cid_valid(9)

✨ cid_valid(9) ✨

okay so bestie, welcome to the cid_valid(9) page — that's the kernel API manual, and yes we're gonna read it together, it's short and it's iconic 💅

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🎀 NAME 🎀

cid_valid — verify a cid value, to be used on ops input args. that's literally the whole job description and she does it well 🫶

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🌸 SYNOPSIS 🌸

bool cid_valid (struct scx_sched *sch , s32 cid );

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💖 ARGUMENTS 💖

• sch — the scx_sched that gets aborted on error 😭 like, if things go bad, this is the one catching the fallout.
• cid — the cid which came from a BPF ops ✨ it's giving "value from the outside world", so of course we gotta check it.

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🦋 DESCRIPTION 🦋

so here's the tea ☕ — this function returns true if cid is in [0, num_possible_cpus) 👑 that's the sweet spot, that's the range, that's where we want her to be.

on failure? it triggers scx_error and returns false 💀 no cap, that's the whole flow. validate, and if it doesn't vibe check out, error out and say no.

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🌈 SEE ALSO 🌈

kernel file ./kernel/sched/ext/cid.h — and the whole friend group:

• __scx_cid_to_cpu(9)
• __scx_cpu_to_cid(9)
• scx_cid_to_cpu(9)
• scx_cpu_to_cid(9)
• scx_is_cid_type(9)
• __scx_cmask_init(9)
• scx_cmask_init(9)
• scx_cmask_reframe(9)
• scx_cmask_test(9)
• scx_cmask_for_each_cid(9)

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ngl bestie, if you're out here passing a cid from a BPF ops without checking it first, this page is your sign 🫶 use the validator, protect your scheduler, periodt 💜

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and that's the page!! sign-off time 🎀 this one lives in ./kernel/sched/ext, dated October 2026 — mwah, go forth and validate responsibly, iykyk 🧚💖