From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751519AbaLNRHg (ORCPT ); Sun, 14 Dec 2014 12:07:36 -0500 Received: from smtprelay0113.hostedemail.com ([216.40.44.113]:40456 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750918AbaLNRHf (ORCPT ); Sun, 14 Dec 2014 12:07:35 -0500 X-Session-Marker: 6E657665747340676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:2693:3138:3139:3140:3141:3142:3292:3353:3622:3865:3866:3867:3868:3870:3871:3872:3874:4250:5007:6261:7875:7903:9010:10004:10400:10848:10967:11232:11658:11914:12296:12517:12519:12663:12740:13069:13311:13357:14096:14097:21080,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0 X-HE-Tag: crime99_7c36c98594363 X-Filterd-Recvd-Size: 2454 Date: Sun, 14 Dec 2014 12:07:32 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton , Thomas Gleixner , Mathieu Desnoyers , "Paul E. McKenney" Subject: Re: [PATCH 0/3] tracing: Enable tracepoints early and allow printk to use them Message-ID: <20141214120732.2503f6b0@gandalf.local.home> In-Reply-To: <20141214164104.307127356@goodmis.org> References: <20141214164104.307127356@goodmis.org> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 14 Dec 2014 11:41:04 -0500 Steven Rostedt wrote: > As the merge window is still open, and this code was not as complex > as I thought it might be. I'm thinking of pushing this in now. > > This will allow Thomas to debug his irq work for 3.20. Bah, my cover letters have sucked lately. Let me explain what this patch set does. It basically adds two new features. 1) Allow traceopoints to be enabled right after mm_init(). By passing in the trace_event= kernel command line parameter, tracepoints can be enabled at boot up. For debugging things like the initialization of interrupts, it is needed to have tracepoints enabled very early. People have asked about this before and this has been on my todo list. As it can be helpful for Thomas to debug his upcoming 3.20 IRQ work, I'm pushing this now. This way he can add tracepoints into the IRQ set up and have have users enable them when things go wrong. 2) Have the tracepoints printed via printk() (the console) when they are triggered. If the irq code locks up or reboots the box, having the tracepoint output go into the kernel ring buffer is useless for debugging. But being able to add the tp_printk kernel command line option along with the trace_event= option will have these tracepoints printed as they occur, and that can be really useful for debugging early lock up or reboot problems. -- Steve