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=-7.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 00216C433DF for ; Fri, 3 Jul 2020 14:53:03 +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 C2772206A1 for ; Fri, 3 Jul 2020 14:53:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="0hpxtQGW"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="P08qXOSK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C2772206A1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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:Reply-To:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jjj9deyStOUZoCN4ijsa4At7Kpli9tVvBFYASqvSd4M=; b=0hpxtQGW5R3RoKFxVIlezDT2Tr caYuW7qGpDPRQPQyuZTKQy4S/PwmUthGlKKF027CpRXzdXdRGBSotzVl25reH7JYPV2v3Fiws1DVh zXXORW3bzTIAPJEjKL9MzPB6QwCDyEPeZQ6G21gzNoNYvjQ6T1pbIMwciGGCCp/HJJlrWwQAMSK1c kvOa3JbMHkh99rQIMsX8KjSzQiVpSaAtbaslxPypYhDT4uYABqxVCeunyAC+OQpMA/yzZrxgqI11n uQAwEUNbYO66/ff32nmgklJ/sQjb+CS8Fst50ca0XhMJV/1ZBTZLCHVTwj8aWcrL1phpDDkaqHsi0 QjiUM9sQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jrN2h-0003qq-12; Fri, 03 Jul 2020 14:51:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jrN2d-0003ov-VV for linux-arm-kernel@lists.infradead.org; Fri, 03 Jul 2020 14:51:52 +0000 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 61D192088E; Fri, 3 Jul 2020 14:51:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593787911; bh=OfQ9QrrhTEkwVc9D/6kQ4OLMbBVifUwGjpIqyu/to+g=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=P08qXOSK/SsmY8VAxSWxJZlh9y2mElMtAZzYp/JpETdbeuKyxfeNiEOPVeAjMtgmm cVQ6zWd/th8wPaVLaFElx/6ZkEKB/7VSwS0fonaGWl2nOftDG+g5Bf9ZqxlWOJSJrJ eDszUhoHxsOqHSNzzZyn6clVtx/aI8MGpxWzyq84= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 4C40135206C0; Fri, 3 Jul 2020 07:51:51 -0700 (PDT) Date: Fri, 3 Jul 2020 07:51:51 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200703145151.GG9247@paulmck-ThinkPad-P72> References: <20200630203016.GI9247@paulmck-ThinkPad-P72> <20200701114027.GO4800@hirez.programming.kicks-ass.net> <20200701140654.GL9247@paulmck-ThinkPad-P72> <20200701150512.GH4817@hirez.programming.kicks-ass.net> <20200701160338.GN9247@paulmck-ThinkPad-P72> <20200702082040.GB4781@hirez.programming.kicks-ass.net> <20200702175948.GV9247@paulmck-ThinkPad-P72> <20200703131330.GX4800@hirez.programming.kicks-ass.net> <20200703132523.GM117543@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200703132523.GM117543@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200703_105152_095390_35002E97 X-CRM114-Status: GOOD ( 16.26 ) 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: , Reply-To: paulmck@kernel.org 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 Fri, Jul 03, 2020 at 03:25:23PM +0200, Peter Zijlstra wrote: > On Fri, Jul 03, 2020 at 03:13:30PM +0200, Peter Zijlstra wrote: > > > The prototype for GCC is here: https://github.com/AKG001/gcc/ > > > > Thanks! Those test cases are somewhat over qualified though: > > > > static volatile _Atomic (TYPE) * _Dependent_ptr a; \ > > One question though; since its a qualifier, and we've recently spend a > whole lot of effort to strip qualifiers in say READ_ONCE(), how does, > and how do we want, this qualifier to behave. Dereferencing a _Dependent_ptr pointer gives you something that is not _Dependent_ptr, unless the declaration was like this: _Dependent_ptr _Atomic (TYPE) * _Dependent_ptr a; And if I recall correctly, the current state is that assigning a _Dependent_ptr variable to a non-_Dependent_ptr variable strips this marking (though the thought was to be able to ask for a warning). So, yes, it would be nice to be able to explicitly strip the _Dependent_ptr, perhaps the kill_dependency() macro, which is already in the C standard. > C++ has very convenient means of manipulating qualifiers, so it's not > much of a problem there, but for C it is, as we've found, really quite > cumbersome. Even with _Generic() we can't manipulate individual > qualifiers afaict. Fair point, and in C++ this is a templated class, at least in the same sense that std::atomic<> is a templated class. But in this case, would kill_dependency do what you want? Thanx, Paul _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel