[LTP] [PATCH 1/1] cgroup/cgroup_regression_test: Fix umount failure

[Leo Liang <ycliang@andestech.com>]

From a151d48235629a125d5db57dd76c96fd951d5293 Mon Sep 17 00:00:00 2001
From: Leo Yu-Chi Liang <ycliang@andestech.com>
Date: Mon, 28 Jun 2021 11:05:54 +0800
Subject: [PATCH 1/1] cgroup/cgroup_regression_test: Fix umount failure

The test sequence
	mount -t cgroup -o <controllers> <path>
	mkdir <path>/<dir>
	rmdir <path>/<dir>
	umount <path>
	mount -t cgroup -o <controllers> <path>
would easily fail at the last mount with -EBUSY.

The reason is that this test sequence have the chance of
missing a release code path when doing rmdir and umount.

Add sync between every "rmdir, umount" pair to fix the problem.

Fixes: #839

Signed-off-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
 .../kernel/controllers/cgroup/cgroup_regression_test.sh    | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh b/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh
index 1f7f3820e..9a00df101 100755
--- a/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh
+++ b/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh
@@ -145,6 +145,7 @@ test2()
 	fi
 
 	rmdir cgroup/0 cgroup/1
+	sync
 	umount cgroup/
 }
 
@@ -193,6 +194,7 @@ test3()
 	wait $pid2 2>/dev/null
 
 	rmdir $cpu_subsys_path/0 2> /dev/null
+	sync
 	umount cgroup/ 2> /dev/null
 	check_kernel_bug
 }
@@ -222,6 +224,7 @@ test4()
 	mount -t cgroup -o none,name=foo cgroup cgroup/
 	mkdir cgroup/0
 	rmdir cgroup/0
+	sync
 	umount cgroup/
 
 	if dmesg | grep -q "MAX_LOCKDEP_SUBCLASSES too low"; then
@@ -254,6 +257,7 @@ test5()
 	mount -t cgroup none cgroup 2> /dev/null
 	mkdir cgroup/0
 	rmdir cgroup/0
+	sync
 	umount cgroup/ 2> /dev/null
 	check_kernel_bug
 }
@@ -290,6 +294,7 @@ test6()
 
 	mount -t cgroup -o ns xxx cgroup/ > /dev/null 2>&1
 	rmdir cgroup/[1-9]* > /dev/null 2>&1
+	sync
 	umount cgroup/
 	check_kernel_bug
 }
@@ -324,6 +329,7 @@ test_7_1()
 	mkdir $subsys_path/0
 	sleep 100 < $subsys_path/0 &	# add refcnt to this dir
 	rmdir $subsys_path/0
+	sync
 
 	# remount with new subsystems added
 	# since 2.6.28, this remount will fail
@@ -349,6 +355,7 @@ test_7_2()
 	mkdir cgroup/0
 	sleep 100 < cgroup/0 &	# add refcnt to this dir
 	rmdir cgroup/0
+	sync
 
 	# remount with some subsystems removed
 	# since 2.6.28, this remount will fail
-- 
2.17.0