Re: [PATCH 2/2] perf tests: add test for trace output loss

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Thu, Nov 14, 2024 at 09:44:56AM -0800, Benjamin Peterson wrote:
> > On Thu, Nov 14, 2024 at 02:37:52PM -0300, Arnaldo Carvalho de Melo wrote:
> > diff --git a/tools/perf/tests/shell/trace_exit_race.sh b/tools/perf/tests/shell/trace_exit_race.sh
> > index 8b70324bc5b4fb4c..c37ed6bb9f7e8fab 100755
> > --- a/tools/perf/tests/shell/trace_exit_race.sh
> > +++ b/tools/perf/tests/shell/trace_exit_race.sh
> > @@ -12,10 +12,10 @@
> >  skip_if_no_perf_trace || exit 2

> >  trace_shutdown_race() {
> > -       for i in $(seq 100); do
> > +       for _ in $(seq 100); do
> >                 perf trace -e syscalls:sys_enter_exit_group true 2>>$file
> >         done
> > -       [ $(grep -c -E " +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$" $file) = "100" ]
> > +       [ "$(grep -c -E ' +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$' $file)" = "100" ]
> >  }
 
> This all looks okay.

The test is failing for me as there is garbage in the output of perf
trace even with Namhyung having already applied your previous patch:

⬢ [acme@toolbox perf-tools-next]$ git log --oneline --author benjamin@engflow.com
12bd434f68ea45c7 (HEAD -> perf-tools-next) perf tests: Add test for 'perf trace' output loss
efbcd2cd7eac10a9 perf trace: Do not lose last events in a race
5fb8e56542a3cf46 (perf-tools-next/tmp.perf-tools-next) perf trace: avoid garbage when not printing a trace event's arguments
⬢ [acme@toolbox perf-tools-next]$

root@number:~# perf trace -e syscalls:sys_enter_exit_group true
     0.000 true/1982428 syscalls:sys_enter_exit_group( k?m)
root@number:~# perf trace -e syscalls:sys_enter_exit_group true
     0.000 true/1982430 syscalls:sys_enter_exit_group()
root@number:~# perf trace -e syscalls:sys_enter_exit_group true
     0.000 true/1982432 syscalls:sys_enter_exit_group()
root@number:~# perf trace -e syscalls:sys_enter_exit_group true
     0.000 true/1982434 syscalls:sys_enter_exit_group()
root@number:~# perf trace -e syscalls:sys_enter_exit_group true
     0.000 true/1982437 syscalls:sys_enter_exit_group( k�)
root@number:~# perf trace -e syscalls:sys_enter_exit_group true
     0.000 true/1982439 syscalls:sys_enter_exit_group(, loads 8��1)
root@number:~#

So we don't _miss_ the events, which I was noticing and brought me to
test your latest 2 patches, which I applied and added a Tested-by, now
tryint to figure out this garbage...

- Arnaldo