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| author | Hui Peng <benquike@gmail.com> | 2026-09-24 04:27:27 +0000 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-09-26 08:07:26 -1000 |
| commit | 31c88350b7dd1522792f726f79607f31bb55c50f (patch) | |
| tree | 178864e68d77a689ee0e94de38d977bedf6ea93e /kernel | |
| parent | 1765a153d985c231357145e26798f9408db10e42 (diff) | |
| download | linux-next-31c88350b7dd1522792f726f79607f31bb55c50f.tar.gz linux-next-31c88350b7dd1522792f726f79607f31bb55c50f.zip | |
cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict
When a remote partition is created underneath an existing local partition
via a non-partition (PRS_MEMBER) intermediate cgroup, update_prstate() sees
parent->partition_root_state == PRS_MEMBER and calls
remote_partition_enable().
Commit 86888c7bd117 ("cgroup/cpuset: Add warnings to catch inconsistency
in exclusive CPUs") replaced the cpumask_intersects(tmp->new_cpus,
subpartitions_cpus) error check in remote_partition_enable() with
WARN_ON_ONCE(). As a result, remote_partition_enable() emits a warning
and proceeds to enable the remote partition on CPUs that are already
owned by the ancestor local partition in subpartitions_cpus.
This can be reproduced on Linux 7.3.0-rc3 with:
mkdir -p /tmp/cg1
mount -t cgroup2 none /tmp/cg1
echo "+cpuset" > /tmp/cg1/cgroup.subtree_control
mkdir /tmp/cg1/A
echo 1 > /tmp/cg1/A/cpuset.cpus
echo 1 > /tmp/cg1/A/cpuset.cpus.exclusive
echo root > /tmp/cg1/A/cpuset.cpus.partition
echo "+cpuset" > /tmp/cg1/A/cgroup.subtree_control
mkdir /tmp/cg1/A/B
echo 1 > /tmp/cg1/A/B/cpuset.cpus
echo 1 > /tmp/cg1/A/B/cpuset.cpus.exclusive
echo "+cpuset" > /tmp/cg1/A/B/cgroup.subtree_control
mkdir /tmp/cg1/A/B/D
echo 1 > /tmp/cg1/A/B/D/cpuset.cpus
echo 1 > /tmp/cg1/A/B/D/cpuset.cpus.exclusive
echo root > /tmp/cg1/A/B/D/cpuset.cpus.partition
which triggers:
WARNING: kernel/cgroup/cpuset.c:1594 at remote_partition_enable+0x1c1/0x300
and leaves both /tmp/cg1/A and /tmp/cg1/A/B/D as active root partitions
claiming exclusive CPU 1.
Fix this by returning PERR_NOCPUS when tmp->new_cpus intersects
subpartitions_cpus in remote_partition_enable(), matching the error code
used by remote_cpus_update() for the same subpartitions_cpus conflict, and
add a regression test case to
tools/testing/selftests/cgroup/test_cpuset_prs.sh.
Tested in QEMU on Linux 7.3.0-rc3 using the reproducer above and
tools/testing/selftests/cgroup/test_cpuset_prs.sh.
Fixes: 86888c7bd117 ("cgroup/cpuset: Add warnings to catch inconsistency in exclusive CPUs")
Suggested-by: Guopeng Zhang <guopeng.zhang@linux.dev>
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Hui Peng <benquike@gmail.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup/cpuset.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 8f24171b6055..1fcec89a28b9 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1591,10 +1591,11 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs, * above it or remote partition root underneath it is not allowed. */ compute_excpus(cs, tmp->new_cpus); - WARN_ON_ONCE(cpumask_intersects(tmp->new_cpus, subpartitions_cpus)); if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) || cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus)) return PERR_INVCPUS; + if (cpumask_intersects(tmp->new_cpus, subpartitions_cpus)) + return PERR_NOCPUS; if (((new_prs == PRS_ISOLATED) && !isolated_cpus_can_update(tmp->new_cpus, NULL)) || prstate_housekeeping_conflict(new_prs, tmp->new_cpus)) |