On Mon, Jan 07, 2019 at 09:00:50AM +0800, Jin Yao wrote:
> Following test shows the stat keeps running even if no longer
> task to monitor (mgen exits at ~5s).
>
> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
> time counts unit events
> 1.000148916 1,308,365,864 cycles
> 2.000379171 1,297,269,875 cycles
> 3.000556719 1,297,187,078 cycles
> 4.000914241 761,261,827 cycles
> 5.001306091 <not counted> cycles
> 6.001676881 <not counted> cycles
> 7.002046336 <not counted> cycles
> 8.002405651 <not counted> cycles
> 9.002766625 <not counted> cycles
> 10.001395827 <not counted> cycles
>
> We'd better finish stat immediately if there's no longer task to
> monitor.
>
> After:
>
> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10
> time counts unit events
> 1.000180062 1,236,592,661 cycles
> 2.000421539 1,223,733,572 cycles
> 3.000609910 1,297,047,663 cycles
> 4.000807545 1,297,215,816 cycles
> 5.001001578 1,297,208,032 cycles
> 6.001390345 582,343,659 cycles
> sleep: Terminated
>
> Now the stat exits immediately when the monitored tasks ends.
>
> v2:
> ---
> There is a potential race condition window, that is the
> child_pid set with -1 and kill(-1, SIGTERM) may happen.
> Jiri provides a simple method which stores the child_pid to
> a local variable and check the local variable before kill().
> At least, we can avoid the kill(-1, SIGTERM) case.
>
> Signed-off-by: Jin Yao <yao....@linux.intel.com>
Reviewed-by: Jiri Olsa <jo...@kernel.org>
thanks,
jirka
> ---
> tools/perf/builtin-stat.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 63a3afc..bd5fb8e 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -553,6 +553,15 @@ static int __run_perf_stat(int argc, const char **argv,
> int run_idx)
>
> if (interval || timeout) {
> while (!waitpid(child_pid, &status, WNOHANG)) {
> + if (!is_target_alive(&target,
> + evsel_list->threads)) {
> + int pid = child_pid;
> +
> + if (pid != -1)
> + kill(pid, SIGTERM);
> + break;
> + }
> +
> nanosleep(&ts, NULL);
> if (timeout)
> break;
> --
> 2.7.4
>
