[LTP] [PATCH] cgroup_fj: don't disable controller that was already enabled

[Sebastian Chlad]

On Fri, 12 Jun 2026 at 11:04, Wei Gao via ltp <ltp@lists.linux.it> wrote:

> On Thu, Jun 11, 2026 at 05:03:41PM +0200, Andrea Cervesato wrote:
> > From: Andrea Cervesato <andrea.cervesato@suse.com>
> >
> > On immutable distributions (and systemd-managed systems in general)
> > the cpuset controller is typically already enabled at the root cgroup
> > level. The cleanup tried to unconditionally disable it via
> > subtree_control, which failed with EBUSY because other system cgroups
> > were still using it, producing a spurious TWARN.
> >
> > Save whether the controller was already enabled at root before
> > cgroup_require and skip the root-level disable in cleanup when it
> > was.
> >
> > Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> > ---
> >  testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh | 10
> +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
> b/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
> > index
> 153d351d7936effb15527620f565acaaed7ac747..8b5e73466ba32d2c66a2805a03f4d2136c16509b
> 100755
> > --- a/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
> > +++ b/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
> > @@ -57,6 +57,14 @@ create_subgroup()
> >
> >  common_setup()
> >  {
> > +    # Check if the controller is already enabled at root before
> > +    # cgroup_require potentially enables it, so that cleanup does
> > +    # not disable a controller the system was already using.
> > +    if [ -f /sys/fs/cgroup/cgroup.subtree_control ] && \
> > +       grep -qw "$subsystem" /sys/fs/cgroup/cgroup.subtree_control; then
> > +        ctrl_was_enabled=1
> > +    fi
> > +
> >      cgroup_require "$subsystem"
> >      mount_point=$(cgroup_get_mountpoint "$subsystem")
> >      start_path=$(cgroup_get_test_path "$subsystem")
> > @@ -77,7 +85,7 @@ common_cleanup()
> >
> >      cgroup_cleanup
> >
> > -    if [ "$cgroup_version" = "2" ]; then
> > +    if [ "$cgroup_version" = "2" ] && [ "$ctrl_was_enabled" != "1" ];
> then
> >          case "$subsystem" in
> >          cpu|io|memory|pids)
> >              :;;
> >
> > ---
> > base-commit: a375e8deed471723f5a0114c56eb48fe6f6f45d3
> > change-id: 20260611-fix_cgroup_immutable-2259f7591f8d
> >
> > Best regards,
> > --
> > Andrea Cervesato <andrea.cervesato@suse.com>
> Reviewed-by: Wei Gao <wegao@suse.com>
>

Feel free to add:
Reviewed-by: Sebastian Chlad <sebastian.chlad@suse.com>


> >
> >
> > --
> > Mailing list info: https://lists.linux.it/listinfo/ltp
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>