scx_cmask_test(9)

💅 scx_cmask_test(9) — Kernel API Manual, bestie edition

okay so we’re looking at scx_cmask_test(9), and honestly? It’s giving “tiny function, very important vibe check.” Let’s get into it 🫶

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✨ NAME ✨

scx_cmask_test — test whether @cid is set in @m

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🦋 SYNOPSIS 🦋

bool scx_cmask_test (u32 cid , const struct scx_cmask *m );

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🎀 ARGUMENTS 🎀

• cid — the cid to test, bestie. That’s the one we’re checking on.
• m — the cmask to test. This is the mask getting inspected.

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🔥 DESCRIPTION 🔥

So here’s the tea: if cid is outside m’s active range, this returns false. Periodt.

Otherwise, it returns the bit’s value. Yep, that’s the whole main character moment.

And important detail, no cap: the read happens via READ_ONCE, so callers can race set/clear writers. Read that again if you need to — it’s literally right there in the function’s whole deal 💅

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🌈 SEE ALSO 🌈

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

• cid_valid(9)
• __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_for_each_cid(9)

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xoxo, signing off from ./kernel/sched/ext — October 2026 — scx_cmask_test(9) 💖✨