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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 626EEC04AB5 for ; Mon, 3 Jun 2019 18:43:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 36E3A270A5 for ; Mon, 3 Jun 2019 18:43:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=synopsys.com header.i=@synopsys.com header.b="cPJC4bgb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726683AbfFCSna (ORCPT ); Mon, 3 Jun 2019 14:43:30 -0400 Received: from smtprelay-out1.synopsys.com ([198.182.47.102]:42344 "EHLO smtprelay-out1.synopsys.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726055AbfFCSn3 (ORCPT ); Mon, 3 Jun 2019 14:43:29 -0400 Received: from mailhost.synopsys.com (dc8-mailhost1.synopsys.com [10.13.135.209]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by smtprelay-out1.synopsys.com (Postfix) with ESMTPS id CCF8FC1E03; Mon, 3 Jun 2019 18:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=synopsys.com; s=mail; t=1559587419; bh=CHQdvmHpZ+nNkXgwTaRppfMOKNBm5bThrSa4Dlvw3O4=; h=Subject:To:CC:References:From:Date:In-Reply-To:From; b=cPJC4bgbctAhHRufhBWEQXyiDzTNCOD1l1jtppO66BWIaTQN0sf6BCC3kZW8KN1O0 0P4YknM0CEwgY371CHazcYw76x7cGgQ9SxsHRdgM1c2byC1lJsoepTcvO/SkDWtJQ3 8ifCYP1JHYcimcmwXPn0JJq9wo9rSqrsMg7/ncFdRP+Huqmk6gkW41O6u19J8YLjjj UYBESk46oqCN40ZL62jb92maAyL1hiYwuZmSB4GL8NlH+FBVfAWqV6W6YZJGVh9zuk rCI6peCKbt7PHHPfGJIBlq9bZRMRO43koCpnKtkhbqSv3eK9CkAKq8npgP9BNA4CZK B38HfFTgkNE5Q== Received: from US01WXQAHTC1.internal.synopsys.com (us01wxqahtc1.internal.synopsys.com [10.12.238.230]) (using TLSv1.2 with cipher AES128-SHA256 (128/128 bits)) (No client certificate requested) by mailhost.synopsys.com (Postfix) with ESMTPS id 8E8FEA005D; Mon, 3 Jun 2019 18:43:28 +0000 (UTC) Received: from IN01WEHTCB.internal.synopsys.com (10.144.199.106) by US01WXQAHTC1.internal.synopsys.com (10.12.238.230) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 3 Jun 2019 11:43:28 -0700 Received: from IN01WEHTCA.internal.synopsys.com (10.144.199.103) by IN01WEHTCB.internal.synopsys.com (10.144.199.105) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 4 Jun 2019 00:13:25 +0530 Received: from [10.10.161.35] (10.10.161.35) by IN01WEHTCA.internal.synopsys.com (10.144.199.243) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 4 Jun 2019 00:13:37 +0530 Subject: Re: single copy atomicity for double load/stores on 32-bit systems To: Peter Zijlstra CC: Will Deacon , "Paul E. McKenney" , arcml , lkml , "linux-arch@vger.kernel.org" Newsgroups: gmane.linux.kernel,gmane.linux.kernel.arc,gmane.linux.kernel.cross-arch References: <2fd3a455-6267-5d21-c530-41964a4f6ce9@synopsys.com> <20190531082112.GH2623@hirez.programming.kicks-ass.net> From: Vineet Gupta Openpgp: preference=signencrypt Autocrypt: addr=vgupta@synopsys.com; keydata= mQINBFEffBMBEADIXSn0fEQcM8GPYFZyvBrY8456hGplRnLLFimPi/BBGFA24IR+B/Vh/EFk B5LAyKuPEEbR3WSVB1x7TovwEErPWKmhHFbyugdCKDv7qWVj7pOB+vqycTG3i16eixB69row lDkZ2RQyy1i/wOtHt8Kr69V9aMOIVIlBNjx5vNOjxfOLux3C0SRl1veA8sdkoSACY3McOqJ8 zR8q1mZDRHCfz+aNxgmVIVFN2JY29zBNOeCzNL1b6ndjU73whH/1hd9YMx2Sp149T8MBpkuQ cFYUPYm8Mn0dQ5PHAide+D3iKCHMupX0ux1Y6g7Ym9jhVtxq3OdUI5I5vsED7NgV9c8++baM 7j7ext5v0l8UeulHfj4LglTaJIvwbUrCGgtyS9haKlUHbmey/af1j0sTrGxZs1ky1cTX7yeF nSYs12GRiVZkh/Pf3nRLkjV+kH++ZtR1GZLqwamiYZhAHjo1Vzyl50JT9EuX07/XTyq/Bx6E dcJWr79ZphJ+mR2HrMdvZo3VSpXEgjROpYlD4GKUApFxW6RrZkvMzuR2bqi48FThXKhFXJBd JiTfiO8tpXaHg/yh/V9vNQqdu7KmZIuZ0EdeZHoXe+8lxoNyQPcPSj7LcmE6gONJR8ZqAzyk F5voeRIy005ZmJJ3VOH3Gw6Gz49LVy7Kz72yo1IPHZJNpSV5xwARAQABtCpWaW5lZXQgR3Vw dGEgKGFsaWFzKSA8dmd1cHRhQHN5bm9wc3lzLmNvbT6JAj4EEwECACgCGwMGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheABQJbBYpwBQkLx0HcAAoJEGnX8d3iisJeChAQAMR2UVbJyydOv3aV jmqP47gVFq4Qml1weP5z6czl1I8n37bIhdW0/lV2Zll+yU1YGpMgdDTHiDqnGWi4pJeu4+c5 xsI/VqkH6WWXpfruhDsbJ3IJQ46//jb79ogjm6VVeGlOOYxx/G/RUUXZ12+CMPQo7Bv+Jb+t NJnYXYMND2Dlr2TiRahFeeQo8uFbeEdJGDsSIbkOV0jzrYUAPeBwdN8N0eOB19KUgPqPAC4W HCg2LJ/o6/BImN7bhEFDFu7gTT0nqFVZNXlOw4UcGGpM3dq/qu8ZgRE0turY9SsjKsJYKvg4 djAaOh7H9NJK72JOjUhXY/sMBwW5vnNwFyXCB5t4ZcNxStoxrMtyf35synJVinFy6wCzH3eJ XYNfFsv4gjF3l9VYmGEJeI8JG/ljYQVjsQxcrU1lf8lfARuNkleUL8Y3rtxn6eZVtAlJE8q2 hBgu/RUj79BKnWEPFmxfKsaj8of+5wubTkP0I5tXh0akKZlVwQ3lbDdHxznejcVCwyjXBSny d0+qKIXX1eMh0/5sDYM06/B34rQyq9HZVVPRHdvsfwCU0s3G+5Fai02mK68okr8TECOzqZtG cuQmkAeegdY70Bpzfbwxo45WWQq8dSRURA7KDeY5LutMphQPIP2syqgIaiEatHgwetyVCOt6 tf3ClCidHNaGky9KcNSQ Message-ID: <77b30ed2-3211-222b-1342-051a6cde4f77@synopsys.com> Date: Mon, 3 Jun 2019 11:43:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190531082112.GH2623@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.10.161.35] Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/31/19 1:21 AM, Peter Zijlstra wrote: > And I'll stand by my earlier conviction that any architecture that has a > native u64 (be it a 64bit arch or a 32bit with double-width > instructions) but has an ABI that allows u32 alignment on them is daft. Why ? For 64-bit data on 32-bit systems, hardware doesn't claim to provide any single-copy atomicity for such data and software doesn't expect either.