Messages in this thread | | | Subject | Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode | From | "Jin, Yao" <> | Date | Sun, 6 Jan 2019 22:02:18 +0800 |
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On 1/6/2019 9:25 PM, Jiri Olsa wrote: > On Sat, Jan 05, 2019 at 11:16:40AM +0800, Jin, Yao wrote: >> >> >> On 1/4/2019 8:54 PM, Jiri Olsa wrote: >>> On Fri, Jan 04, 2019 at 10:28:17AM +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. >>>> >>>> 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)) { >>> >>> do we need that child_pid check? we just returned from waitpid >>> so we should be ok.. we just make the race window smaller >>> >>> could we just do: >>> >>> if (!is_target_alive(&target, evsel_list->threads)) { >>> kill(child_pid, SIGTERM); >>> break; >>> } >>> >> >> I think this code should be OK and I have tested yet. I have a question >> about the race condition, we really don't need a lock to protect the >> child_pid? >> >> skip_signal() >> { >> /* >> * render child_pid harmless >> * won't send SIGTERM to a random >> * process in case of race condition >> * and fast PID recycling >> */ >> child_pid = -1; >> } >> >> __run_perf_stat() >> { >> .... >> kill(child_pid, SIGTERM); >> } >> >> If child_pid is set by -1 in a small window between checking of child_pid >> and kill(), then kill(-1, SIGTERM) may happen. All processes except the kill >> process itself and init would receive SIGTERM. > > ah right, -1 is special.. however that can still happen also > in the orginal patch.. how about we do something like below > > jirka > > > --- > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index acfd48db52dd..c322cb271180 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -583,6 +583,14 @@ 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; >
Hi Jiri,
I think your patch is good. At least, we can avoid the case of kill(-1, SIGTERM).
BTW, you post this patch or I re-post it, both fine for me. :)
Thanks Jin Yao
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