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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 BD11AC433DF for ; Fri, 21 Aug 2020 00:36:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A491020738 for ; Fri, 21 Aug 2020 00:36:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726965AbgHUAgG (ORCPT ); Thu, 20 Aug 2020 20:36:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:34290 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726840AbgHUAgF (ORCPT ); Thu, 20 Aug 2020 20:36:05 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6E07820720; Fri, 21 Aug 2020 00:36:03 +0000 (UTC) Date: Thu, 20 Aug 2020 20:36:01 -0400 From: Steven Rostedt To: Nicolas Boichat Cc: Mauro Carvalho Chehab , Greg Kroah-Hartman , Andy Shevchenko , Sakari Ailus , devel@driverdev.osuosl.org, lkml , Linux Media Mailing List , Peter Zijlstra , Thomas Gleixner , Josh Poimboeuf Subject: Re: [PATCH v4 3/3] media: atomisp: Only use trace_printk if allowed Message-ID: <20200820203601.4f70bf98@oasis.local.home> In-Reply-To: References: <20200820170951.v4.1.Ia54fe801f246a0b0aee36fb1f3bfb0922a8842b0@changeid> <20200820170951.v4.3.I066d89f39023956c47fb0a42edf196b3950ffbf7@changeid> <20200820102347.15d2f610@oasis.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 21 Aug 2020 08:13:00 +0800 Nicolas Boichat wrote: > On Thu, Aug 20, 2020 at 10:23 PM Steven Rostedt wrote: > > > > On Thu, 20 Aug 2020 17:14:12 +0800 > > Nicolas Boichat wrote: > > > > > Technically, we could only initialize the trace_printk buffers > > > when the print env is switched, to avoid the build error and > > > unconditional boot-time warning, but I assume this printing > > > framework will eventually get removed when the driver moves out > > > of staging? > > > > Perhaps this should be converting into a trace event. Look at what bpf > > did for their bpf_trace_printk(). > > > > The more I think about it, the less I like this series. > > To make it clear, the primary goal of this series is to get rid of > trace_printk sprinkled in the kernel by making sure some randconfig > builds fail. Since my v2, there already has been one more added (the > one that this patch removes), so I'd like to land 2/3 ASAP to prevent > even more from being added. > > Looking at your reply on 1/3, I think we are aligned on that goal? Is > there some other approach you'd recommend? > > Now, I'm not pretending my fixes are the best possible ones, but I > would much rather have the burden of converting to trace events on the > respective driver maintainers. (btw is there a short > documentation/tutorial that I could link to in these patches, to help > developers understand what is the recommended way now?) > I like the goal, but I guess I never articulated the problem I have with the methodology. trace_printk() is meant to be a debugging tool. Something that people can and do sprinkle all over the kernel to help them find a bug in areas that are called quite often (where printk() is way too slow). The last thing I want them to deal with is adding a trace_printk() with their distro's config (or a config from someone that triggered the bug) only to have the build to fail, because they also need to add a config value. I add to the Cc a few developers I know that use trace_printk() in this fashion. I'd like to hear their view on having to add a config option to make trace_printk work before they test a config that is sent to them. -- Steve