cpuhp_ap_update_sync_state(9)

💅 cpuhp_ap_update_sync_state — like, the kernel API manual bestie ✨

okay so this is a page from the Kernel API Manual (yes, section 9, the fancy "kernel internals" section, iykyk) and it's about one very specific little function. it's short. it's sweet. it's giving "tiny function, huge responsibility." let's get into it 🫶

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✨ NAME ✨

cpuhp_ap_update_sync_state — literally just updates the synchronization state during bringup/teardown. that's the whole job. no cap.

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🦋 SYNOPSIS 🦋

void cpuhp_ap_update_sync_state (enum cpuhp_sync_state state );

yes bestie, it returns void. it does the thing and dips. 💅

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🎀 ARGUMENTS 🎀

• state — the synchronization state you wanna set. that's it. it's an enum cpuhp_sync_state and it's the synchronisation state to set. very demure, very mindful. 🌸

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👑 DESCRIPTION 👑

okay so important vibe check here: there is no synchronization point in this function. like, zero. it does not stop and wait for anyone. it's just a straight-up update of the synchronization state. 🧚

but (and this is the main character detail) it implies a full barrier, so the AP changes are visible before the control CPU proceeds. it's not a fancy handshake, it's a "hey, everything you need to see is visible now, go ahead" — and the control CPU can carry on knowing the AP-side changes made it through. 🔥

fr fr though, don't go expecting this to synchronize anything for you. it updates state, it gives you the barrier, it moves on. the synchronization point? not here. periodt. 💀

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🌈 SEE ALSO 🌈

go touch some of these next, bestie:

• Kernel file ./kernel/cpu.c
• struct cpuhp_cpu_state(9)
• struct cpuhp_step(9)
• cpuhp_invoke_callback(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)

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and that's the whole page, bestie, you ate it up 💖 it lives over in ./kernel, and this particular printing is dated October 2026 — so mark your calendar, star the page, and remember: cpuhp_ap_update_sync_state(9), the tiny barrier-giving icon that it is. slay. 🎀⭐