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

[Martin Doucha]

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>
---

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