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

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

[Andrea Cervesato]

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>


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

[linuxtestproject.agent]

Hi Andrea,

On Thu, 11 Jun 2026 17:03:41 +0200, Andrea Cervesato wrote:
> cgroup_fj: don't disable controller that was already enabled

Verdict: Reviewed

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

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

[Wei Gao via ltp]

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

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Re: [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
>

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

[Andrea Cervesato via ltp]

Merged, Thanks!

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

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