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cgroup/cpuset: Release invalid isolated CPUs in compute_partition_effective_cpumask()

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It is found by sashiko that when a child isolated partition with parent
root partition is invalidated in compute_partition_effective_cpumask(),
the switching of the isolated exclusive CPUs from child to parent will
not be reflected in isolated_cpus leading to CPU leakage. Fix that by
calling isolated_cpus_update() when that happens.

Also simplify compute_partition_effective_cpumask() by doing
child partition invalidation only for the special case of no more
effective_cpus left in a populated parent. The other case doesn't
actually warrant invalidation at this stage and subsequent iteration
in update_cpumasks_hier() and update_parent_effective_cpumask() for
that child should handle that.

Also drop the make_partition_invalid() helper by inlining it into
compute_partition_effective_cpumask() as it is the only caller.

A new test case is add to test_cpuset_prs.sh to verify this.

Fixes: 11e5f407b6 ("cgroup/cpuset: Keep track of CPUs in isolated partitions")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Tested-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2026-10-25 17:44:46 -04:00 committed by Tejun Heo
parent 356a3aa740
commit a7d89d92fd
2 changed files with 21 additions and 29 deletions
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46
kernel/cgroup/cpuset.c
View File

@ -254,15 +254,6 @@ static inline bool cs_is_member(const struct cpuset *cs)
return cs->partition_root_state == PRS_MEMBER;
}
/*
* Callers should hold callback_lock to modify partition_root_state.
*/
static inline void make_partition_invalid(struct cpuset *cs)
{
if (cs->partition_root_state > 0)
cs->partition_root_state = -cs->partition_root_state;
}
/*
* Send notification event of whenever partition_root_state changes.
*/
@ -2153,8 +2144,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
* or update_cpumasks_hier() where parent and children are modified
* successively, we don't need to call update_parent_effective_cpumask()
* and the child's effective_cpus will be updated in later iterations.
*
* Note that rcu_read_lock() is assumed to be held.
*/
static void compute_partition_effective_cpumask(struct cpuset *cs,
struct cpumask *new_ecpus)
@ -2166,15 +2155,16 @@ static void compute_partition_effective_cpumask(struct cpuset *cs,
WARN_ON_ONCE(!is_partition_valid(cs));
/*
* Check child partition roots to see if they should be
* invalidated when
* 1) child effective_xcpus not a subset of new
* excluisve_cpus
* 2) All the effective_cpus will be used up and cp
* has tasks
* Check child partition roots to see if they should be invalidated
* when all the effective_cpus will be used up and cs is populated.
* It is better to sacrifice a child partition root than invalidating
* the whole subtree.
*
* Return early if the effective_cpus is already empty.
*/
compute_excpus(cs, new_ecpus);
cpumask_and(new_ecpus, new_ecpus, cpu_active_mask);
if (!cpumask_and(new_ecpus, new_ecpus, cpu_active_mask))
return;
rcu_read_lock();
cpuset_for_each_child(child, css, cs) {
@ -2186,22 +2176,20 @@ static void compute_partition_effective_cpumask(struct cpuset *cs,
* partition root.
*/
WARN_ON_ONCE(is_remote_partition(child));
WRITE_ONCE(child->prs_err, 0);
if (!cpumask_subset(child->effective_xcpus,
cs->effective_xcpus))
WRITE_ONCE(child->prs_err, PERR_INVCPUS);
else if (populated &&
cpumask_subset(new_ecpus, child->effective_xcpus))
WRITE_ONCE(child->prs_err, PERR_NOCPUS);
if (child->prs_err) {
if (populated && cpumask_subset(new_ecpus, child->effective_xcpus)) {
int old_prs = child->partition_root_state;
int parent_prs = cs->partition_root_state;
/*
* Invalidate child partition
* Invalidate child partition and update isolated_cpus
* if necessary.
*/
spin_lock_irq(&callback_lock);
make_partition_invalid(child);
WRITE_ONCE(child->prs_err, PERR_NOCPUS);
if ((old_prs == PRS_ISOLATED) && (parent_prs == PRS_ROOT))
isolated_cpus_update(PRS_ISOLATED, PRS_ROOT,
child->effective_xcpus);
child->partition_root_state = -old_prs;
spin_unlock_irq(&callback_lock);
notify_partition_change(child, old_prs);
continue;

4
tools/testing/selftests/cgroup/test_cpuset_prs.sh
View File

@ -521,6 +521,10 @@ TEST_MATRIX=(
" CX0-4:P2 CX2-4:P2 CX3-4:P2 . . X2 . . 0 A1:0-1,3-4|A2:2|A3:2 \
A1:P2|A2:P2|A3:P-2 0-4"
# When an isolated partition child with root partition parent is invalidated,
# its effective xcpus will be removed from isolated_cpus.
" C1-4:P1 C3-4:P2 . . T:C3-4 . . . 0 A1:3-4|A2:3-4 A1:P1|A2:P-2 ."
#
# old-A1 old-A2 old-A3 old-B1 new-A1 new-A2 new-A3 new-B1 fail ECPUs Pstate ISOLCPUS
# ------ ------ ------ ------ ------ ------ ------ ------ ---- ----- ------ --------