idle_cpu(9)

💤 idle_cpu(9) — like, is this CPU chilling rn?

ok so this is a page from the Kernel API Manual, and it's about idle_cpu ... which, bestie, is the most "no thoughts head empty" question you can ask the scheduler: is this CPU literally doing nothing right now? 🦋

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✨ NAME ✨

idle_cpu — is a given CPU idle currently?

Like, present tense. Currently. It's a vibe check for a processor. 💅

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🎀 SYNOPSIS 🎀

int idle_cpu (int cpu );

Yup that's it. One arg, one int back. Iconic minimalism, no cap. ✨

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🌸 ARGUMENTS 🌸

• cpu — the processor in question. The one you're side-eyeing. The one whose whole situation you want the tea on. 👀

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⭐ RETURN ⭐

• 1 — if the CPU is currently idle. She's free. She's available. She's not doing anything rn. 😴
• 0 — otherwise. She's busy, she's booked, she's got a runqueue to worry about. 💀

That's the whole return contract, fr fr — just 1 or 0, no fancy negative-errno drama here.

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🔥 SEE ALSO 🔥

Also check out the Kernel file ./kernel/sched/syscalls.c, plus all these sibling pages if you wanna go down the scheduling rabbit hole (iykyk):

• task_prio(9)
• idle_task(9)
• find_process_by_pid(9)
• sched_setscheduler(9)
• sched_setscheduler_nocheck(9)
• sys_sched_setscheduler(9)
• sys_sched_setparam(9)
• sys_sched_setattr(9)
• sys_sched_getscheduler(9)
• sys_sched_getparam(9)
• sys_sched_getattr(9)
• sys_sched_setaffinity(9)
• sys_sched_getaffinity(9)
• sys_sched_yield(9)
• yield(9)
• yield_to(9)
• sys_sched_get_priority_max(9)
• sys_sched_get_priority_min(9)
• sys_sched_rr_get_interval(9)

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💖 tiny note: this page lives in ./kernel/sched — that's her home, that's her whole address.

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ok that's the whole page, you ate that 🫶 this cutie dropped in October 2026, filed under ./kernel/sched, and she answers to the name idle_cpu(9) — go forth and check your CPUs, bestie 🌈👑