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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 8DFE9C46475 for ; Mon, 5 Nov 2018 10:41:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DFCE20869 for ; Mon, 5 Nov 2018 10:41:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Wv+odmWP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4DFCE20869 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729158AbeKEUAx (ORCPT ); Mon, 5 Nov 2018 15:00:53 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:54744 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726932AbeKEUAw (ORCPT ); Mon, 5 Nov 2018 15:00:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=xM+5KMmwXYKR9Dl+Z8QkTOny5tVl3Bw3ZbxUOoCyscc=; b=Wv+odmWPtgTZFNxPoRYeWsf1q zALPW7CCk8mgrIshGlbTfXFUH+25v16P/rUnrQRVFSzQJ//1lz+BJ744NjhIuXEOcIX4xEluFRcrz RjBK/tXUJeoZmyrfmn9hjrteIoFTY/tbkBT/4VKv2LaKMUL5PkLTw/Mv7Y112A8+LzfDpD5ICbXUf XU3qgzXhjmHnMMngQ1C8LfBpxSWLFHgYG1P9w81QthqXS1OQpnFoWX4lMUTr/bM9+dyqHy1op+5aq 30eYLR1Ig9byueGRzHCuZ9o/lmTSO7Y9hZ9OO8ulQG0sO47Dg9Q42bI+KUkaNO3o7An//O2a4ecaO Tiw6aeszA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gJcHb-0002gD-BL; Mon, 05 Nov 2018 10:38:59 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B1FB72029F9FF; Mon, 5 Nov 2018 11:38:57 +0100 (CET) Date: Mon, 5 Nov 2018 11:38:57 +0100 From: Peter Zijlstra To: Andrey Ryabinin Cc: Trond Myklebust , "mark.rutland@arm.com" , "linux-kernel@vger.kernel.org" , "ralf@linux-mips.org" , "jlayton@kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "bfields@fieldses.org" , "linux-mips@linux-mips.org" , "linux@roeck-us.net" , "linux-nfs@vger.kernel.org" , "akpm@linux-foundation.org" , "will.deacon@arm.com" , "boqun.feng@gmail.com" , "paul.burton@mips.com" , "anna.schumaker@netapp.com" , "jhogan@kernel.org" , "netdev@vger.kernel.org" , "davem@davemloft.net" , "arnd@arndb.de" , "paulus@samba.org" , "mpe@ellerman.id.au" , "benh@kernel.crashing.org" , Paul McKenney , dvyukov@google.com Subject: Re: [RFC PATCH] lib: Introduce generic __cmpxchg_u64() and use it where needed Message-ID: <20181105103857.GB22431@hirez.programming.kicks-ass.net> References: <1541015538-11382-1-git-send-email-linux@roeck-us.net> <20181031213240.zhh7dfcm47ucuyfl@pburton-laptop> <20181031220253.GA15505@roeck-us.net> <20181031233235.qbedw3pinxcuk7me@pburton-laptop> <4e2438a23d2edf03368950a72ec058d1d299c32e.camel@hammerspace.com> <20181101131846.biyilr2msonljmij@lakrids.cambridge.arm.com> <20181101145926.GE3178@hirez.programming.kicks-ass.net> <20181101163212.GF3159@hirez.programming.kicks-ass.net> <5a846924-e642-d9d1-4e0e-810bd4d01c26@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5a846924-e642-d9d1-4e0e-810bd4d01c26@virtuozzo.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, Nov 02, 2018 at 07:19:15PM +0300, Andrey Ryabinin wrote: > UBSAN warns about signed overflows despite -fno-strict-overflow if gcc > version is < 8. I have learned recently that UBSAN in GCC 8 ignores > signed overflows if -fno-strict-overflow of fwrapv is used. Ah, good. > We can always just drop -fsanitize=signed-integer-overflow if it considered too noisy. I think that is the most consistent beahviour. signed overflow is not UB in the kernel. > Although it did catch some real bugs. If we want an over/under-flow checker, then that should be a separate plugin and not specific to signed or unsigned.