cpuhp_invoke_callback(9)

💅 cpuhp_invoke_callback — like, the whole kernel API manual moment ✨

okay so bestie, buckle up, because this page is literally from the Kernel API Manual and it's about firing off callbacks for a CPU hotplug state. it's giving "behind the scenes of the kernel" energy and honestly? iconic. 🎀

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✨ SYNOPSIS ✨

int cpuhp_invoke_callback (unsigned int cpu , enum cpuhp_state state ,
       bool bringup , struct hlist_node *node , struct hlist_node **lastp );

no cap, that's the whole signature. five args, one int coming back at you. 🫶

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🌸 ARGUMENTS 🌸

• cpu — the cpu like, the actual one 👑 — the CPU for which the callback should be invoked. that's the vibe check target, bestie.
• state — the state to do callbacks for. yes, an enum cpuhp_state. yes, it matters. 🙈
• bringup — a bool, and it's True if the bringup callback should be invoked. so like, are we bringing it up or not, that is the question 💀
• node — for multi-instance, do a single entry callback for install/remove. so it's a struct hlist_node * and it's the one-entry girlie for install/remove situations ✨
• lastp — for multi-instance rollback, remember how far we got. a struct hlist_node ** that's basically the "wait, where were we" bookmark 🎀

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🦋 DESCRIPTION 🦋

Called from cpu hotplug and from the state register machinery.

that's it. that's the description. she's short, she's mysterious, she's lowkey the main character of ./kernel/cpu.c. periodt. 💅

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⭐ RETURN ⭐

0 on success, or a negative errno code. that's the whole mood. slay. 🔥

ok real talk: negative errno means something went sideways, so like… check it, bestie. don't just vibe past the return value. 😭

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🌈 SEE ALSO 🌈

• kernel file ./kernel/cpu.c
• struct cpuhp_cpu_state(9)
• struct cpuhp_step(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_setup_state_cpuslocked(9)
• __cpuhp_remove_state_cpuslocked(9)

like, read them all, they're all connected, iykyk 💜

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and that's the page! 🧚 from ./kernel, dated October 2026, and this was cpuhp_invoke_callback(9) — go forth and invoke those callbacks responsibly, bestie, mwah 💖🍓