[LTP] [PATCH v2] test_children_cleanup.sh: Fix race condition

[Li Wang]

On Tue, Feb 15, 2022 at 6:20 PM Martin Doucha <mdoucha@suse.cz> wrote:

> Processes can stay alive for a short while even after receiving SIGKILL.
> Give the child in subprocess cleanup libtest up to 5 seconds to fully exit
> or change state to zombie before reporting that it was left behind.
>
> Signed-off-by: Martin Doucha <mdoucha@suse.cz>
>
Reviewed-by: Li Wang <liwang@redhat.com>


> ---
>
> Changes since v1: Report success even if the child gets stuck in zombie
> state
>
>  lib/newlib_tests/test_children_cleanup.sh | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/lib/newlib_tests/test_children_cleanup.sh
> b/lib/newlib_tests/test_children_cleanup.sh
> index 4b4e8b2f0..23408c1bc 100755
> --- a/lib/newlib_tests/test_children_cleanup.sh
> +++ b/lib/newlib_tests/test_children_cleanup.sh
> @@ -10,10 +10,21 @@ rm "$TMPFILE"
>  if [ "x$CHILD_PID" = "x" ]; then
>         echo "TFAIL: Child process was not created"
>         exit 1
> -elif ! kill -s 0 $CHILD_PID &>/dev/null; then
> -       echo "TPASS: Child process was cleaned up"
> -       exit 0
> -else
> -       echo "TFAIL: Child process was left behind"
> -       exit 1
>  fi
> +
> +# The child process can stay alive for a short while even after receiving
> +# SIGKILL, especially if the system is under heavy load. Wait up to 5
> seconds
> +# for it to fully exit.
> +for i in `seq 6`; do
> +       CHILD_STATE=`sed -ne 's/^State:\s*\([A-Z]\).*$/\1/p'
> "/proc/$CHILD_PID/status" 2>/dev/null`
> +
> +       if [ ! -e "/proc/$CHILD_PID" ] || [ "x$CHILD_STATE" = "xZ" ]; then
> +               echo "TPASS: Child process was cleaned up"
> +               exit 0
> +       fi
> +
> +       sleep 1
> +done
> +
> +echo "TFAIL: Child process was left behind"
> +exit 1
> --
> 2.34.1
>
>

-- 
Regards,
Li Wang
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