STRUCT CPUHP_CPU_STATE(9)

💅 struct cpuhp_cpu_state(9)

okay so bestie, this page comes from the Kernel API Manual (section 9, the kernel-internals girlies) and it's literally all about struct cpuhp_cpu_state — the per-CPU hotplug state storage. it's giving "where a CPU keeps its own little diary of what state it's in." no cap.

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✨ NAME ✨

struct cpuhp_cpu_state — per cpu hotplug state storage 🫶

like, per CPU. each one gets their own. main character energy for every core.

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🌸 SYNOPSIS 🌸

here's the whole vibe, exactly as it is, don't @ me:

struct cpuhp_cpu_state {
    enum cpuhp_state        state;
    enum cpuhp_state        target;
    enum cpuhp_state        fail;
  #ifdef CONFIG_SMP;
    struct task_struct      *thread;
    bool should_run;
    bool rollback;
    bool single;
    bool bringup;
    struct hlist_node       *node;
    struct hlist_node       *last;
    enum cpuhp_state        cb_state;
    int result;
    atomic_t ap_sync_state;
    struct completion       done_up;
    struct completion       done_down;
  #endif;
 };

🚨 bestie look at that #ifdef CONFIG_SMP; — everything below it only exists when CONFIG_SMP is set. no SMP, no thread field, no completions, nothing. she said "not today."

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🎀 Members 🎀

like a group photo, one by one, no one left out:

• state — the current cpu state. where she's at right now 💁‍♀️
• target — the target state. where she's trying to go. the goal. the vision board.
• fail — current CPU hotplug callback state. (yes it's named fail, she's just built different 🥲)
• thread — pointer to the hotplug thread. the one doing the actual work, honestly iconic.
• should_run — thread should execute. a whole bool just to say "go bestie."
• rollback — perform a rollback. we're taking it back, no shame.
• single — single callback invocation. just one. a little solo moment.
• bringup — single callback bringup or teardown selector. which direction are we going, up or down? selector energy.
• node — remote CPU node; for multi-instance, do a single entry callback for install/remove.
• last — for multi-instance rollback, remember how far we got. the receipts 📝
• cb_state — the state for a single callback (install/uninstall).
• result — result of the operation. did we slay or did we flop, that's the whole field.
• ap_sync_state — state for AP synchronization.
• done_up — signal completion to the issuer of the task for cpu-up. ⬆️ done!
• done_down — signal completion to the issuer of the task for cpu-down. ⬇️ done!

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🦋 SEE ALSO 🦋

the whole friend group, in ./kernel/cpu.c:

• 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_setup_state_cpuslocked(9)
• __cpuhp_remove_state_cpuslocked(9)

iykyk 💜

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and that's the page!! sourced straight from ./kernel, dated October 2026 ⭐ — go off, kernel girlies, this one's for you 🧚💖