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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 61C66C433EF for ; Wed, 19 Jan 2022 08:10:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Ufl1DsEqrtCLx9QTjVPYawvJgyGwlZ2HzBgOxwBh3ZA=; b=NdHiuH2MHAdLgN WXvr8CTqX8dib+qmAd0jg7DdzuYjxPzySSXlxRL/BP30Isub3hj5MEDohek7vX8/unoMDjkr67SQf P9FyM64vuZRG3+2EJZtzigQz/yVgoxe4U15MZHGQTZnXVNPpe5BLB/1EQzHz1cFYQHXe9Z+dBQBYX GkYdKVjequ1Wm7NkIYrwDoVTT7cjZn7d2EOx8cq6smYeZ7Xae7uhWrbVyl3rjiDqXn4eCwlH4Iz2L kyCu/hPXWLlZx93Tj97gNYwuIUv38Ib4VA+6Tz4/k4vs5+KAbWjAmIRpenaG0MvY+VapISv5oPkDP jnj+M25rO0gFY40xL+xA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nA61x-004IAF-O0; Wed, 19 Jan 2022 08:09:21 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nA61t-004I8m-7l for linux-arm-kernel@lists.infradead.org; Wed, 19 Jan 2022 08:09:18 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1642579756; 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=q0Jq/iGEAUJBFkaTrvUcXumSON7O+wGuH4/+IOrgIh0=; b=DRRTP0hrHmq1GvQPymAF5D9VqgjLFTrRFMs7juHQlSATLKknMd5li6r/i1LaI6mMxbbpLO K3A8xXLcPifrxR9C+DOB2AgT8hOAthbw16pbYiPtMGse+6X9N1RK01bdWwP2h4GMdIsUhb iVqojqi0EAkoNLx1sJt3BdU0zXiAaeA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-395-TgfGWhqJOGu-EvyU0rV6uw-1; Wed, 19 Jan 2022 03:09:12 -0500 X-MC-Unique: TgfGWhqJOGu-EvyU0rV6uw-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 A8A651006AA4; Wed, 19 Jan 2022 08:09:09 +0000 (UTC) Received: from localhost (ovpn-12-206.pek2.redhat.com [10.72.12.206]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 06F94607CB; Wed, 19 Jan 2022 08:09:01 +0000 (UTC) Date: Wed, 19 Jan 2022 16:08:59 +0800 From: Baoquan He To: Jisheng Zhang Cc: Russell King , Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, hpa@zytor.com, Eric Biederman , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kexec@lists.infradead.org, Alexandre ghiti Subject: Re: [PATCH v2 0/5] kexec: use IS_ENABLED(CONFIG_KEXEC_CORE) instead of #ifdef Message-ID: <20220119080859.GB4977@MiWiFi-R3L-srv> References: <20211206160514.2000-1-jszhang@kernel.org> <20220116133847.GE2388@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220119_000917_388400_373BC2E7 X-CRM114-Status: GOOD ( 26.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 01/18/22 at 10:13pm, Jisheng Zhang wrote: > On Sun, Jan 16, 2022 at 09:38:47PM +0800, Baoquan He wrote: > > Hi Jisheng, > > Hi Baoquan, > > > > > On 12/07/21 at 12:05am, Jisheng Zhang wrote: > > > Replace the conditional compilation using "#ifdef CONFIG_KEXEC_CORE" > > > by a check for "IS_ENABLED(CONFIG_KEXEC_CORE)", to simplify the code > > > and increase compile coverage. > > > > I go through this patchset, You mention the benefits it brings are > > 1) simplity the code; > > 2) increase compile coverage; > > > > For benefit 1), it mainly removes the dummy function in x86, arm and > > arm64, right? > > Another benefit: remove those #ifdef #else #endif usage. Recently, I > fixed a bug due to lots of "#ifdefs": > http://lists.infradead.org/pipermail/linux-riscv/2021-December/010607.html Glad to know the fix. While, sometime the ifdeffery is necessary. I am sorry about the one in riscv and you have fixed, it's truly a bug . But, the increasing compile coverage at below you tried to make, it may cause issue. Please see below my comment. > > > > > For benefit 2), increasing compile coverage, could you tell more how it > > achieves and why it matters? What if people disables CONFIG_KEXEC_CORE in > > purpose? Please forgive my poor compiling knowledge. > > Just my humble opinion, let's compare the code:: > > #ifdef CONFIG_KEXEC_CORE > > code block A; > > #endif > > If KEXEC_CORE is disabled, code block A won't be compiled at all, the > preprocessor will remove code block A; > > If we convert the code to: > > if (IS_ENABLED(CONFIG_KEXEC_CORE)) { > code block A; > } > > Even if KEXEC_CORE is disabled, code block A is still compiled. This is what I am worried about. Before, if CONFIG_KEXEC_CORE is unset, those relevant codes are not compiled in. I can't see what benefit is brought in if compiled in the unneeded code block. Do I miss anything? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel