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=-6.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 A41B9C2D0A3 for ; Fri, 6 Nov 2020 05:12:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4CB6F2078B for ; Fri, 6 Nov 2020 05:12:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gH4mN2yO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726140AbgKFFMp (ORCPT ); Fri, 6 Nov 2020 00:12:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbgKFFMo (ORCPT ); Fri, 6 Nov 2020 00:12:44 -0500 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73C1AC0613CF; Thu, 5 Nov 2020 21:12:43 -0800 (PST) Received: by mail-pl1-x62c.google.com with SMTP id j5so123580plk.7; Thu, 05 Nov 2020 21:12:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=qaz5JfSXEexVzd3vu4/X1zvrfhtSmuN9aWiTUHv9SJA=; b=gH4mN2yOR56HxWAUwIJnrOftunZr9+x3k3rBsiRJpCEksBtaVdkAckIA/ShkL3YK2I mkGL3Hy4IUaQz762pvnkx4KwUGB3BGF80qajcWfFjd3npfm501lmjQmXotnZ6fWWFPTv HtGAsH4Nr6zqgcBut3cJLOkkA6HjcjzOeiBgQOQmGIkHpBIZk7SfvgFKzre4bD6er3ya gXaAFbMsf1CME3CF83weO8ROcpeFuEPeflYeITDaZa9G75buQ0cI5aO6IItXmjHRFbEM 99PGhazX1x6zc9vZ5TEqTrOmrufIVnDJhwjCUGQym7gCog8MXh3QtEriERKx5ZABf9rB HpBg== 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=qaz5JfSXEexVzd3vu4/X1zvrfhtSmuN9aWiTUHv9SJA=; b=E0+AataMUa682FCPcKRIc4KvhuaaCmYoq84qvddpsAneH0F7ANcc83+0z66qme/Nb0 5P+AW45235aYe5+xvp/0pj7x9VHBQR0ohmUYunXOKP45K5kE/znJ3rGuVbdTAEV9Sjdj 6Zl2VRteDgd7vk9oiqyM29mFNj9LpBnp/OEJ/AJsY4suAehQknJBzbndfNvpKbl3g7XI Ds6rHH7eILjQcfDbvUrMGUDC/h06piQzXkqOGLbTp33Beuz8hzzTjw477TvRbSmlVfIg Jdz6W3oU+F3AWXWjpDcfLLwIElfTxfkfVMTRRZMHi10e2N+L4dpunQZPoM6ohiQswYG+ 3SIg== X-Gm-Message-State: AOAM5300m2CpRdfY0z3urnwXhd+zDPol8hAA3jVt4gRa3zgBoCl1vHqm HqBG+zXV9VKPMKDW3z2Z8V0= X-Google-Smtp-Source: ABdhPJyn8OECd6Yk2g1TFuxtsKbYq4FLzAeVOngn/1xDW9/NSK6CjFcd/h0m9+vl0XlPDiPDXxLHrQ== X-Received: by 2002:a17:902:d698:b029:d6:b974:13c5 with SMTP id v24-20020a170902d698b02900d6b97413c5mr339670ply.13.1604639563004; Thu, 05 Nov 2020 21:12:43 -0800 (PST) Received: from localhost ([2409:10:2e40:5100:6e29:95ff:fe2d:8f34]) by smtp.gmail.com with ESMTPSA id j184sm320461pfg.207.2020.11.05.21.12.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2020 21:12:42 -0800 (PST) Date: Fri, 6 Nov 2020 14:12:40 +0900 From: Sergey Senozhatsky To: Lukas Bulwahn Cc: Petr Mladek , Sergey Senozhatsky , Steven Rostedt , John Ogness , Nathan Chancellor , Nick Desaulniers , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, kernel-janitors@vger.kernel.org, linux-safety@lists.elisa.tech Subject: Re: [PATCH] printk: remove unneeded dead-store assignment Message-ID: <20201106051240.GC4718@jagdpanzerIV.localdomain> References: <20201106034005.18822-1-lukas.bulwahn@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106034005.18822-1-lukas.bulwahn@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/11/06 04:40), Lukas Bulwahn wrote: > make clang-analyzer on x86_64 defconfig caught my attention with: > > kernel/printk/printk_ringbuffer.c:885:3: warning: > Value stored to 'desc' is never read [clang-analyzer-deadcode.DeadStores] > desc = to_desc(desc_ring, head_id); > ^ > > Commit b6cf8b3f3312 ("printk: add lockless ringbuffer") introduced > desc_reserve() with this unneeded dead-store assignment. > > As discussed with John Ogness privately, this is probably just some minor > left-over from previous iterations of the ringbuffer implementation. So, > simply remove this unneeded dead assignment to make clang-analyzer happy. > > As compilers will detect this unneeded assignment and optimize this anyway, > the resulting object code is identical before and after this change. > > No functional change. No change to object code. > > Signed-off-by: Lukas Bulwahn Reviewed-by: Sergey Senozhatsky -ss