[PATCH cgroup/for-next v2 0/2] cpuset: fix failure to enable isolated partition when containing isolcpus

[PATCH cgroup/for-next v2 0/2] cpuset: fix failure to enable isolated partition when containing isolcpus

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

This series fixes an issue where enabling an isolated partition fails if
the cpuset contains isolcpus. Additionally, the patches include
modifications to address a potential related issue.

---
Changes from v1:
- patch1: update the fixed commit id.

Chen Ridong (2):
  cpuset: fix failure to enable isolated partition when containing
    isolcpus
  cpuset: Use new excpus for nocpu error check when enabling root
    partition

 kernel/cgroup/cpuset.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

-- 
2.34.1

[PATCH cgroup/for-next v2 1/2] cpuset: fix failure to enable isolated partition when containing isolcpus

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

The 'isolcpus' parameter specified at boot time can be assigned to an
isolated partition. While it is valid put the 'isolcpus' in an isolated
partition, attempting to change a member cpuset to an isolated partition
will fail if the cpuset contains any 'isolcpus'.

For example, the system boots with 'isolcpus=9', and the following
configuration works correctly:

  # cd /sys/fs/cgroup/
  # mkdir test
  # echo 1 > test/cpuset.cpus
  # echo isolated > test/cpuset.cpus.partition
  # cat test/cpuset.cpus.partition
  isolated
  # echo 9 > test/cpuset.cpus
  # cat test/cpuset.cpus.partition
  isolated
  # cat test/cpuset.cpus
  9

However, the following steps to convert a member cpuset to an isolated
partition will fail:

  # cd /sys/fs/cgroup/
  # mkdir test
  # echo 9 > test/cpuset.cpus
  # echo isolated > test/cpuset.cpus.partition
  # cat test/cpuset.cpus.partition
  isolated invalid (partition config conflicts with housekeeping setup)

The issue occurs because the new partition state (new_prs) is used for
validation against housekeeping constraints before it has been properly
updated. To resolve this, move the assignment of new_prs before the
housekeeping validation check when enabling a root partition.

Fixes: 4a74e418881f ("cgroup/cpuset: Check partition conflict with housekeeping setup")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 44231cb1d83f..2b7e2f17577e 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1806,6 +1806,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 		xcpus = tmp->delmask;
 		if (compute_excpus(cs, xcpus))
 			WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
+		new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
 
 		/*
 		 * Enabling partition root is not allowed if its
@@ -1838,7 +1839,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 
 		deleting = true;
 		subparts_delta++;
-		new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
 	} else if (cmd == partcmd_disable) {
 		/*
 		 * May need to add cpus back to parent's effective_cpus
-- 
2.34.1

Re: [PATCH cgroup/for-next v2 1/2] cpuset: fix failure to enable isolated partition when containing isolcpus

[Waiman Long]

On 9/18/25 9:12 PM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
>
> The 'isolcpus' parameter specified at boot time can be assigned to an
> isolated partition. While it is valid put the 'isolcpus' in an isolated
> partition, attempting to change a member cpuset to an isolated partition
> will fail if the cpuset contains any 'isolcpus'.
>
> For example, the system boots with 'isolcpus=9', and the following
> configuration works correctly:
>
>    # cd /sys/fs/cgroup/
>    # mkdir test
>    # echo 1 > test/cpuset.cpus
>    # echo isolated > test/cpuset.cpus.partition
>    # cat test/cpuset.cpus.partition
>    isolated
>    # echo 9 > test/cpuset.cpus
>    # cat test/cpuset.cpus.partition
>    isolated
>    # cat test/cpuset.cpus
>    9
>
> However, the following steps to convert a member cpuset to an isolated
> partition will fail:
>
>    # cd /sys/fs/cgroup/
>    # mkdir test
>    # echo 9 > test/cpuset.cpus
>    # echo isolated > test/cpuset.cpus.partition
>    # cat test/cpuset.cpus.partition
>    isolated invalid (partition config conflicts with housekeeping setup)
>
> The issue occurs because the new partition state (new_prs) is used for
> validation against housekeeping constraints before it has been properly
> updated. To resolve this, move the assignment of new_prs before the
> housekeeping validation check when enabling a root partition.
>
> Fixes: 4a74e418881f ("cgroup/cpuset: Check partition conflict with housekeeping setup")
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 44231cb1d83f..2b7e2f17577e 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1806,6 +1806,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   		xcpus = tmp->delmask;
>   		if (compute_excpus(cs, xcpus))
>   			WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
> +		new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
>   
>   		/*
>   		 * Enabling partition root is not allowed if its
> @@ -1838,7 +1839,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   
>   		deleting = true;
>   		subparts_delta++;
> -		new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
>   	} else if (cmd == partcmd_disable) {
>   		/*
>   		 * May need to add cpus back to parent's effective_cpus
Reviewed-by: Waiman Long <longman@redhat.com>

[PATCH cgroup/for-next v2 2/2] cpuset: Use new excpus for nocpu error check when enabling root partition

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

A previous patch fixed a bug where new_prs should be assigned before
checking housekeeping conflicts. This patch addresses another potential
issue: the nocpu error check currently uses the xcpus which is not updated.
Although no issue has been observed so far, the check should be performed
using the new effective exclusive cpus.

The comment has been removed because the function returns an error if
nocpu checking fails, which is unrelated to the parent.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
---
 kernel/cgroup/cpuset.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 2b7e2f17577e..44d65890326a 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1818,11 +1818,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 		if (prstate_housekeeping_conflict(new_prs, xcpus))
 			return PERR_HKEEPING;
 
-		/*
-		 * A parent can be left with no CPU as long as there is no
-		 * task directly associated with the parent partition.
-		 */
-		if (nocpu)
+		if (tasks_nocpu_error(parent, cs, xcpus))
 			return PERR_NOCPUS;
 
 		/*
-- 
2.34.1

Re: [PATCH cgroup/for-next v2 0/2] cpuset: fix failure to enable isolated partition when containing isolcpus

[Tejun Heo]

On Fri, Sep 19, 2025 at 01:12:25AM +0000, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
> 
> This series fixes an issue where enabling an isolated partition fails if
> the cpuset contains isolcpus. Additionally, the patches include
> modifications to address a potential related issue.
> 
> ---
> Changes from v1:
> - patch1: update the fixed commit id.
> 
> Chen Ridong (2):
>   cpuset: fix failure to enable isolated partition when containing
>     isolcpus
>   cpuset: Use new excpus for nocpu error check when enabling root
>     partition

Applied to cgroup/for-6.18.

Thanks.

-- 
tejun