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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 58492C388F2 for ; Fri, 6 Nov 2020 17:02:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0581020720 for ; Fri, 6 Nov 2020 17:02:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604682152; bh=tOrhjB8801E1p+btlLJs95tpLOMvubFShNAI+eOrvNk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=1kVhDuv2f/SI2Hh/stBQsKagUR3RPCdrnjzFeNxVXZPEKomFQlyfu6Lr7Rm0oKJRi ZkxlkBMCEpvz5yhYdlo5+yG9s+EcqTyTrHtb/BjlkLHs4aZcLKkA2vqxvDuXHbnTVi fCS1IjL6MLI7sBx2/0+QVgEjrDbhoigkeGGQS3s8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727505AbgKFRC1 (ORCPT ); Fri, 6 Nov 2020 12:02:27 -0500 Received: from mail-lf1-f68.google.com ([209.85.167.68]:45203 "EHLO mail-lf1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726034AbgKFRC1 (ORCPT ); Fri, 6 Nov 2020 12:02:27 -0500 Received: by mail-lf1-f68.google.com with SMTP id z21so1595417lfe.12; Fri, 06 Nov 2020 09:02:25 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=IxgRn+NDQHTCeHwfBgvEL75Ff6LWDGq3sU/W0ROdACs=; b=IAJ8iU1BvxrdM2I3e2LNcRjjFUrkrBxAwYcNiFTuBg/CYbdJfpufGOYzvgoXAaWD9z Dc6SI7wOPMOq7BoOZkBCxoysFFkdlXy+0Ab7Gr+w/sR2E2yM7ec8AyrcnGl9AEhg3MQ/ 05asFOY06KdF+NMAIGP5V0UJnKLOcLxXucJ3x2ao5EhYUbxEQk+84UhXUtaui9jzPDBx GEiZ4vmlmzExey3qgTXdUodCDUaMNR2LihtppR0gsOkyjL+EOwyPBhMNrj5gEJi795MQ ihLB42WEWaNgNXNpdMweqqR/o8LWTtZOFqWbznr2qRcGyoAFTd8V1GakpWOusG7UZzRz RTzw== X-Gm-Message-State: AOAM530aI9QXCkcga9Kg0kz8kY0EsPg9hhVk2aQjxUPFJLAjNrJ+JP8W OTra2+jfbXlSHJD3+iTpp5IRQOMjttOuqA== X-Google-Smtp-Source: ABdhPJw79cVvhd1vcIuu4XPui96mAP4xDKV9ArN/Fggzk4GDVD5ecQaYCGh110VzE2qKOVR/aU9B5Q== X-Received: by 2002:a05:6512:104e:: with SMTP id c14mr1305423lfb.345.1604682144693; Fri, 06 Nov 2020 09:02:24 -0800 (PST) Received: from xi.terra (c-beaee455.07-184-6d6c6d4.bbcust.telenor.se. [85.228.174.190]) by smtp.gmail.com with ESMTPSA id r23sm225149lfe.228.2020.11.06.09.02.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2020 09:02:23 -0800 (PST) Received: from johan by xi.terra with local (Exim 4.93.0.4) (envelope-from ) id 1kb587-0000G4-23; Fri, 06 Nov 2020 18:02:27 +0100 Date: Fri, 6 Nov 2020 18:02:27 +0100 From: Johan Hovold To: Steven Rostedt Cc: Johan Hovold , Jessica Yu , linux-kernel@vger.kernel.org, Linus Torvalds , Rob Herring , Frank Rowand , Greg Kroah-Hartman , Nick Desaulniers , Arnd Bergmann , Geert Uytterhoeven , Dmitry Torokhov , David Miller , Jakub Jelinek , Peter Zijlstra , Thomas Gleixner , Daniel Kurtz , linux-arch@vger.kernel.org, linux-m68k@lists.linux-m68k.org Subject: Re: [PATCH 0/8] linker-section array fix and clean ups Message-ID: <20201106170227.GE4085@localhost> References: <20201103175711.10731-1-johan@kernel.org> <20201106160344.GA12184@linux-8ccs.fritz.box> <20201106164537.GD4085@localhost> <20201106115523.41f7e2ed@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106115523.41f7e2ed@gandalf.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, Nov 06, 2020 at 11:55:23AM -0500, Steven Rostedt wrote: > On Fri, 6 Nov 2020 17:45:37 +0100 > Johan Hovold wrote: > > > It's simply specifying alignment when declaring the variable that > > prevents this optimisation. The relevant code is in the function > > align_variable() in [1] where DATA_ALIGNMENT() is never called in case > > an alignment has been specified (!DECL_USER_ALIGN(decl)). > > > > There's no mention in the documentation of this that I'm aware of, but > > this is the way the aligned attribute has worked since its introduction > > judging from the commit history. > > > > As mentioned above, we've been relying on this for kernel parameters and > > other structures since 2003-2004 so if it ever were to change we'd find > > out soon enough. > > > > It's about to be used for scheduler classes as well. [2] > > Is this something that gcc folks are aware of? Yes, we appear to be relying > on undocumented implementations, but that hasn't caused gcc to break the > kernel in the past. The scheduler change was suggested by Jakub so at least some of them are. Johan