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

[Petr Vorel <pvorel@suse.cz>]

> 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/
> +	tst_umount cgroup/
As I note in previous patch, with suggested change to tst_umount() to always add
trailing "/" it'd be enough just "tst_umount cgroup".

I'm not sure what is better: automatic handling or having to explicitly add
trailing "/".

Kind regards,
Petr

>  }

>  #---------------------------------------------------------------------------
> @@ -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/

>  	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/
>  	check_kernel_bug
>  }