From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753178Ab1KPUNH (ORCPT ); Wed, 16 Nov 2011 15:13:07 -0500 Received: from he.sipsolutions.net ([78.46.109.217]:39926 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751599Ab1KPUNG (ORCPT ); Wed, 16 Nov 2011 15:13:06 -0500 Subject: Re: [PATCH] tracing: add trace console From: Johannes Berg To: Steven Rostedt Cc: Christoph Hellwig , LKML , Frederic Weisbecker , Ingo Molnar In-Reply-To: <1321473443.4181.38.camel@frodo> References: <1321438728.4773.16.camel@jlt3.sipsolutions.net> <20111116151037.GA26166@infradead.org> <1321456652.4502.12.camel@jlt3.sipsolutions.net> <1321461693.4181.26.camel@frodo> <1321461902.4502.14.camel@jlt3.sipsolutions.net> <1321462856.4181.28.camel@frodo> <1321468380.4502.16.camel@jlt3.sipsolutions.net> <1321473443.4181.38.camel@frodo> Content-Type: text/plain; charset="UTF-8" Date: Wed, 16 Nov 2011 21:12:59 +0100 Message-ID: <1321474379.4502.17.camel@jlt3.sipsolutions.net> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-11-16 at 14:57 -0500, Steven Rostedt wrote: > On Wed, 2011-11-16 at 19:33 +0100, Johannes Berg wrote: > > On Wed, 2011-11-16 at 12:00 -0500, Steven Rostedt wrote: > > > On Wed, 2011-11-16 at 17:45 +0100, Johannes Berg wrote: > > > > > > > I briefly looked at it just after writing the email, but quickly got > > > > lost in printk.c because of the multi-line handling it has. We could > > > > instead trace each call to printk(), so the multi-line stuff would end > > > > up in multiple events, but all of that code is too much vodoo for me :) > > > > > > Here's what can go into printk.c: > > > > > > diff --git a/kernel/printk.c b/kernel/printk.c > > > index 1455a0d..4b8445a 100644 > > > --- a/kernel/printk.c > > > +++ b/kernel/printk.c > > > @@ -542,6 +542,7 @@ MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to" > > > static void _call_console_drivers(unsigned start, > > > unsigned end, int msg_log_level) > > > { > > > + trace_console(&LOG_BUF(start), end - start); > > > if ((msg_log_level < console_loglevel || ignore_loglevel) && > > > console_drivers && start != end) { > > > if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { > > > > > > > > > And then you can make a TRACE_EVENT(console) that takes a buffer and a > > > len, and write that to the ring buffer. > > > > Yes, of course, but if we're going to modify the code then I thought we > > should probably trace everything independent of the console printk > > level. > > > > This will trace everything independent from the console level. Noticed > that I put the tracepoint before the msg_log_level is checked. D'oh, right. Yeah that seems good. Too bad I discarded my previous attempt already :) johannes