From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58EECC3B185 for ; Mon, 17 Feb 2020 10:20:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DFD420679 for ; Mon, 17 Feb 2020 10:20:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729201AbgBQKUU (ORCPT ); Mon, 17 Feb 2020 05:20:20 -0500 Received: from helcar.hmeau.com ([216.24.177.18]:50508 "EHLO deadmen.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726397AbgBQKUT (ORCPT ); Mon, 17 Feb 2020 05:20:19 -0500 Received: from gondobar.mordor.me.apana.org.au ([192.168.128.4] helo=gondobar) by deadmen.hmeau.com with esmtps (Exim 4.89 #2 (Debian)) id 1j3dVg-0005di-3a; Mon, 17 Feb 2020 18:20:16 +0800 Received: from herbert by gondobar with local (Exim 4.89) (envelope-from ) id 1j3dVd-0003kW-1p; Mon, 17 Feb 2020 18:20:13 +0800 Date: Mon, 17 Feb 2020 18:20:13 +0800 From: Herbert Xu To: "Jason A. Donenfeld" Cc: eric.dumazet@gmail.com, cai@lca.pw, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH v3] skbuff: fix a data race in skb_queue_len() Message-ID: <20200217102012.si4t2x75mo52fnlh@gondor.apana.org.au> References: <20200206163844.GA432041@zx2c4.com> <20200217032458.kwatitz3pvxeb25w@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 17, 2020 at 08:39:45AM +0100, Jason A. Donenfeld wrote: > > Not necessarily a big fan of this either, but just for the record here > in case it helps, while you might complain about instruction size > blowing up a bit, cycle-wise these wind up being about the same > anyway. On x86, one instruction != one cycle. I don't care about that. My problem is with the mindless patches that started this thread. Look at the patch: commit 86b18aaa2b5b5bb48e609cd591b3d2d0fdbe0442 Author: Qian Cai Date: Tue Feb 4 13:40:29 2020 -0500 skbuff: fix a data race in skb_queue_len() It's utter garbage. Why on earth did it change that one instance of unix_recvq_full? In fact you can see how stupid it is because right after the call that got changed we again call into unix_recvq_full which surely would trigger the same warning. So far the vast majority of the KCSAN patches that have caught my attention have been of this mindless kind that does not add any value to the kernel. If anything they could be hiding real bugs that would now be harder to find. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt