[tip:perf/urgent] perf stat: Poll for monitored tasks being alive

[tip-bot for Jiri Olsa]

Commit-ID:  cbb5df7e96070f1f728ff7885443646ebba703d4
Gitweb:     https://git.kernel.org/tip/cbb5df7e96070f1f728ff7885443646ebba703d4
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Mon, 22 Oct 2018 11:30:15 +0200
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 22 Oct 2018 12:37:52 -0300

perf stat: Poll for monitored tasks being alive

Adding the check for tasks we monitor via -p/-t options, and finish stat
if there's no longer task to monitor.

Requested-by: Stephane Eranian <eranian@xxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20181022093015.9106-1-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-stat.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

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 @@ try_again:
 		enable_counters();
 		while (!done) {
 			nanosleep(&ts, NULL);
+			if (!is_target_alive(&target, evsel_list->threads))
+				break;
 			if (timeout)
 				break;
 			if (interval) {