Messages in this thread Patch in this message | | | From | Jin Yao <> | Subject | [PATCH v2] Poll for monitored tasks being alive in fork mode | Date | Mon, 7 Jan 2019 09:00:50 +0800 |
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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.jin@linux.intel.com> --- 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
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