From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754641AbYCVURA (ORCPT ); Sat, 22 Mar 2008 16:17:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751388AbYCVUQv (ORCPT ); Sat, 22 Mar 2008 16:16:51 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:39484 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751281AbYCVUQu (ORCPT ); Sat, 22 Mar 2008 16:16:50 -0400 Date: Sat, 22 Mar 2008 16:16:48 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Pekka Paalanen cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: tracing and mmiotrace In-Reply-To: <20080322173245.01e69743@daedalus.pq.iki.fi> Message-ID: References: <20080321233955.66e75a57@daedalus.pq.iki.fi> <20080322120746.GF13264@elte.hu> <20080322173245.01e69743@daedalus.pq.iki.fi> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pekka, I'm on vacation at the moment, but will start up helping Ingo with ftrace on Monday. On Sat, 22 Mar 2008, Pekka Paalanen wrote: > > > > that's weird - _entry_ is NULL? > > Yes. See the patch, and my kernel log at > http://jumi.lut.fi/~paalanen/scratch/tracing-dmesg1.txt > > First you see my check in __trace_special() trigger, and then NULL > pointer dereference BUG at ffffffff80259332 which translates to > kernel/trace/trace.c:639 in tracing_generic_entry_update(), line: > entry->preempt_count = pc & 0xff; > I don't understand why it tries to dereference NULL even when I > check for it. Interesting. I'll have to look into that more on Monday. > > --- > Oh, and during bootup there is an error about -fstack-protector-all > test failed. > > > > btw. currently 'cat /debug/tracing/trace' gives the > > > print_func_help_header() and quits, it never stays waiting for more > > > data. > > > > yeah - try "cat /debug/tracing/trace_pipe" for the waiting variant - > > does that work better? > > Not really. IIRC it said "resource temporarily unavailable" until > mmiotrace actually tried to produce data. No header there. So I > cannot make "cat" ready to read and after that start tracing. I'll have to clean up the trace_pipe code to be a bit more robust. Thanks for doing this. I'll be getting more involved starting Monday. -- Steve