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Subject[PATCH] perf stat: Poll for monitored tasks being alive in fork mode
Date
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.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
---
tools/perf/builtin-stat.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 63a3afc..71f3bc8 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -553,6 +553,13 @@ 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) &&
+ (child_pid != -1)) {
+ kill(child_pid, SIGTERM);
+ break;
+ }
+
nanosleep(&ts, NULL);
if (timeout)
break;
--
2.7.4
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