Re: [PATCH v2 2/2] trace-cmd: Clear error log on reset subcommand

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 19 Feb 2020 15:14:10 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> The "trace-cmd reset" command is supposed to set the ftrace state to default.
> However, the ftrace error logs are not reseted.
> A logic is added to delete the content of "error_log" file when "trace-cmd reset" is executed.
> 
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
> ---
>  tracecmd/trace-record.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
> index b6a412e..3e0d066 100644
> --- a/tracecmd/trace-record.c
> +++ b/tracecmd/trace-record.c
> @@ -4638,6 +4638,25 @@ static void clear_triggers(void)
>  		clear_instance_triggers(instance);
>  }
>  
> +static void clear_instance_error_log(struct buffer_instance *instance)
> +{
> +	char *file;
> +
> +	file = tracefs_instance_get_file(instance->tracefs, "error_log");
> +	if (!file)
> +		return;
> +	write_file(file, " ");
> +	tracefs_put_tracing_file(file);
> +}

The error_log file is not guaranteed to exist. Please add a check for
existence via stat() (hmm, perhaps we should make a file_exists() helper
function). Otherwise I get this:

# trace-cmd reset
trace-cmd: No such file or directory
  opening to '/debug/tracing/error_log'


> +
> +static void clear_error_log(void)
> +{
> +	struct buffer_instance *instance;
> +
> +	for_all_instances(instance)
> +		clear_instance_error_log(instance);
> +}
> +
>  static void clear_all_synth_events(void)
>  {
>  	char sevent[BUFSIZ];
> @@ -5382,6 +5401,7 @@ void trace_reset(int argc, char **argv)
>  	clear_filters();
>  	clear_triggers();
>  	clear_all_synth_events();
> +	clear_error_log();
>  	/* set clock to "local" */
>  	reset_clock();
>  	reset_event_pid();