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sched_ext: Require cid-form struct_ops for sub-sched support

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Sub-scheduler support is tied to the cid-form struct_ops: sub_attach /
sub_detach will communicate allocation via cmask, and the hierarchy assumes
all participants share a single topological cid space. A cpu-form root that
accepts sub-scheds would need cpu <-> cid translation on every cross-sched
interaction, defeating the purpose.

Enforce this at validate_ops():
- A sub-scheduler (scx_parent(sch) non-NULL) must be cid-form.
- A root that exposes sub_attach / sub_detach must be cid-form.

scx_qmap, which is currently the only scheduler demoing sub-sched support,
was converted to cid-form in the preceding patch, so this doesn't cause
breakage.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Reviewed-by: Changwoo Min <changwoo@igalia.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
This commit is contained in:
Tejun Heo 2026-04-29 08:09:11 -10:00
parent 5ea59a3af5
commit 97f86c38ab
1 changed files with 17 additions and 0 deletions
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17
kernel/sched/ext.c
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@ -6869,6 +6869,23 @@ static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
if (!sch->is_cid_type && (ops->cpu_acquire || ops->cpu_release))
pr_warn("ops->cpu_acquire/release() are deprecated, use sched_switch TP instead\n");
/*
* Sub-scheduler support is tied to the cid-form struct_ops. A sub-sched
* attaches through a cid-form-only interface (sub_attach/sub_detach),
* and a root that accepts sub-scheds must expose cid-form state to
* them. Reject cpu-form schedulers on either side.
*/
if (!sch->is_cid_type) {
if (scx_parent(sch)) {
scx_error(sch, "sub-sched requires cid-form struct_ops");
return -EINVAL;
}
if (ops->sub_attach || ops->sub_detach) {
scx_error(sch, "sub_attach/sub_detach requires cid-form struct_ops");
return -EINVAL;
}
}
return 0;
}