linux-kernel - Re: [PATCH] tracing: fix missing osnoise tracer on max

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Date:   Sun, 19 Sep 2021 12:01:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jackie Liu <liu.yun@...ux.dev>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org, bristot@...hat.com
Subject: Re: [PATCH] tracing: fix missing osnoise tracer on max_latency

On Sat, 18 Sep 2021 13:11:18 +0800
Jackie Liu <liu.yun@...ux.dev> wrote:

> From: Jackie Liu <liuyun01@...inos.cn>
> 
> The compiler warns when the data are actually unused:
> 
>   kernel/trace/trace.c:1712:13: error: ‘trace_create_maxlat_file’ defined but not used [-Werror=unused-function]
>    1712 | static void trace_create_maxlat_file(struct trace_array *tr,
>         |             ^~~~~~~~~~~~~~~~~~~~~~~~
> 
> [Why]
> CONFIG_HWLAT_TRACER=n, CONFIG_TRACER_MAX_TRACE=n, CONFIG_OSNOISE_TRACER=y
> gcc report warns.
> 
> [How]
> Now trace_create_maxlat_file will only take effect when
> CONFIG_HWLAT_TRACER=y or CONFIG_TRACER_MAX_TRACE=y. In fact, after
> adding osnoise trace, it also needs to take effect.
> 
> BTW, Fixed the conflicting defined comment information.

Thanks for the report.

> 
> Fixes: bce29ac9ce0b ("trace: Add osnoise tracer")
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Signed-off-by: Jackie Liu <liuyun01@...inos.cn>
> ---
>  kernel/trace/trace.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 7896d30d90f7..d7e3ed82fafd 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1744,11 +1744,7 @@ void latency_fsnotify(struct trace_array *tr)
>  	irq_work_queue(&tr->fsnotify_irqwork);
>  }
>  
> -/*
> - * (defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)) && \
> - *  defined(CONFIG_FSNOTIFY)
> - */
> -#else
> +#else /* LATENCY_FS_NOTIFY */
>  
>  #define trace_create_maxlat_file(tr, d_tracer)				\
>  	trace_create_file("tracing_max_latency", 0644, d_tracer,	\

To clean this up even better, we should add here:

#elif defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
	|| defined(CONFIG_OSNOISE_TRACER)

#  define trace_create_maxlat_file(tr, d_tracer)			\
	trace_create_file("tracing_max_latency", 0644, d_tracer,	\
			  &tr->max_latency, &tracing_max_lat_fops)

#else
# define trace_create_maxlat_file(tr, d_tracer)	 do { } while (0)
#endif

> @@ -9473,7 +9469,8 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
>  
>  	create_trace_options_dir(tr);
>  
> -#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)
> +#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
> +	|| defined(CONFIG_OSNOISE_TRACER)

And remove the #if statement complete from inside the function.

-- Steve

>  	trace_create_maxlat_file(tr, d_tracer);
>  #endif
>