linux-kernel - Re: [PATCH 1/2] perf: Iterate on tep event arrays directly

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Date:   Thu, 17 Oct 2019 18:24:31 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linux-trace-devel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tzvetomir Stoyanov <tstoyanov@...are.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 1/2] perf: Iterate on tep event arrays directly

Em Thu, Oct 17, 2019 at 05:05:22PM -0400, Steven Rostedt escreveu:
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> Instead of calling a useless (and broken) helper function to get the next
> event of a tep event array, just get the array directly and iterate over it.
> 
> Note, the broken part was from trace_find_next_event() which after this will
> no longer be used, and can be removed.
> 
> Link: http://lkml.kernel.org/r/20191017153733.630cd5eb@gandalf.local.home

I'll add a:

Fixes: bb3dd7e7c4d5 ("tools lib traceevent, perf tools: Move struct tep_handler definition in a local header file")
Cc: stable@...r.kernel.org : v4.20+

As this is when this problem starts causing the segfault when generating
python scripts from perf.data files with multiple tracepoint events, ok?

- Arnaldo
 
> Reported-by: Daniel Bristot de Oliveira <bristot@...hat.com>
> Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  tools/perf/util/scripting-engines/trace-event-perl.c   | 8 ++++++--
>  tools/perf/util/scripting-engines/trace-event-python.c | 9 +++++++--
>  2 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/scripting-engines/trace-event-perl.c b/tools/perf/util/scripting-engines/trace-event-perl.c
> index 15961854ba67..741f040648b5 100644
> --- a/tools/perf/util/scripting-engines/trace-event-perl.c
> +++ b/tools/perf/util/scripting-engines/trace-event-perl.c
> @@ -539,10 +539,11 @@ static int perl_stop_script(void)
>  
>  static int perl_generate_script(struct tep_handle *pevent, const char *outfile)
>  {
> +	int i, not_first, count, nr_events;
> +	struct tep_event **all_events;
>  	struct tep_event *event = NULL;
>  	struct tep_format_field *f;
>  	char fname[PATH_MAX];
> -	int not_first, count;
>  	FILE *ofp;
>  
>  	sprintf(fname, "%s.pl", outfile);
> @@ -603,8 +604,11 @@ sub print_backtrace\n\
>  }\n\n\
>  ");
>  
> +	nr_events = tep_get_events_count(pevent);
> +	all_events = tep_list_events(pevent, TEP_EVENT_SORT_ID);
>  
> -	while ((event = trace_find_next_event(pevent, event))) {
> +	for (i = 0; all_events && i < nr_events; i++) {
> +		event = all_events[i];
>  		fprintf(ofp, "sub %s::%s\n{\n", event->system, event->name);
>  		fprintf(ofp, "\tmy (");
>  
> diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
> index 5d341efc3237..93c03b39cd9c 100644
> --- a/tools/perf/util/scripting-engines/trace-event-python.c
> +++ b/tools/perf/util/scripting-engines/trace-event-python.c
> @@ -1687,10 +1687,11 @@ static int python_stop_script(void)
>  
>  static int python_generate_script(struct tep_handle *pevent, const char *outfile)
>  {
> +	int i, not_first, count, nr_events;
> +	struct tep_event **all_events;
>  	struct tep_event *event = NULL;
>  	struct tep_format_field *f;
>  	char fname[PATH_MAX];
> -	int not_first, count;
>  	FILE *ofp;
>  
>  	sprintf(fname, "%s.py", outfile);
> @@ -1735,7 +1736,11 @@ static int python_generate_script(struct tep_handle *pevent, const char *outfile
>  	fprintf(ofp, "def trace_end():\n");
>  	fprintf(ofp, "\tprint(\"in trace_end\")\n\n");
>  
> -	while ((event = trace_find_next_event(pevent, event))) {
> +	nr_events = tep_get_events_count(pevent);
> +	all_events = tep_list_events(pevent, TEP_EVENT_SORT_ID);
> +
> +	for (i = 0; all_events && i < nr_events; i++) {
> +		event = all_events[i];
>  		fprintf(ofp, "def %s__%s(", event->system, event->name);
>  		fprintf(ofp, "event_name, ");
>  		fprintf(ofp, "context, ");
> -- 
> 2.23.0
> 

-- 

- Arnaldo