__cpuhp_setu...e_cpuslocked(9)

💖 __cpuhp_setup_state_cpuslocked(9) 💖

okay so bestie, welcome to the Kernel API Manual ✨ this one's a whole function, and honestly? she's kind of a big deal. let's get into it 🫶

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🌸 NAME 🌸

__cpuhp_setup_state_cpuslocked — set up the callbacks for a hotplug machine state 🎀

like, you're literally wiring up what happens when a CPU joins or leaves the party 💅

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✨ SYNOPSIS ✨

int __cpuhp_setup_state_cpuslocked (enum cpuhp_state state , const char
*name , bool invoke , int (*startup)(unsigned int cpu) , int
(*teardown)(unsigned int cpu) , bool multi_instance );

she takes six arguments and returns an int, no cap 🔥

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🦋 ARGUMENTS 🦋

• state — the state you're setting up. that's the whole vibe check of this call 👑
• name — the name of the step. give her a cute label fr 💖
• invoke — if this is true, the startup function gets invoked for cpus where cpu state is >= state. yes, greater-than-or-equal, don't @ me 😭
• startup — the startup callback function. signature is int (*startup)(unsigned int cpu) ✨
• teardown — the teardown callback function. signature is int (*teardown)(unsigned int cpu) 🎀
• multi_instance — state is set up for multiple instances which get added afterwards. so like, more than one, added later, iykyk 🦋

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💅 DESCRIPTION 💅

the caller needs to hold cpus read locked while calling this function.

bestie. please. read lock. hold it. this is not optional 🙈

that's literally the whole description and honestly it's giving "short but load-bearing" 💀

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🌈 RETURN 🌈

on success:

• a positive state number if state is CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN ⭐
• 0 for all other states 👑

on failure:

• the proper (negative) error code 😭

so like, check your return value, always 💜

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🍓 SEE ALSO 🍓

• Kernel file ./kernel/cpu.c
• struct cpuhp_cpu_state(9)
• struct cpuhp_step(9)
• cpuhp_invoke_callback(9)
• cpuhp_ap_update_sync_state(9)
• cpuhp_ap_report_dead(9)
• cpuhp_ap_sync_alive(9)
• clear_tasks_mm_cpumask(9)
• cpu_device_down(9)
• notify_cpu_starting(9)
• cpu_device_up(9)
• bringup_hibernate_cpu(9)
• __cpuhp_remove_state_cpuslocked(9)

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okay that's the whole page, go read the source bestie 🧚💖

sign-off time: this iconic lil page lives in ./kernel, dated October 2026, and the manual name is literally __cpuhp_setu...e_cpuslocked(9) — yes the title's truncated, she's mysterious like that 💅✨