Messages in this thread | | | From | Stephane Eranian <> | Date | Tue, 16 Oct 2018 11:10:12 -0700 | Subject | Re: [BUG] perf stat: hangs with -p and process completes |
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Jiri,
Thanks for looking into this. Yeah, I don't think you need a kernel patch to make this work. You can poll in the app. Let me try this out.
On Tue, Oct 16, 2018 at 9:25 AM Jiri Olsa <jolsa@redhat.com> wrote: > > On Tue, Oct 16, 2018 at 01:03:41PM +0200, Jiri Olsa wrote: > > On Fri, Oct 12, 2018 at 02:26:09PM -0700, Stephane Eranian wrote: > > > Hi, > > > > > > I am running into a perf stat issue with the -p option which allows you > > > to attach to a running process. If that process happens to terminate > > > while under monitoring > > > perf hangs in there and never terminates. The proper behavior would be to stop. > > > I can see the issue in that the attached process is not a child, so > > > wait() would not work. > > > > > > To reproduce: > > > $ sleep 10 & > > > $ perf stat -p $! > > > > > > doing the same with perf record works, so there is a solution to this problem. > > > > yea, we don't poll for the event state change in perf stat, > > but we do that in perf record.. also because the perf poll > > code in kernel is originaly meant for tracking the ring > > buffer state > > > > maybe we could return EPOLLIN for alive events without ring > > buffer.. like below (totaly untested) and add polling for > > event state into perf stat > > > > cc-ing perf folks > > > > on the second thought attached patch works as well > without kernel change > > jirka > > > --- > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index b86aba1c8028..d1028d7755bb 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -409,6 +409,28 @@ static struct perf_evsel *perf_evsel__reset_weak_group(struct perf_evsel *evsel) > return leader; > } > > +static bool is_target_alive(struct target *_target, > + struct thread_map *threads) > +{ > + struct stat st; > + int i; > + > + if (!target__has_task(_target)) > + return true; > + > + for (i = 0; i < threads->nr; i++) { > + char path[PATH_MAX]; > + > + scnprintf(path, PATH_MAX, "%s/%d", procfs__mountpoint(), > + threads->map[i].pid); > + > + if (!stat(path, &st)) > + return true; > + } > + > + return false; > +} > + > static int __run_perf_stat(int argc, const char **argv, int run_idx) > { > int interval = stat_config.interval; > @@ -579,6 +601,8 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx) > enable_counters(); > while (!done) { > nanosleep(&ts, NULL); > + if (!is_target_alive(&target, evsel_list->threads)) > + break; > if (timeout) > break; > if (interval) {
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