github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-28 03:52:02 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict

Browse Source 
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 86888c7bd1 ("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: 86888c7bd1 ("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>
This commit is contained in:
Hui Peng 2026-09-24 04:27:27 +00:00 committed by Tejun Heo
parent 1765a153d9
commit 31c88350b7
2 changed files with 4 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
kernel/cgroup/cpuset.c
View File

@ -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))

2
tools/testing/selftests/cgroup/test_cpuset_prs.sh
View File

@ -298,6 +298,8 @@ TEST_MATRIX=(
" C0-4:X2-4 C1-4:X2-4:P2 C2-4:X4:P1 \
. . . X1 . 0 A1:0-1|A2:2-4|A3:2-4 \
A1:P0|A2:P2|A3:P-1 2-4"
" CX1-3:P1 CX1-3 CX1-3 . . . P1 . 0 A1:1-3|A2:1-3|A3:1-3 \
A1:P1|A2:P0|A3:P-1"
# Remote partition offline tests
" C0-3 C1-3 C2-3 . X2-3 X2-3 X2-3:P2:O2=0 . 0 A1:0-1|A2:1|A3:3 A1:P0|A3:P2 2-3"