohiro , Nick Piggin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org Subject: Re: [PATCH][RFC] fix kernel BUG at mm/migrate.c:719! in 2.6.26-rc5-mm3 In-Reply-To: <1213724798.8707.41.camel@lts-notebook> Message-ID: References: <20080611225945.4da7bb7f.akpm@linux-foundation.org> <20080617163501.7cf411ee.nishimura@mxp.nes.nec.co.jp> <1213724798.8707.41.camel@lts-notebook> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 816 Lines: 19 On Tue, 17 Jun 2008, Lee Schermerhorn wrote: > > Now I wonder if the assertion that newpage count == 1 could be violated? > I don't see how. We've just allocated and filled it and haven't > unlocked it yet, so we should hold the only reference. Do you agree? Disagree: IIRC, excellent example of the kind of assumption that becomes invalid with Nick's speculative page references. Someone interested in the previous use of the page may have incremented the refcount, and in due course will find that it's got reused for something else, and will then back off. Hugh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/