From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754897AbaITQaG (ORCPT ); Sat, 20 Sep 2014 12:30:06 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.230]:31982 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752688AbaITQaE (ORCPT ); Sat, 20 Sep 2014 12:30:04 -0400 Date: Sat, 20 Sep 2014 12:30:01 -0400 From: Steven Rostedt To: Joe Perches Cc: Peter Zijlstra , Jan Kara , Markus Trippelsdorf , Geert Uytterhoeven , "linux-kernel@vger.kernel.org" , Andrew Morton Subject: Re: [PATCH] printk: git rid of [sched_delayed] message for printk_deferred Message-ID: <20140920123001.4ac60dba@gandalf.local.home> In-Reply-To: <1411229447.24444.53.camel@joe-AO725> References: <20140916203510.GF1205@quack.suse.cz> <20140916170709.73ef2993@gandalf.local.home> <20140916212250.GI1205@quack.suse.cz> <20140916173328.6306a5c2@gandalf.local.home> <20140917141816.GO2840@worktop.localdomain> <20140917102255.5cd03071@gandalf.local.home> <20140917223633.GE2848@worktop.localdomain> <20140917203135.6db2ee5e@gandalf.local.home> <20140918173414.GU2840@worktop.localdomain> <20140920051224.GA5573@quack.suse.cz> <20140920154733.GM2832@worktop.localdomain> <1411229447.24444.53.camel@joe-AO725> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.24; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 20 Sep 2014 09:10:47 -0700 Joe Perches wrote: > On Sat, 2014-09-20 at 17:47 +0200, Peter Zijlstra wrote: > > On a whole, printk() is entirely useless for debugging these days, its > > far too fragile/unreliable to be taken seriously so I really don't care > > on that point either. > > That's unfortunate. > > Care to enumerate the issues that you believe make > printk too fragile/unreliable for debugging? I seldom use printk these days. It's far too limited in its uses. For one, most things worth debugging happen thousands of times a second, and printk will just slow things down to a crawl if it is used. Another, is that it can not be used in most critical sections (NMI handlers and anything that deals with the scheduler). Also, as it no longer blocks when another CPU is doing a printk, a bug can happen which crashes the system and the output of that bug will never get printed due to the delayed output from another CPU having the console lock. -- Steve