/usr/share/bcc/tools/trace cannot exit from loops

[realhezhe]

On python 3.8.5 and kernel 5.8
root@intel-x86-64:~# /usr/share/bcc/tools/trace do_sys_openat2 -M 1
PID TID COMM FUNC
179 179 systemd-journal do_sys_openat2
Exception ignored on calling ctypes callback function: <function PerfEventArray.open_perf_buffer..raw_cb at 0x7f2a75f060d0>
Traceback (most recent call last):
File "/usr/lib64/python3.8/site-packages/bcc/table.py", line 685, in raw_cb_
callback(cpu, data, size)
File "/usr/share/bcc/tools/trace", line 630, in print_event
exit()
File "/usr/lib64/python3.8/_sitebuiltins.py", line 26, in call
raise SystemExit(code)
SystemExit: None
The above repeated endlessly

The following change could make it work, but not sure if it's the best way to do.

diff --git a/tools/trace.py b/tools/trace.py
index 7a61594f..d09dd2a8 100755
--- a/tools/trace.py
+++ b/tools/trace.py
@@ -627,7 +627,7 @@ BPF_PERF_OUTPUT(%s);
Probe.event_count += 1
if Probe.max_events is not None and
Probe.event_count >= Probe.max_events:
"- exit()"
"+ os._exit(0)"
sys.stdout.flush()

" def attach(self, bpf, verbose):"

[yonghong-song]

Maybe sys.exit()?

[yonghong-song]

It does not fail in my environment with python 3.7

$ sudo trace.py do_sys_openat2 -M 1 
PID     TID     COMM            FUNC             
117055  117055  tmux: server    do_sys_openat2

Do you know why it fails? Maybe due to python site packages?
https://www.geeksforgeeks.org/python-exit-commands-quit-exit-sys-exit-and-os-_exit/

[realhezhe]

sys.exit() and other way would trigger the same call trace.
Seems due to new python update. But it's not easy for me to turn between versions. I'll try.

[nurdann]

This could be related to #4649