linux-kernel - Re: [PATCH v3 11/12] tracing: guard tracing_selftest_disabled by CONFIG_FTRACE_STARTUP

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Date:	Tue, 02 Jul 2013 19:56:43 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
Cc:	fweisbec@...il.com, mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 11/12] tracing: guard tracing_selftest_disabled by
 CONFIG_FTRACE_STARTUP_TEST

On Wed, 2013-04-10 at 11:26 +0800, zhangwei(Jovi) wrote:
> From: "zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
> 
> Variable tracing_selftest_disabled have not any sense when
> CONFIG_FTRACE_STARTUP_TEST is disabled.
> 
> This patch also remove __read_mostly attribute, since variable
> tracing_selftest_disabled really not read mostly.

Yes it is mostly read only. Sure, it's not read much, but it is also
only written to once. That makes it, "read mostly".

-- Steve

> 
> Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@...wei.com>
> ---
>  kernel/trace/trace.c        |    6 ++++--
>  kernel/trace/trace.h        |    2 +-
>  kernel/trace/trace_events.c |    2 ++
>  3 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index ee4e110..09a3aa8 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -58,10 +58,12 @@ bool ring_buffer_expanded;
>   */
>  static bool __read_mostly tracing_selftest_running;
>  
> +#ifdef CONFIG_FTRACE_STARTUP_TEST
>  /*
>   * If a tracer is running, we do not want to run SELFTEST.
>   */
> -bool __read_mostly tracing_selftest_disabled;
> +bool tracing_selftest_disabled;
> +#endif
>  
>  /* For tracers that don't implement custom flags */
>  static struct tracer_opt dummy_tracer_opt[] = {
> @@ -1069,8 +1071,8 @@ int register_tracer(struct tracer *type)
>  	tracing_set_tracer(type->name);
>  	default_bootup_tracer = NULL;
>  	/* disable other selftests, since this will break it. */
> -	tracing_selftest_disabled = true;
>  #ifdef CONFIG_FTRACE_STARTUP_TEST
> +	tracing_selftest_disabled = true;
>  	printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
>  	       type->name);
>  #endif
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 9b8afa7..e9ef8b7 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -546,10 +546,10 @@ extern int DYN_FTRACE_TEST_NAME(void);
>  extern int DYN_FTRACE_TEST_NAME2(void);
>  
>  extern bool ring_buffer_expanded;
> -extern bool tracing_selftest_disabled;
>  DECLARE_PER_CPU(int, ftrace_cpu_disabled);
>  
>  #ifdef CONFIG_FTRACE_STARTUP_TEST
> +extern bool tracing_selftest_disabled;
>  extern int trace_selftest_startup_function(struct tracer *trace,
>  					   struct trace_array *tr);
>  extern int trace_selftest_startup_function_graph(struct tracer *trace,
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 7c52a51..7c4a16b 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -2251,7 +2251,9 @@ static __init int setup_trace_event(char *str)
>  {
>  	strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
>  	ring_buffer_expanded = true;
> +#ifdef CONFIG_FTRACE_STARTUP_TEST
>  	tracing_selftest_disabled = true;
> +#endif
>  
>  	return 1;
>  }


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