From: Guopeng Zhang <[email protected]>
An invalid local partition can become valid again even when its
exclusive CPUs are no longer available from its parent.
This can be reproduced on a cgroup v2 system with CPUs 0-7 online:
cd /sys/fs/cgroup
echo +cpuset > cgroup.subtree_control
mkdir A
echo 1-4 > A/cpuset.cpus
echo 1-4 > A/cpuset.cpus.exclusive
echo root > A/cpuset.cpus.partition
echo +cpuset > A/cgroup.subtree_control
mkdir A/B
echo 3-4 > A/B/cpuset.cpus
echo 3-4 > A/B/cpuset.cpus.exclusive
echo root > A/B/cpuset.cpus.partition
echo 1-2 > A/cpuset.cpus.exclusive
cat A/B/cpuset.cpus.partition
root
cat A/B/cpuset.cpus.exclusive.effective
cat A/cpuset.cpus.effective
1-2
cat A/B/cpuset.cpus.effective
1-2
B is changed back to a valid root even though its exclusive CPUs are
no longer available and cpuset.cpus.exclusive.effective is empty. B
should remain invalid until A can provide its exclusive CPUs again.
Shrinking A's exclusive CPUs invalidates B in
compute_partition_effective_cpumask(). The subsequent walk in
update_cpumasks_hier() tries to recover B, but
update_parent_effective_cpumask() skips the recovery checks when xcpus
is not a subset of parent->effective_xcpus. Since part_error is still
zero, B is changed back to a valid partition.
Set PERR_INVCPUS when the subset check fails so that the partition stays
invalid. New test cases are added to test_cpuset_prs.sh for removing and
restoring the parent's exclusive CPUs.
Fixes: 0c7f293efc87 ("cgroup/cpuset: Add cpuset.cpus.exclusive.effective for
v2")
Signed-off-by: Guopeng Zhang <[email protected]>
---
kernel/cgroup/cpuset.c | 8 ++++++--
tools/testing/selftests/cgroup/test_cpuset_prs.sh | 4 ++++
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 585a982249ad..be80763953ed 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1986,12 +1986,16 @@ static int update_parent_effective_cpumask(struct
cpuset *cs, int cmd,
cpumask_copy(tmp->addmask, cs->effective_xcpus);
adding = true;
}
- } else if (is_partition_invalid(cs) && !cpumask_empty(xcpus) &&
- cpumask_subset(xcpus, parent->effective_xcpus)) {
+ } else if (is_partition_invalid(cs) && !cpumask_empty(xcpus)) {
struct cgroup_subsys_state *css;
struct cpuset *child;
bool exclusive = true;
+ if (!cpumask_subset(xcpus, parent->effective_xcpus)) {
+ part_error = PERR_INVCPUS;
+ goto write_error;
+ }
+
/*
* Convert invalid partition to valid has to pass the
* cpu exclusivity test as well as the housekeeping
diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
index d04aad697b96..f1d517647ade 100755
--- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
+++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
@@ -427,6 +427,10 @@ TEST_MATRIX=(
# cpuset.cpus is allowed, but those extra CPUs are ignored.
" C2-3:P1 C3:P1 . . . C2-4 . . 0
A1:|A2:2-3 A1:P1|A2:P1"
+ # A child cannot recover until its exclusive CPUs are available again.
+ " CX1-4:P1 CX3-4:P1 . . X1-2 . . . 0
A1:1-2|A2:1-2|XA2: A1:P1|A2:P-1"
+ " CX1-4:P1 CX3-4:P1 . . X1-2:X1-4 . . . 0
A1:1-2|A2:3-4|XA2:3-4 A1:P1|A2:P1"
+
# Taking away all CPUs from parent or itself if there are tasks
# will make the partition invalid.
" C2-3:P1 C3:P1 . . T C2-3 . . 0
A1:2-3|A2:2-3 A1:P1|A2:P-1"
--
2.43.0
