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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 B7592C04EB8 for ; Thu, 6 Dec 2018 11:52:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83F52208E7 for ; Thu, 6 Dec 2018 11:52:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 83F52208E7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=daenzer.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729498AbeLFLwn (ORCPT ); Thu, 6 Dec 2018 06:52:43 -0500 Received: from mail.netline.ch ([148.251.143.178]:58821 "EHLO netline-mail3.netline.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727832AbeLFLwm (ORCPT ); Thu, 6 Dec 2018 06:52:42 -0500 Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id 5A2192A604D; Thu, 6 Dec 2018 12:52:39 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at netline-mail3.netline.ch Received: from netline-mail3.netline.ch ([127.0.0.1]) by localhost (netline-mail3.netline.ch [127.0.0.1]) (amavisd-new, port 10024) with LMTP id flDF4AXnm3VD; Thu, 6 Dec 2018 12:52:34 +0100 (CET) Received: from thor (39.1.199.178.dynamic.wline.res.cust.swisscom.ch [178.199.1.39]) by netline-mail3.netline.ch (Postfix) with ESMTPSA id 05D502A604B; Thu, 6 Dec 2018 12:52:33 +0100 (CET) Received: from localhost ([::1]) by thor with esmtp (Exim 4.91) (envelope-from ) id 1gUsCn-0005i3-NV; Thu, 06 Dec 2018 12:52:33 +0100 Subject: Re: [PATCH 1/2] drm: Only #define DEBUG if CONFIG_DYNAMIC_DEBUG is disabled To: Joe Perches , "Zhang, Jerry(Junwei)" , Christian Koenig , Huang Rui , Maarten Lankhorst , Maxime Ripard , Sean Paul , David Airlie , Chris Wilson Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20181205165621.5805-1-michel@daenzer.net> <10fca21a-5d7c-fe9e-07f0-6200e9de538e@amd.com> <1586a49594d30b4bf4d88eba0d258e21efd26da2.camel@perches.com> <276fbf7f-d33f-83a5-cb88-bd4051dc03ba@daenzer.net> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Openpgp: preference=signencrypt Autocrypt: addr=michel@daenzer.net; prefer-encrypt=mutual; keydata= mQGiBDsehS8RBACbsIQEX31aYSIuEKxEnEX82ezMR8z3LG8ktv1KjyNErUX9Pt7AUC7W3W0b LUhu8Le8S2va6hi7GfSAifl0ih3k6Bv1Itzgnd+7ZmSrvCN8yGJaHNQfAevAuEboIb+MaVHo 9EMJj4ikOcRZCmQWw7evu/D9uQdtkCnRY9iJiAGxbwCguBHtpoGMxDOINCr5UU6qt+m4O+UD /355ohBBzzyh49lTj0kTFKr0Ozd20G2FbcqHgfFL1dc1MPyigej2gLga2osu2QY0ObvAGkOu WBi3LTY8Zs8uqFGDC4ZAwMPoFy3yzu3ne6T7d/68rJil0QcdQjzzHi6ekqHuhst4a+/+D23h Za8MJBEcdOhRhsaDVGAJSFEQB1qLBACOs0xN+XblejO35gsDSVVk8s+FUUw3TSWJBfZa3Imp V2U2tBO4qck+wqbHNfdnU/crrsHahjzBjvk8Up7VoY8oT+z03sal2vXEonS279xN2B92Tttr AgwosujguFO/7tvzymWC76rDEwue8TsADE11ErjwaBTs8ZXfnN/uAANgPLQjTWljaGVsIERh ZW56ZXIgPG1pY2hlbEBkYWVuemVyLm5ldD6IXgQTEQIAHgUCQFXxJgIbAwYLCQgHAwIDFQID AxYCAQIeAQIXgAAKCRBaga+OatuyAIrPAJ9ykonXI3oQcX83N2qzCEStLNW47gCeLWm/QiPY jqtGUnnSbyuTQfIySkK5AQ0EOx6FRRAEAJZkcvklPwJCgNiw37p0GShKmFGGqf/a3xZZEpjI qNxzshFRFneZze4f5LhzbX1/vIm5+ZXsEWympJfZzyCmYPw86QcFxyZflkAxHx9LeD+89Elx bw6wT0CcLvSv8ROfU1m8YhGbV6g2zWyLD0/naQGVb8e4FhVKGNY2EEbHgFBrAAMGA/0VktFO CxFBdzLQ17RCTwCJ3xpyP4qsLJH0yCoA26rH2zE2RzByhrTFTYZzbFEid3ddGiHOBEL+bO+2 GNtfiYKmbTkj1tMZJ8L6huKONaVrASFzLvZa2dlc2zja9ZSksKmge5BOTKWgbyepEc5qxSju YsYrX5xfLgTZC5abhhztpYhGBBgRAgAGBQI7HoVFAAoJEFqBr45q27IAlscAn2Ufk2d6/3p4 Cuyz/NX7KpL2dQ8WAJ9UD5JEakhfofed8PSqOM7jOO3LCA== Message-ID: Date: Thu, 6 Dec 2018 12:52:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-12-06 12:41 p.m., Joe Perches wrote: > On Thu, 2018-12-06 at 10:23 +0100, Michel Dänzer wrote: >> On 2018-12-06 3:51 a.m., Joe Perches wrote: >>> On Thu, 2018-12-06 at 10:40 +0800, Zhang, Jerry(Junwei) wrote: >>>> On 12/6/18 12:56 AM, Michel Dänzer wrote: >>>>> From: Michel Dänzer >>>>> >>>>> The following cases are possible for pr_debug(): >>>>> >>>>> 1. CONFIG_DYNAMIC_DEBUG disabled >>>>> a) DEBUG not defined: pr_debug() translates to no_printk(...), i.e. >>>>> it never generates any output. >>>>> b) DEBUG defined: pr_debug() translates to printk(KERN_DEBUG ...), >>>>> i.e. it generates output which doesn't appear in dmesg by default, >>>>> can be enabled dynamically. >>>>> >>>>> 2. CONFIG_DYNAMIC_DEBUG enabled: pr_debug() translates to >>>>> dynamic_pr_debug() >>>>> a) DEBUG not defined: dynamic_pr_debug() generates no output by >>>>> default, can be enabled dynamically. >>>>> b) DEBUG defined: dynamic_pr_debug() generates output by default, >>>>> can be disabled dynamically. >>>>> >>>>> The intention for drm_debug_printer() is to generate output which >>>>> doesn't appear in dmesg by default, but can be enabled dynamically, i.e. >>>>> cases 1b) and 2a). However, defining DEBUG unconditionally gave us 2b) >>>>> instead of 2a) with CONFIG_DYNAMIC_DEBUG enabled. >>>>> >>>>> Fixes: 79a5ad2fdb3c ("drm: Enable pr_debug() for drm_printer") >>> >>> I very much doubt this is a fix. >>> >>> Did you read the commit log for this commit? >>> >>> It says "make sure it will always produce output" >> >> I thought the commit log covered this, suggestions for improvement welcome. >> >> Chris' change addressed case 1a), but also took us from 2a) to 2b). But >> we want 2a) > >> I suspect Chris missed that pr_debug()'s output is visible by default if >> CONFIG_DYNAMIC_DEBUG and DEBUG are both defined. > > I believe you and Chris have different goals and that your > point of 2b is > misguided. > > I think the language used in the Chris' commit log is > plain ans obvious. 'always produce output'. That was probably meant as "make sure there always can be output", which isn't the case with 1a (no_printk suppresses the output at compile time, the strings might not even exist in the binaries). In contrast to the 2b case, the pr_debug output isn't visible by default with 1b, so the latter doesn't fit "always produce output" either. But Chris' initial follow-up in this thread seems to confirm my assumption that his change was about 1a/b. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer