scx_bpf_sub_caps(9)

💅 scx_bpf_sub_caps(9)

ok so bestie, welcome to the Kernel API Manual ✨ — this page is literally about reading cap cmasks for yourself or your direct child, and honestly it's giving "small function, big feelings". Let's get into it 🫶

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🌸 NAME 🌸

scx_bpf_sub_caps — read self's or a direct child's cap cmasks 💖

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✨ SYNOPSIS ✨

__bpf_kfunc s32 scx_bpf_sub_caps (u64 cgroup_id , u64 caps , struct
scx_cmask *out__arena , const struct bpf_prog_aux *aux );

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🎀 ARGUMENTS 🎀

• cgroup_id — pass 0 for self, or hand over a direct child's cgroup id. that's the whole vibe ✨
• caps — one or more SCX_CAP_* bits. yes, more than one, go off king 👑
• out__arena — the cmask that receives the union of caps within its range. it's the little bucket your answer drops into 🪣💜
• aux — implicit BPF argument. not me having to explain this every time 🙈 it's just there, bestie.

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💅 DESCRIPTION 💅

So what does it actually do? It reads the cap cmasks granted on each cid — for self when cgroup_id is 0, or for a direct child otherwise. it's the literal granted set, no cap, fr fr 💀

and there's a boundary, okay? a sched can read only itself or a direct child. that's the rule, periodt. 🚧

Return values, because iykyk:

• 0 — slay, it worked ⭐
• -ENODEV — cgroup_id names no direct child, so like… who even is she 😭
• -EINVAL — bad inputs. check ur args bestie 🍓

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🦋 SEE ALSO 🦋

the whole friend group 💜 — Kernel file ./kernel/sched/ext/sub.c and literally all of these:

• scx_skip_subtree_pre(9)
• scx_next_descendant_pre(9)
• scx_rescue_charge(9)
• scx_rescue_end(9)
• scx_rescue_keep(9)
• scx_rescue_accrue(9)
• scx_rescue_admit(9)
• scx_rescue_try_admit(9)
• scx_rescue_check_overload(9)
• scx_rescue_timerfn(9)
• scx_resolve_local_dsq(9)
• queue_sync_ecaps(9)
• scx_process_sync_ecaps(9)
• scx_unbypass_replay_ecaps(9)
• scx_discard_stale_ecaps_syncs(9)
• scx_rehome_task(9)
• scx_punt_task(9)
• scx_cgroup_claim_subtree(9)
• scx_cgroup_return_subtree(9)
• scx_cgroup_task_migrating(9)
• scx_cgroup_task_migrated(9)
• scx_cgroup_task_migrate_canceled(9)
• scx_bpf_sub_dispatch(9)
• scx_bpf_sub_grant(9)
• scx_bpf_sub_revoke(9)
• scx_bpf_sub_kill_bstr(9)

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and that's the whole page bestie 🌈✨ this one's straight outta ./kernel/sched/ext, dated October 2026 — go forth and read those cmasks, icon 💅👑🎀