Re: [PATCH] tracing: fix missing osnoise tracer on max_latency

From: Steven Rostedt
Date: Sun Sep 19 2021 - 12:01:50 EST


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

> From: Jackie Liu <liuyun01@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx>
> ---
> 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
>