Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758124AbYH1VAc (ORCPT ); Thu, 28 Aug 2008 17:00:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756479AbYH1VAB (ORCPT ); Thu, 28 Aug 2008 17:00:01 -0400 Received: from py-out-1112.google.com ([64.233.166.179]:22741 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754264AbYH1VAA (ORCPT ); Thu, 28 Aug 2008 17:00:00 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=XNxPvKb6ifzB1ZhQlwCnZF+DIiw06UU/cBBcvvb4f5dhjQDAAVdu93oW7mDR8b4GRD tKQg/NvtvSwTJOtTavA29oruaMFS1o/vQ39NcM6GKJK9H64F2edLI/d9hV7haExBNitz jLeunaG2AFrBQnllwTBbVfFGzFpk2mo49Bvp4= Message-ID: <19f34abd0808281359p6ee01393x209f2bf2de3918af@mail.gmail.com> Date: Thu, 28 Aug 2008 22:59:59 +0200 From: "Vegard Nossum" To: "Adrian Bunk" Subject: Re: [RFC][PATCH] bitfields API Cc: "Pekka Enberg" , "Alexey Dobriyan" , "David Miller" , "Ingo Molnar" , "Andrew Morton" , linux-kernel@vger.kernel.org In-Reply-To: <20080828202750.GB16462@cs181140183.pp.htv.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080828183223.GA30781@localhost.localdomain> <20080828184025.GA22165@x200.localdomain> <48B6F12F.1010909@cs.helsinki.fi> <20080828202750.GB16462@cs181140183.pp.htv.fi> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1669 Lines: 44 On Thu, Aug 28, 2008 at 10:27 PM, Adrian Bunk wrote: > On Thu, Aug 28, 2008 at 09:40:47PM +0300, Pekka Enberg wrote: >> Hi Alexey, >> >> Alexey Dobriyan wrote: >>> On Thu, Aug 28, 2008 at 08:32:23PM +0200, Vegard Nossum wrote: >>>> How do you feel about this patch? It's all about making kmemcheck more >>>> useful... and not much else. Does it have any chance of entering the >>>> kernel along with kmemcheck (when/if that happens)? >>> >>> DEFINE_BITFIELD is horrible. >> >> Heh, heh, one alternative is to have a kmemcheck_memset() thingy that >> unconditionally zeroes bit fields and maybe is a no-op when kmemcheck is >> disabled. > > This sounds as if this might cause bugs to disappear when debugging gets > turned on? > > Or do I miss anything? You are correct :-) Almost all the possible solutions (at least the feasible ones) are trade-offs between false-positives and false-negatives. So here we are trading a bunch of false-positive errors (a couple of thousand for transferring a 1M file over ssh :-)) for detecting any code that uses an uninitialized flag in struct skbuff. So in this case it is more useful to hide reports about this single bit-field. Vegard -- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036 -- 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/