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sched_ext: Unregister sub_kset on scheduler disable

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When ops.sub_attach is set, scx_alloc_and_add_sched() creates sub_kset as a
child of &sch->kobj, which pins the parent with its own reference. The
disable paths never call kset_unregister(), so the final kobject_put() in
bpf_scx_unreg() leaves a stale reference and scx_kobj_release() never runs,
leaking the whole struct scx_sched on every load/unload cycle.

Unregister sub_kset in scx_root_disable() and scx_sub_disable() before
kobject_del(&sch->kobj).

Fixes: ebeca1f930 ("sched_ext: Introduce cgroup sub-sched support")
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2026-04-24 14:31:35 -10:00
parent bd2d76455b
commit 411d3ef1a7
1 changed files with 6 additions and 0 deletions
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6
kernel/sched/ext.c
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@ -5721,6 +5721,8 @@ static void scx_sub_disable(struct scx_sched *sch)
if (sch->ops.exit) if (sch->ops.exit)
SCX_CALL_OP(sch, exit, NULL, sch->exit_info); SCX_CALL_OP(sch, exit, NULL, sch->exit_info);
if (sch->sub_kset)
kset_unregister(sch->sub_kset);
kobject_del(&sch->kobj); kobject_del(&sch->kobj);
} }
#else /* CONFIG_EXT_SUB_SCHED */ #else /* CONFIG_EXT_SUB_SCHED */
@ -5852,6 +5854,10 @@ static void scx_root_disable(struct scx_sched *sch)
* could observe an object of the same name still in the hierarchy when * could observe an object of the same name still in the hierarchy when
* the next scheduler is loaded. * the next scheduler is loaded.
*/ */
#ifdef CONFIG_EXT_SUB_SCHED
if (sch->sub_kset)
kset_unregister(sch->sub_kset);
#endif
kobject_del(&sch->kobj); kobject_del(&sch->kobj);
free_kick_syncs(); free_kick_syncs();