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SubjectRe: [PATCH] perf script: fix crash when processing recorded stat data
On Sun, Jan 20, 2019 at 11:14:14AM -0800, Tony Jones wrote:
> While updating Perf to work with Python3 and Python2 I noticed that the
> stat-cpi script was dumping core.
>
> $ perf stat -e cycles,instructions record -o /tmp/perf.data /bin/false
>
> Performance counter stats for '/bin/false':
>
> 802,148 cycles
>
> 604,622 instructions 802,148 cycles
> 604,622 instructions
>
> 0.001445842 seconds time elapsed
>
> $ perf script -i /tmp/perf.data -s scripts/python/stat-cpi.py
> Segmentation fault (core dumped)
> ...
> ...
> rblist=rblist@entry=0xb2a200 <rt_stat>,
> new_entry=new_entry@entry=0x7ffcb755c310) at util/rblist.c:33
> ctx=<optimized out>, type=<optimized out>, create=<optimized out>,
> cpu=<optimized out>, evsel=<optimized out>) at util/stat-shadow.c:118
> ctx=<optimized out>, type=<optimized out>, st=<optimized out>)
> at util/stat-shadow.c:196
> count=count@entry=727442, cpu=cpu@entry=0, st=0xb2a200 <rt_stat>)
> at util/stat-shadow.c:239
> config=config@entry=0xafeb40 <stat_config>,
> counter=counter@entry=0x133c6e0) at util/stat.c:372
> ...
> ...
>
> The issue is that since 1fcd03946b52 perf_stat__update_shadow_stats now calls
> update_runtime_stat passing rt_stat rather than calling update_stats but
> perf_stat__init_shadow_stats has never been called to initialize rt_stat in
> the script path processing recorded stat data.
>
> Since I can't see any reason why perf_stat__init_shadow_stats() is presently
> initialized like it is in builtin-script.c::perf_sample__fprint_metric()
> [4bd1bef8bba2f] I'm proposing it instead be initialized once in __cmd_script
>
> Fixes: 1fcd03946b52 ("perf stat: Update per-thread shadow stats")
> Signed-off-by: Tony Jones <tonyj@suse.de>
> ---
> tools/perf/builtin-script.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index d079f36d342d..9a6dd86e606f 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -1681,13 +1681,8 @@ static void perf_sample__fprint_metric(struct perf_script *script,
> .force_header = false,
> };
> struct perf_evsel *ev2;
> - static bool init;
> u64 val;
>
> - if (!init) {
> - perf_stat__init_shadow_stats();
> - init = true;
> - }

well, there's no need to use shadow stats until stat
data is processed.. but it's actually just a static
initialization, so there's no need for late init

Reviewed-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka

> if (!evsel->stats)
> perf_evlist__alloc_stats(script->session->evlist, false);
> if (evsel_script(evsel->leader)->gnum++ == 0)
> @@ -2359,6 +2354,8 @@ static int __cmd_script(struct perf_script *script)
>
> signal(SIGINT, sig_handler);
>
> + perf_stat__init_shadow_stats();
> +
> /* override event processing functions */
> if (script->show_task_events) {
> script->tool.comm = process_comm_event;
> --
> 2.18.0
>

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