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cgroup/cpuset: Use WRITE_ONCE() for shared prs_err updates

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cpuset_partition_show() reads cs->prs_err without cpuset_mutex using
READ_ONCE(). The field is documented as not lock protected, but several
updates to live cpusets still use plain stores.

Convert the remaining prs_err stores on live cpusets to WRITE_ONCE().

Fixes: 0c7f293efc ("cgroup/cpuset: Add cpuset.cpus.exclusive.effective for v2")
Assisted-by: LLM
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Guopeng Zhang 2026-08-10 17:55:59 +08:00 committed by Tejun Heo
parent 77bc7e952f
commit 26d3a59e02
1 changed files with 13 additions and 11 deletions
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24
kernel/cgroup/cpuset.c
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@ -1587,7 +1587,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
cpumask_copy(cs->effective_xcpus, tmp->new_cpus);
spin_unlock_irq(&callback_lock);
cpuset_force_rebuild();
cs->prs_err = 0;
WRITE_ONCE(cs->prs_err, 0);
/*
* Propagate changes in top_cpuset's effective_cpus down the hierarchy.
@ -1661,7 +1661,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));
if (cpumask_empty(excpus)) {
cs->prs_err = PERR_CPUSEMPTY;
WRITE_ONCE(cs->prs_err, PERR_CPUSEMPTY);
goto invalidate;
}
@ -1676,13 +1676,13 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
if (adding) {
WARN_ON_ONCE(cpumask_intersects(tmp->addmask, subpartitions_cpus));
if (!capable(CAP_SYS_ADMIN))
cs->prs_err = PERR_ACCESS;
WRITE_ONCE(cs->prs_err, PERR_ACCESS);
else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
cpumask_subset(top_cpuset.effective_cpus, tmp->addmask))
cs->prs_err = PERR_NOCPUS;
WRITE_ONCE(cs->prs_err, PERR_NOCPUS);
else if ((prs == PRS_ISOLATED) &&
!isolated_cpus_can_update(tmp->addmask, tmp->delmask))
cs->prs_err = PERR_HKEEPING;
WRITE_ONCE(cs->prs_err, PERR_HKEEPING);
if (cs->prs_err)
goto invalidate;
}
@ -2110,13 +2110,13 @@ static void compute_partition_effective_cpumask(struct cpuset *cs,
* partition root.
*/
WARN_ON_ONCE(is_remote_partition(child));
child->prs_err = 0;
WRITE_ONCE(child->prs_err, 0);
if (!cpumask_subset(child->effective_xcpus,
cs->effective_xcpus))
child->prs_err = PERR_INVCPUS;
WRITE_ONCE(child->prs_err, PERR_INVCPUS);
else if (populated &&
cpumask_subset(new_ecpus, child->effective_xcpus))
child->prs_err = PERR_NOCPUS;
WRITE_ONCE(child->prs_err, PERR_NOCPUS);
if (child->prs_err) {
int old_prs = child->partition_root_state;
@ -2420,8 +2420,10 @@ static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs,
return;
prs_err = validate_partition(cs, trialcs);
if (prs_err)
trialcs->prs_err = cs->prs_err = prs_err;
if (prs_err) {
WRITE_ONCE(cs->prs_err, prs_err);
trialcs->prs_err = prs_err;
}
if (is_remote_partition(cs)) {
if (trialcs->prs_err)
@ -3939,7 +3941,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
if (remote && (cpumask_empty(subpartitions_cpus) ||
(cpumask_empty(&new_cpus) &&
partition_is_populated(cs, NULL)))) {
cs->prs_err = PERR_HOTPLUG;
WRITE_ONCE(cs->prs_err, PERR_HOTPLUG);
remote_partition_disable(cs, tmp);
compute_effective_cpumask(&new_cpus, cs, parent);
remote = false;