lkml.org 
[lkml]   [2019]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] 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.

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
\
 
 \ /
  Last update: 2019-01-07 02:02    [W:0.036 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site