[LTP] [PATCH v3, 2/2] cgroup/cgroup_regression_test: Fix umount failure

[xuyang2018.jy@fujitsu.com]

Hi Leo
> 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 on certain platform.
>
> The reason is that this test sequence would have the chance of
> missing a release code path when doing rmdir and umount.
>
> Adding a little delay between "rmdir" and "umount" could fix the problem,
> so use tst_umount API instead of umount in "rmdir, umount" sequence.
>
> Fixes: #839
>
> Signed-off-by: Leo Yu-Chi Liang<ycliang@andestech.com>
> ---
>   .../controllers/cgroup/cgroup_regression_test.sh       | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh b/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh
> index 1f7f3820e..056166f11 100755
> --- a/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh
> +++ b/testcases/kernel/controllers/cgroup/cgroup_regression_test.sh
> @@ -145,7 +145,7 @@ test2()
>   	fi
>
>   	rmdir cgroup/0 cgroup/1
> -	umount cgroup/
With adding a comment like
# Avoid possible EBUSY error

so when other converts this case into new api, they will keep to use 
tst_umount.

Reviewed-by: Yang Xu <xuyang2018.jy@fujitsu.com>
> +	tst_umount cgroup/
>   }
>
>   #---------------------------------------------------------------------------
> @@ -193,7 +193,7 @@ test3()
>   	wait $pid2 2>/dev/null
>
>   	rmdir $cpu_subsys_path/0 2>  /dev/null
> -	umount cgroup/ 2>  /dev/null
> +	tst_umount cgroup/ 2>  /dev/null
>   	check_kernel_bug
>   }
>
> @@ -222,7 +222,7 @@ test4()
>   	mount -t cgroup -o none,name=foo cgroup cgroup/
>   	mkdir cgroup/0
>   	rmdir cgroup/0
> -	umount cgroup/
> +	tst_umount cgroup/
here as well
>
>   	if dmesg | grep -q "MAX_LOCKDEP_SUBCLASSES too low"; then
>   		tst_res TFAIL "lockdep BUG was found"
> @@ -254,7 +254,7 @@ test5()
>   	mount -t cgroup none cgroup 2>  /dev/null
>   	mkdir cgroup/0
>   	rmdir cgroup/0
> -	umount cgroup/ 2>  /dev/null
> +	tst_umount cgroup/ 2>  /dev/null
>   	check_kernel_bug
>   }
>
> @@ -290,7 +290,7 @@ test6()
>
>   	mount -t cgroup -o ns xxx cgroup/>  /dev/null 2>&1
>   	rmdir cgroup/[1-9]*>  /dev/null 2>&1
> -	umount cgroup/
> +	tst_umount cgroup/
here as well
>   	check_kernel_bug
>   }
>