linux-kernel - Re: [PATCH 3/9 - v2][RFC] tracing: Remove per event trace registering

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Message-ID: <20100507145438.GB29573@Krystal>
Date:	Fri, 7 May 2010 10:54:38 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Christoph Hellwig <hch@....de>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/9 - v2][RFC] tracing: Remove per event trace
	registering

* Frederic Weisbecker (fweisbec@...il.com) wrote:
> On Mon, May 03, 2010 at 11:40:48PM -0400, Steven Rostedt wrote:
> > From: Steven Rostedt <srostedt@...hat.com>
> > 
> > This patch removes the register functions of TRACE_EVENT() to enable
> > and disable tracepoints. The registering of a event is now down
> > directly in the trace_events.c file. The tracepoint_probe_register()
> > is now called directly.
> > 
> > The prototypes are no longer type checked, but this should not be
> > an issue since the tracepoints are created automatically by the
> > macros. If a prototype is incorrect in the TRACE_EVENT() macro, then
> > other macros will catch it.
> 
> 
> 
> Agreed. Typechecking matters for human code but not in this context.
> Considering that the tracepoint and the probe are created by the same
> CPP code, bugs will be tracked down quickly and located to a single
> place.

So it seems that I am the only one asking for extra type-checking and
caring about problems that can appear subtily on architectures where the
number of caller/callee arguments must match. And also the only one
considering that passing more arguments to a callback that does not
expect all of them might be a problem on some architectures.

Am I the only one thinking there is something fishy there ? I might be
entirely over-paranoid, but this approach has rarely failed me in the
past.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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