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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8DBDEC433DF for ; Wed, 1 Jul 2020 15:05:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70BA720760 for ; Wed, 1 Jul 2020 15:05:24 +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="i74sl3ZO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731687AbgGAPFW (ORCPT ); Wed, 1 Jul 2020 11:05:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731039AbgGAPFV (ORCPT ); Wed, 1 Jul 2020 11:05:21 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E9C0C08C5C1; Wed, 1 Jul 2020 08:05:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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; bh=yjUbAZQQ9f4rcShW5GkixqYv9x2nD42GGzyjdsiFm50=; b=i74sl3ZOPr1xqJIhkMJglGWOkB U8dqkz+3Y5fKVBDLcgGRCYbTPQFBGPgHtaCMun69vkwL/Ry/Z+4Jsl8Mf+SEd1g2rFtmyvmpbWIYZ K0Ycyjqzo60JLazLm+uQfh7KsY8FqjTzInhLzUzA/uu1WwZ1uS4jmIhsjRK2swdHfjsLC2mBUqXmb tjLVkf7OGf4kz+DTg9+2SwJMjK14kVHRsmKF/8JUPsny87vwFakQlM7eTrs35Vus1k5vP28RmJNHc Yyq+PGlJEHTv7w05Krc9LSs+q+qVge1miTYAIcksAas9z16JswYUyikbLlMyiWZjWWnmMZFBaj5Bf 7m/rqxmg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqeIU-0005dy-9r; Wed, 01 Jul 2020 15:05:14 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 229A930015A; Wed, 1 Jul 2020 17:05:12 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1242023D44E56; Wed, 1 Jul 2020 17:05:12 +0200 (CEST) Date: Wed, 1 Jul 2020 17:05:12 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Marco Elver , Nick Desaulniers , Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , LKML , linux-pci@vger.kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200701150512.GH4817@hirez.programming.kicks-ass.net> References: <20200625080313.GY4817@hirez.programming.kicks-ass.net> <20200625082433.GC117543@hirez.programming.kicks-ass.net> <20200625085745.GD117543@hirez.programming.kicks-ass.net> <20200630191931.GA884155@elver.google.com> <20200630201243.GD4817@hirez.programming.kicks-ass.net> <20200630203016.GI9247@paulmck-ThinkPad-P72> <20200701114027.GO4800@hirez.programming.kicks-ass.net> <20200701140654.GL9247@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200701140654.GL9247@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 01, 2020 at 07:06:54AM -0700, Paul E. McKenney wrote: > The current state in the C++ committee is that marking variables > carrying dependencies is the way forward. This is of course not what > the Linux kernel community does, but it should not be hard to have a > -fall-variables-dependent or some such that causes all variables to be > treated as if they were marked. Though I was hoping for only pointers. > Are they -sure- that they -absolutely- need to carry dependencies > through integers??? What's 'need'? :-) I'm thinking __ktime_get_fast_ns() is better off with a dependent load than it is with an extra smp_rmb(). Yes we can stick an smp_rmb() in there, but I don't like it. Like I wrote earlier, if I wanted a control dependency, I'd have written one. 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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 02901C433DF for ; Wed, 1 Jul 2020 15:06:42 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CBD95206C3 for ; Wed, 1 Jul 2020 15:06:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="PVh21AEZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBD95206C3 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-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=kRLrdDE6XQ/jKAr/v+eOQTw3nRsYIH+GTMqNyw4FlzE=; b=PVh21AEZCJhq4YQhZH5TAktCp LbfksLMhaHj3cqUjllC6IyfCKAXefaGVC2t2JjePJvy/caL1c10CtnRTUjcIEFBmPE588v3ib4zYu 7TrXo5YwuLDy0kYmgY4bHPujHyAUvOGoHJ8DsagRIHtndnDZhwTHg4ZOfUGUmzOuhFxcibjmXnB3A MK2U62hDXUYloNm2vWXLUKBiKKH+3j6RNgFdrM+gAoRMOP8vBK3eIgTI8iau+6Iiu4r8oxdR1yzpC YSs1YR/Z3c7A+3rMgPz1umr4dUvS0uD1FwtrowV0DnDdTaUQpancOAapZmpfAQczCCj+cdiPJqR6R 9Ln8RL3vg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqeIV-0005eC-TR; Wed, 01 Jul 2020 15:05:15 +0000 Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqeIU-0005dy-9r; Wed, 01 Jul 2020 15:05:14 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 229A930015A; Wed, 1 Jul 2020 17:05:12 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1242023D44E56; Wed, 1 Jul 2020 17:05:12 +0200 (CEST) Date: Wed, 1 Jul 2020 17:05:12 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200701150512.GH4817@hirez.programming.kicks-ass.net> References: <20200625080313.GY4817@hirez.programming.kicks-ass.net> <20200625082433.GC117543@hirez.programming.kicks-ass.net> <20200625085745.GD117543@hirez.programming.kicks-ass.net> <20200630191931.GA884155@elver.google.com> <20200630201243.GD4817@hirez.programming.kicks-ass.net> <20200630203016.GI9247@paulmck-ThinkPad-P72> <20200701114027.GO4800@hirez.programming.kicks-ass.net> <20200701140654.GL9247@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200701140654.GL9247@paulmck-ThinkPad-P72> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Marco Elver , "maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , Kees Cook , Kernel Hardening , Greg Kroah-Hartman , Masahiro Yamada , Linux Kbuild mailing list , Nick Desaulniers , LKML , clang-built-linux , Sami Tolvanen , linux-pci@vger.kernel.org, Will Deacon , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 01, 2020 at 07:06:54AM -0700, Paul E. McKenney wrote: > The current state in the C++ committee is that marking variables > carrying dependencies is the way forward. This is of course not what > the Linux kernel community does, but it should not be hard to have a > -fall-variables-dependent or some such that causes all variables to be > treated as if they were marked. Though I was hoping for only pointers. > Are they -sure- that they -absolutely- need to carry dependencies > through integers??? What's 'need'? :-) I'm thinking __ktime_get_fast_ns() is better off with a dependent load than it is with an extra smp_rmb(). Yes we can stick an smp_rmb() in there, but I don't like it. Like I wrote earlier, if I wanted a control dependency, I'd have written one. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel