linux-kernel - Re: [PATCH v2 05/15] perf ftrace: factor out function write_tracing_file

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Date:   Wed, 8 Jul 2020 20:53:46 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Changbin Du <changbin.du@...il.com>, Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/15] perf ftrace: factor out function
 write_tracing_file_int()

On Tue, Jul 07, 2020 at 12:09:23PM -0400, Steven Rostedt wrote:
> On Sat, 27 Jun 2020 21:36:44 +0800
> Changbin Du <changbin.du@...il.com> wrote:
> 
> > We will reuse this function later.
> > 
> 
> BTW, trace-cmd.git now has a libtracefs.so library, which I'm hoping
> within a month to have as a stand alone (probably along with
> libtraceevent and even a libtracecmd).
> 
>   https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/tree/lib/tracefs
> 
> This is a library made to interact with the tracefs directory to remove
> reimplementing it all over the place.
>
Nice! This will make implementing a tracing tool much simpler. Look forward
to seeing it appears in most Linux distributions.

> -- Steve
> 
> 
> 
> > Signed-off-by: Changbin Du <changbin.du@...il.com>
> > ---
> >  tools/perf/builtin-ftrace.c | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index dceae70c3a22..003efa756322 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -166,6 +166,17 @@ static int read_tracing_file_to_stdout(const char *name)
> >  	return ret;
> >  }
> >  
> > +static int write_tracing_file_int(const char *name, int value)
> > +{
> > +	char buf[16];
> > +
> > +	snprintf(buf, sizeof(buf), "%d", value);
> > +	if (write_tracing_file(name, buf) < 0)
> > +		return -1;
> > +
> > +	return 0;
> > +}
> > +
> >  static int reset_tracing_cpu(void);
> >  static void reset_tracing_filters(void);
> >  
> > @@ -296,8 +307,6 @@ static void reset_tracing_filters(void)
> >  
> >  static int set_tracing_depth(struct perf_ftrace *ftrace)
> >  {
> > -	char buf[16];
> > -
> >  	if (ftrace->graph_depth == 0)
> >  		return 0;
> >  
> > @@ -306,9 +315,7 @@ static int set_tracing_depth(struct perf_ftrace *ftrace)
> >  		return -1;
> >  	}
> >  
> > -	snprintf(buf, sizeof(buf), "%d", ftrace->graph_depth);
> > -
> > -	if (write_tracing_file("max_graph_depth", buf) < 0)
> > +	if (write_tracing_file_int("max_graph_depth", ftrace->graph_depth) < 0)
> >  		return -1;
> >  
> >  	return 0;
> 

-- 
Cheers,
Changbin Du