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sched_ext: Defer sub_kset base put to scx_sched_free_rcu_work

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scx_sub_enable_workfn() pins parent->kobj before dropping scx_sched_lock,
but that does not pin parent->sub_kset. Concurrent disable can
kset_unregister and free sub_kset before scx_alloc_and_add_sched()
dereferences it.

Split sub_kset teardown: kobject_del() at disable keeps sysfs removal; defer
kobject_put() to scx_sched_free_rcu_work so the memory survives. A racing
child sees state_in_sysfs=0 with valid memory, sysfs_create_dir() fails, and
the existing exit_kind gate in scx_link_sched() turns it away with -ENOENT.

Fixes: 411d3ef1a7 ("sched_ext: Unregister sub_kset on scheduler disable")
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2026-05-11 13:18:23 -10:00
parent b273b75b8d
commit cceb874eee
1 changed files with 4 additions and 2 deletions
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6
kernel/sched/ext.c
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@ -4821,6 +4821,8 @@ static void scx_sched_free_rcu_work(struct work_struct *work)
kfree(sch->cgrp_path);
if (sch_cgroup(sch))
cgroup_put(sch_cgroup(sch));
if (sch->sub_kset)
kobject_put(&sch->sub_kset->kobj);
#endif /* CONFIG_EXT_SUB_SCHED */
for_each_possible_cpu(cpu) {
@ -5861,7 +5863,7 @@ static void scx_sub_disable(struct scx_sched *sch)
if (sch->ops.exit)
SCX_CALL_OP(sch, exit, NULL, sch->exit_info);
if (sch->sub_kset)
kset_unregister(sch->sub_kset);
kobject_del(&sch->sub_kset->kobj);
kobject_del(&sch->kobj);
}
#else /* CONFIG_EXT_SUB_SCHED */
@ -5995,7 +5997,7 @@ static void scx_root_disable(struct scx_sched *sch)
*/
#ifdef CONFIG_EXT_SUB_SCHED
if (sch->sub_kset)
kset_unregister(sch->sub_kset);
kobject_del(&sch->sub_kset->kobj);
#endif
kobject_del(&sch->kobj);