linux-kernel - Re: [PATCH] Linux Kernel Markers 0.2 for Linux 2.6.17

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Date:	Tue, 19 Sep 2006 15:13:20 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	"Randy.Dunlap" <rdunlap@...otime.net>
Cc:	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Douglas Niehaus <niehaus@...s.ku.edu>,
	Tom Zanussi <zanussi@...ibm.com>,
	Paul Mundt <lethal@...ux-sh.org>, Jes Sorensen <jes@....com>,
	Richard J Moore <richardj_moore@...ibm.com>,
	William Cohen <wcohen@...hat.com>,
	"Martin J. Bligh" <mbligh@...igh.org>,
	Michel Dagenais <michel.dagenais@...ymtl.ca>,
	systemtap@...rces.redhat.com, ltt-dev@...fik.org
Subject: Re: [PATCH] Linux Kernel Markers 0.2 for Linux 2.6.17

Hi Randy,

Thanks for the comments, see below :

* Randy.Dunlap (rdunlap@...otime.net) wrote:
> > +static inline void __mark_check_format(const char *fmt, ...)
> > +	__attribute__ ((format (printf, 1, 2)));
> > +void __mark_check_format(const char *fmt, ...) {  }
> 
> That last line is confusing (to me).  What's it for?
> Is it just an empty (inline) function definition?
> If so, why repeat the void + function name?
> 

The goal of this "empty" function is just to have to compiler check the string
format consistency.

I separated the function declaration and implementation because I have seen some
compilers complain about having the two merged together.

I will change it to

static inline __attribute__ ((format (printf, 1, 2)))
void __mark_check_format(const char *fmt, ...)
{ }

And hope every compiler will like it.

The empty implementation is because the function is called (must therefore be
implemented), but I expect the compiler to completely optimize it away.

> > --- /dev/null
> > +++ b/kernel/Kconfig.marker
> > @@ -0,0 +1,75 @@
> > +# Code markers configuration
> > +
> > +menu "Marker configuration"
> > +
> > +
> > +config MARK
> > +	bool "Enable MARK code markers"
> > +	default y
> 
> Please justify using 'y' as the default value.
> 

It has to be debated. The default for markers will put a symbol for all the
markers, so that kprobe can easily attach to it. It has no impact that I am
aware of except to boost the number of symbols.

Mathieu

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