linux-kernel - Re: [PATCH 2/7] blktrace: make blk_tracer

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Date:	Fri, 20 Mar 2009 09:47:12 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Jens Axboe <jens.axboe@...cle.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] blktrace: make blk_tracer_enabled a bool flag

On Fri, Mar 20, 2009 at 09:48:03AM +0800, Li Zefan wrote:
> It doesn't have to be a counter, and it can be a bool flag instead.
> 
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> ---
>  kernel/trace/blktrace.c |   12 +++---------
>  1 files changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index fb3bc53..73845b7 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -30,7 +30,7 @@
>  static unsigned int blktrace_seq __read_mostly = 1;
>  
>  static struct trace_array *blk_tr;
> -static int __read_mostly  blk_tracer_enabled;
> +static bool blk_tracer_enabled __read_mostly;
>  
>  /* Select an alternative, minimalistic output than the original one */
>  #define TRACE_BLK_OPT_CLASSIC	0x1
> @@ -1111,9 +1111,7 @@ static int blk_tracer_init(struct trace_array *tr)
>  {
>  	blk_tr = tr;
>  	blk_tracer_start(tr);
> -	mutex_lock(&blk_probe_mutex);
> -	blk_tracer_enabled++;
> -	mutex_unlock(&blk_probe_mutex);
> +	blk_tracer_enabled = true;
>  	return 0;
>  }
>  
> @@ -1131,11 +1129,7 @@ static void blk_tracer_reset(struct trace_array *tr)
>  	if (!atomic_read(&blk_probes_ref))
>  		return;
>  
> -	mutex_lock(&blk_probe_mutex);
> -	blk_tracer_enabled--;
> -	WARN_ON(blk_tracer_enabled < 0);
> -	mutex_unlock(&blk_probe_mutex);
> -
> +	blk_tracer_enabled = false;
>  	blk_tracer_stop(tr);
>  }
>  
> -- 
> 1.5.4.rc3


Looks good.
Indeed the init() and reset() callbacks are not supposed to be called nested.

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