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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 8DD28C49ED6 for ; Wed, 11 Sep 2019 18:28:08 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 6CFEA2085B for ; Wed, 11 Sep 2019 18:28:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CFEA2085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55144 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i87Lb-000869-M5 for qemu-devel@archiver.kernel.org; Wed, 11 Sep 2019 14:28:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41042) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i87Kn-0007ag-4d for qemu-devel@nongnu.org; Wed, 11 Sep 2019 14:27:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i87Kl-0006uM-GQ for qemu-devel@nongnu.org; Wed, 11 Sep 2019 14:27:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42440) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i87Kl-0006tO-7a for qemu-devel@nongnu.org; Wed, 11 Sep 2019 14:27:15 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 49AED300BEAC for ; Wed, 11 Sep 2019 18:27:14 +0000 (UTC) Received: from work-vm (ovpn-117-243.ams2.redhat.com [10.36.117.243]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 72EDC60C83; Wed, 11 Sep 2019 18:27:11 +0000 (UTC) Date: Wed, 11 Sep 2019 19:27:09 +0100 From: "Dr. David Alan Gilbert" To: Eric Blake Message-ID: <20190911182709.GM2894@work-vm> References: <20190911164202.31136-1-dgilbert@redhat.com> <20190911164202.31136-2-dgilbert@redhat.com> <1a03f787-5cf8-6b8e-7489-3f90c3311032@redhat.com> <4c73915d-c4c8-0829-855b-ab5775d7e6fe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4c73915d-c4c8-0829-855b-ab5775d7e6fe@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Wed, 11 Sep 2019 18:27:14 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 1/3] rcu: Add automatically released rcu_read_lock variant X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, berrange@redhat.com, qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Eric Blake (eblake@redhat.com) wrote: > On 9/11/19 12:40 PM, Eric Blake wrote: > > >> + > >> +#define RCU_READ_LOCK_AUTO g_auto(rcu_read_auto_t) \ > >> + _rcu_read_auto = 'x'; \ > > > > I'm a bit lost at where _rcu_read_auto is declared. (I could understand > > if an earlier macro had created that typedef via concatenating _ with > > rcu_read_auto_t, but making the preprocessor drop _t is not possible. Is > > this a typo, and if so, why did the compiler not complain?) > > Okay, I read it wrong. This rendering would be easier for me to > understand (you are declaring a dummy variable right here): > > #define RCU_READ_LOCK_AUTO \ > g_auto(rcu_read_auto_t) _rcu_read_auto = 'x'; \ > ... > > In other words, I'm not used to expecting a split between type and > variable name across two lines, especially when the type is itself a > macro call, and where my first reading didn't spot that > (rcu_read_auto_t) was not the name of the argument to a mixed-case macro > RCU_READ_LOACK_AUTO_g_auto, rather than g_auto(...) being the start of > the parameter-less macro RCU_READ_LOCK_AUTO definition. Yep, that's simplified after the rework Dan suggested. Dave > -- > Eric Blake, Principal Software Engineer > Red Hat, Inc. +1-919-301-3226 > Virtualization: qemu.org | libvirt.org > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK