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Date: Wed, 18 Feb 2009 01:51:33 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Peter Zijlstra <peterz@infradead.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 00/15] [git pull] for tip/tracing/ftrace
Message-ID: <20090218005133.GH25856@elte.hu>
References: <20090217051227.957864159@goodmis.org> <20090217104213.GC6602@elte.hu> <alpine.DEB.1.10.0902170747160.910@gandalf.stny.rr.com> <20090218004127.GB30812@uranus.ravnborg.org>
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* Sam Ravnborg <sam@ravnborg.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@goodmis.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