From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 14FFF475 for ; Fri, 31 Jul 2015 18:59:42 +0000 (UTC) Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com [209.85.212.176]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 5CA7DE2 for ; Fri, 31 Jul 2015 18:59:41 +0000 (UTC) Received: by wibud3 with SMTP id ud3so68737112wib.1 for ; Fri, 31 Jul 2015 11:59:40 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150731182256.GA6508@kroah.com> References: <55BAE39F.9060705@oracle.com> <20150731165915.GA4995@roeck-us.net> <20150731170825.GA2721@kroah.com> <20150731171500.GC4995@roeck-us.net> <20150731181245.GA5969@kroah.com> <20150731181757.GA8747@codemonkey.org.uk> <20150731182256.GA6508@kroah.com> Date: Fri, 31 Jul 2015 11:59:39 -0700 Message-ID: From: Dan Williams To: Greg KH Content-Type: text/plain; charset=UTF-8 Cc: "ksummit-discuss@lists.linuxfoundation.org" , Sasha Levin Subject: Re: [Ksummit-discuss] Self nomination List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Jul 31, 2015 at 11:22 AM, Greg KH wrote: > On Fri, Jul 31, 2015 at 02:17:58PM -0400, Dave Jones wrote: >> On Fri, Jul 31, 2015 at 11:12:45AM -0700, Greg Kroah-Hartman wrote: >> > On Fri, Jul 31, 2015 at 12:51:53PM -0500, Bjorn Helgaas wrote: >> > > I prefer that a dmesg collected in the simplest possible way, with no >> > > special config or boot flags, be as useful as possible. So converting >> > > to dynamic debug requires much more thought about which messages >> > > should be always printed and which should become dynamic. >> > >> > Why would a debugging message ever not be dynamic? They are there for >> > you to use, and turn off when you are done. If you want a user to >> > report the output of them, then of course they should be dynamic so they >> > can just write a line to a debugfs file and then start seeing them >> >> This implies a user knows ahead of time what bugs they are going to hit, >> and which messages they need to enable. For hard-to-reproduce bugs, >> or bugs that exhibit non-obvious symptoms, this isn't workable. > > Fair enough, but wouldn't those messages be "errors"? > > Anyway, this is way off-topic from the original thread, it all comes > down to specifics of the message that is being written and the > surrounding issues of why it would be written. One more thought on this tangent... I've had a task stuck at the bottom of my backlog to look at extending dynamic_debug call sites to optionally be tracepoints so that you could feasibly have debug on all the time with less run time impact.