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

[Petr Vorel]

Hi all,

...
> It doesn't work for all platforms and we can not guarantee how long it will
> cost before PID 1 reaps zombie process.

> Also, I just get to know that  Docker does not run processes under a
> special init process that properly reaps child processes, so that it is
> possible for the container to end up with zombie processes that cause
> all sorts of trouble.

> I even try adding `kill -SIGCHLD 1` but does not work as expected.

> See CI jobs:
>   https://github.com/wangli5665/ltp/runs/5194270998?check_suite_focus=true
> <https://mail.google.com/mail/u/1/%E2%80%8Bhttps://github.com/wangli5665/ltp/runs/5194270998?check_suite_focus=true>

> Therefore, I suggest giving a chance to my refined patch V2 :).

> --- a/lib/newlib_tests/test_children_cleanup.sh
> +++ b/lib/newlib_tests/test_children_cleanup.sh
> @@ -10,10 +10,16 @@ rm "$TMPFILE"
>  if [ "x$CHILD_PID" = "x" ]; then
>         echo "TFAIL: Child process was not created"
>         exit 1
> +elif grep -q "Z (zombie)" /proc/$CHILD_PID/status; then
> +       echo "TPASS: Child process is in zombie state"
> +       exit 0
>  elif ! kill -s 0 $CHILD_PID &>/dev/null; then
>         echo "TPASS: Child process was cleaned up"
>         exit 0
>  else
>         echo "TFAIL: Child process was left behind"
> +       echo "cat /proc/$CHILD_PID/status"
> +       echo "---------------------------"
> +       cat /proc/$CHILD_PID/status
>         exit 1
>  fi

Li's approach LGTM.

Kind regards,
Petr