linux-kernel - Re: [PATCH 2/3] ring-buffer: rename debugfs file tracing_on to writing

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Date:	Tue, 6 Jan 2009 14:47:40 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, fweisbec@...il.com,
	roel.kluin@...il.com, pq@....fi, srostedt@...hat.com
Subject: Re: [PATCH 2/3] ring-buffer: rename debugfs file tracing_on to
 writing_enabled

On Tue, 06 Jan 2009 17:33:39 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: Steven Rostedt <srostedt@...hat.com>
> 
> Impact: clean up
> 
> The debugfs file name tracing_on is confusing since there is also
> a tracing_enabled. When a tracer is added to current_tracer and
> tracing_enabled is set to 1, then the tracer will start tracing.
> The current file tracing_on, if set to 1, will allow writing to
> the ring buffers. If tracing_on is set to 0 then the ring buffers
> are read only, and any attempt by the tracers to write to the
> ring buffers will fail.
> 
> But the name tracing_on confuses both developers and users.
> This patch renames it to 'writing_enabled'.  This is exactly what
> the file does. When set to 1, the ring buffers have writing enabled
> and when set to 0, the ring buffers can not be written to.
> 
> The tracers do not get any call backs called or other notification
> that the ring buffers have been set to read only, except when they
> attempt to write to the ring buffers, that write will fail.
> 
> Note: it is a requirement that any tracer that uses the ring buffers
> must handle a failure to write to the ring buffers, since the ring buffers
> may be disabled for any number of reasons.
> 
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> ---
>  kernel/trace/ring_buffer.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index a9d9760..dba6876 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -2514,10 +2514,11 @@ static __init int rb_init_debugfs(void)
>  
>  	d_tracer = tracing_init_dentry();
>  
> -	entry = debugfs_create_file("tracing_on", 0644, d_tracer,
> +	entry = debugfs_create_file("writing_enabled", 0644, d_tracer,
>  				    &ring_buffer_flags, &rb_simple_fops);
>  	if (!entry)
> -		pr_warning("Could not create debugfs 'tracing_on' entry\n");
> +		pr_warning("Could not create debugfs"
> +			   " 'writing_enabled' entry\n");
>  
>  	return 0;
>  }

There's no corresponding documentation update needed?
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