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

[Joerg Vehlow]

Hi,

On 6/28/2021 5:30 AM, Leo Liang wrote:
>  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
I would like a short comment close to the syncs. When I converted 
cpuset_regression_test.sh, I would have removed the sync in there, if 
there wouldn't have been any comment.
Most of the time syncs are not required and just added by paranoid 
developers, but if there is a real reason, I think it should be stated 
in a comment.

Jörg