linux-kernel - Re: [PATCH v1 5/5] perf test: Make daemon signal test less racy

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Date: Tue, 23 Jan 2024 16:02:23 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Ravi Bangoria <ravi.bangoria@....com>, 
	Ross Zwisler <zwisler@...omium.org>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, 
	Shirisha G <shirisha@...ux.ibm.com>, Kajol Jain <kjain@...ux.ibm.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/5] perf test: Make daemon signal test less racy

On Mon, Jan 22, 2024 at 4:06 PM Ian Rogers <irogers@...gle.com> wrote:
>
> The daemon signal test sends signals and then expects files to be
> written. It was observed on an Intel Alderlake that the signals were
> sent too quickly leading to the 3 expected files not appearing. To
> avoid this send the next signal only after the expected previous file
> has appeared. To avoid an infinite loop the number of retries is
> limited.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/tests/shell/daemon.sh | 34 ++++++++++++++++++++++----------
>  1 file changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/tools/perf/tests/shell/daemon.sh b/tools/perf/tests/shell/daemon.sh
> index 4c598cfc5afa..de61e7898578 100755
> --- a/tools/perf/tests/shell/daemon.sh
> +++ b/tools/perf/tests/shell/daemon.sh
> @@ -414,16 +414,30 @@ EOF
>         # start daemon
>         daemon_start ${config} test
>
> -       # send 2 signals
> -       perf daemon signal --config ${config} --session test
> -       perf daemon signal --config ${config}
> -
> -       # stop daemon
> -       daemon_exit ${config}
> -
> -       # count is 2 perf.data for signals and 1 for perf record finished
> -       count=`ls ${base}/session-test/*perf.data* | wc -l`
> -       if [ ${count} -ne 3 ]; then
> +        # send 2 signals then exit. Do this in a loop watching the number of
> +        # files to avoid races. If the loop retries more than 600 times then
> +        # give up.
> +       local retries=0
> +       local signals=0
> +       local success=0
> +       while [ ${retries} -lt 600 ] && [ ${success} -eq 0 ]; do
> +               local files
> +               files=`ls ${base}/session-test/*perf.data* | wc -l`

Wouldn't it show error messages for 'file not found' for the first
round?  I think we can add '2> /dev/null' to suppress that.

Thanks,
Namhyung


> +               if [ ${signals} -eq 0 ]; then
> +                       perf daemon signal --config ${config} --session test
> +                       signals=1
> +               elif [ ${signals} -eq 1 ] && [ $files -ge 1 ]; then
> +                       perf daemon signal --config ${config}
> +                       signals=2
> +               elif [ ${signals} -eq 2 ] && [ $files -ge 2 ]; then
> +                       daemon_exit ${config}
> +                       signals=3
> +               elif [ ${signals} -eq 3 ] && [ $files -ge 3 ]; then
> +                       success=1
> +               fi
> +               retries=$((${retries} +1))
> +       done
> +       if [ ${success} -eq 0 ]; then
>                 error=1
>                 echo "FAILED: perf data no generated"
>         fi
> --
> 2.43.0.429.g432eaa2c6b-goog
>