Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758136Ab2FZAXO (ORCPT ); Mon, 25 Jun 2012 20:23:14 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:59231 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757167Ab2FZAXM (ORCPT ); Mon, 25 Jun 2012 20:23:12 -0400 Date: Mon, 25 Jun 2012 17:23:07 -0700 From: Greg Kroah-Hartman To: Linus Torvalds Cc: Andrew Morton , Steven Rostedt , LKML , Ingo Molnar , "kay.sievers" , Wu Fengguang , Joe Perches , "Paul E. McKenney" Subject: Re: [PATCH v3] printk: Have printk() never buffer its data Message-ID: <20120626002307.GA4389@kroah.com> References: <1340651142.7037.2.camel@gandalf.stny.rr.com> <20120625150722.8cd4f45d.akpm@linux-foundation.org> <20120625235531.GB3652@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2146 Lines: 50 On Mon, Jun 25, 2012 at 05:01:11PM -0700, Linus Torvalds wrote: > On Mon, Jun 25, 2012 at 4:55 PM, Greg Kroah-Hartman > wrote: > > > > Stephen and Ingo, I understand that your tests now would require > > multiple printk() lines, but this affects what, 10 boxes in the world > > that run these tests (I'm not trying to be mean, just understand the > > issues). ?The fixes that now are in place fix problems for many more > > systems, and provide the infrastructure for proper logging that people > > have been screaming at us for over 10 years to accomplish. > > I disagree violently. > > I think we absolutely should apply Steven's patch. > > Why? Because the buffering does not help *anything*, and it's > surprising, and it breaks one of our main debugging tools. There's no > upside to it. Ok, but I thought you wanted the "properly handle continuations" that we now have in the kernel. I must be mistaken. > The fact that we found *one* case where it broke within days of it > being introduced is not the issue. Fixing that one case is irrelevant. > It's the unknown number of other cases that did similar thngs that > matter. > > If there are other places that print out partial lines, they may have > this problem too. Don't buffer. > > And if there are *not* other places that print out partial lines, then > buffering doesn't help. Don't buffer. > > Notice? Buffering partial lines is never *ever* the right thing to do > for something like printk. > > If you want to merge the partial lines, do it at the *logging* stage, > not at the printout stage. Nobody cares if you buffer the stuff that > actually makes it to "dmesg". But buffering the stuff before it makes > it to the screen is just wrong. Ok, Kay, does Stephen's patch work for you as well? I'll go boot a box with it and look at the output, but that will take 30 minutes or so... greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/