linux-kernel - Re: [PATCH 00/15] [git pull] for tip/tracing/ftrace

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Message-ID: <20090218005133.GH25856@elte.hu>
Date:	Wed, 18 Feb 2009 01:51:33 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 00/15] [git pull] for tip/tracing/ftrace


* Sam Ravnborg <sam@...nborg.org> wrote:

> On Tue, Feb 17, 2009 at 07:49:49AM -0500, Steven Rostedt wrote:
> > 
> > On Tue, 17 Feb 2009, Ingo Molnar wrote:
> > 
> > > 
> > > * Steven Rostedt <rostedt@...dmis.org> wrote:
> > > 
> > > > Ingo,
> > > > 
> > > > This is a patch series that offers a variety of features.
> > > > 
> > > > The first is to add:
> > > > 
> > > >  #### all functions enabled ####
> > > > 
> > > > to set_ftrace_filter when all functions will be traced when function
> > > > tracing is on.
> > > > 
> > > > The next is to add a :command: interface, and the module command:
> > > > 
> > > >  echo '*:mod:ext4' > set_ftrace_filter
> > > > 
> > > > Will select all functions in the ext4 module.
> > > > 
> > > >  echo '!*write*:mod:ext4' > set_ftrace_filter
> > > > 
> > > > will remove all functions with the characters 'write' and are
> > > > in ext4.
> > > 
> > > Very nice feature!
> > > 
> > > I'm wondering, would it be possible to somehow extend this to 
> > > built-in drivers too, so that we get symmetry of usage 
> > > independently of whether something is built in or a module? I 
> > > suspect it needs some extensions to kbuild though ...
> > 
> > Yeah, that may needs some kbuild magic.
> 
> I have not followed this thread.
> What kind of magic do you have in mind?

It would be nice to have a notion of 'modules' even for built-in 
drivers - at least as far as symbol lookups go.

It would allow such a module-specific trigger:

    echo '!*write*:mod:ext4' > set_ftrace_filter

to work even if ext4 is built-in.

	Ingo
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