linux-kernel - Re: [PATCH v2 0/4] ftrace: important updates

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Message-ID: <20090107094905.GB16025@elte.hu>
Date:	Wed, 7 Jan 2009 10:49:05 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Roel Kluin <roel.kluin@...il.com>, Pekka Paalanen <pq@....fi>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 0/4] ftrace: important updates


* Steven Rostedt <rostedt@...dmis.org> wrote:

> Ingo,
> 
> The first patch is a critical fix that needs to get into 2.6.29.
> 
> The next patch is a rename of tracing_on to writing_enabled since
> tracing_on is confusing, and the file enables or disables writes.
> 
> The last patch is a fix to tip that prevents a memory leak.
> 
> This version I added some clean ups that Andrew Morton suggested.
> I know you did not pull the previous version, because I forgot
> to push the changes to kernel.org ;-)
> 
> The following patches are in:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
> 
>     branch: tip/devel
> 
> 
> Frederic Weisbecker (1):
>       tracing/ftrace: fix a memory leak in stat tracing
> 
> Steven Rostedt (3):
>       ftrace: convert unsigned index to signed
>       trace: clean up funny line breaks in stat_seq_show

pulled most of it, thanks Steve, except this bit:

>       ring-buffer: rename debugfs file tracing_on to writing_enabled

writing_enabled is at least as confusing as tracing_on - if not more so.

The user really does not care about all the deeper machinery that happens 
in ftrace - the difference between a 'light' disabling of a tracer and a 
'heavy' disabling of a tracer (which means it unregisters itself 
completely in essence).

To resolve this, we should probably hide this difference altogether (as i 
have suggested to do many months ago, when this first came up), by 
removing tracing_enabled.

A tracer can still be fully unregistered: by simply switching the current 
tracer to the 'nop' tracer. tracing_on/off remains the lightweight version 
that most users are interested in anyway.

	Ingo
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