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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 906EAC33CB2 for ; Fri, 31 Jan 2020 10:20:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5CEBE20705 for ; Fri, 31 Jan 2020 10:20:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hdbfVVhb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728333AbgAaKUi (ORCPT ); Fri, 31 Jan 2020 05:20:38 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:47652 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728289AbgAaKUi (ORCPT ); Fri, 31 Jan 2020 05:20:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580466037; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9Rvip+9gEMjJ6H84OHoQUknXeHPGXzmy72y0DuVzxqY=; b=hdbfVVhbnrTdV/DBYBjxYhjjKXuzhKygdYWxtIUNy3nk4nagKbDH/DARq/r0rJGU6xNcC/ zUNltzFBdClP0pcXbVnY9/mRju29LmwjXY9MyUiZOb8yteXrg4dymhN9ypx+QiUSimWnoc T357e2fcnsjOQH2+55db1i1Nsd5srag= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-121-degvaMcmNIy88Nk77AIFyA-1; Fri, 31 Jan 2020 05:20:28 -0500 X-MC-Unique: degvaMcmNIy88Nk77AIFyA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A1549107ACC4; Fri, 31 Jan 2020 10:20:25 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-218.rdu2.redhat.com [10.10.120.218]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9E46F5DA75; Fri, 31 Jan 2020 10:20:22 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20200123153341.19947-1-will@kernel.org> To: Linus Torvalds Cc: dhowells@redhat.com, Will Deacon , Alexey Dobriyan , Linux Kernel Mailing List , linux-arch , Android Kernel Team , Michael Ellerman , Peter Zijlstra , Segher Boessenkool , Christian Borntraeger , Luc Van Oostenryck , Arnd Bergmann , Peter Oberparleiter , Masahiro Yamada , Nick Desaulniers Subject: Re: [PATCH v2 00/10] Rework READ_ONCE() to improve codegen MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <7435.1580466021.1@warthog.procyon.org.uk> Date: Fri, 31 Jan 2020 10:20:21 +0000 Message-ID: <7436.1580466021@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Of course, if you're feeling adventurous and willing to at least entertain the mere speculation of switching the kernel source to C++, we could then use inline template functions: template static inline T __READ_ONCE(T &var) { T val = *(const volatile T *)&var; return val; } template static inline T READ_ONCE(T &var) { T val; compiletime_assert_rwonce_type(var); val = __READ_ONCE(var); smp_read_barrier_depends(); return val; } Of course, that would mean using C++... David