synchronize_irq(9)

💖 synchronize_irq(9) 💖

okay bestie, welcome to the Kernel API Manual — this is the group-chat explainer for one very specific “wait for the interrupt handlers to finish” moment, and it’s giving main character energy. 🦋✨

✨ NAME ✨

synchronize_irq — wait for pending IRQ handlers (on other CPUs)

🌸 SYNOPSIS 🌸

void synchronize_irq (unsigned int irq );

🎀 ARGUMENTS 🎀

• irq — interrupt number to wait for.

💅 DESCRIPTION 💅

okay so here’s the vibe: this function waits for any pending IRQ handlers for this interrupt to complete before returning. periodt. It is literally not returning until those handlers are done. 🫶

🚨 deadlock warning, bestie: if you use this function while holding a resource the IRQ handler may need, you will deadlock. no cap. do not do that. 💀

It can only be called from preemptible code, because it might sleep when an interrupt thread is associated to irq. 😴

It optionally makes sure — when the irq chip supports that method — that the interrupt is not pending in any CPU and waiting for service. highkey thorough, ngl. ✨

🦋 SEE ALSO 🦋

Kernel file ./kernel/irq/manage.c — synchronize_hardirq(9), irq_can_set_affinity(9), irq_can_set_affinity_usr(9), irq_set_thread_affinity(9), irq_affinity_schedule_notify_work(9), irq_update_affinity_desc(9), irq_set_affinity(9), irq_force_affinity(9), irq_set_affinity_notifier(9), irq_set_vcpu_affinity(9), disable_irq_nosync(9), disable_irq(9), disable_hardirq(9), disable_nmi_nosync(9), enable_irq(9), enable_nmi(9), irq_set_irq_wake(9), irq_wake_thread(9), free_irq(9), request_threaded_irq(9), request_any_context_irq(9), request_nmi(9), irq_percpu_is_enabled(9), free_percpu_irq(9), request_percpu_irq_affinity(9), request_percpu_nmi(9), prepare_percpu_nmi(9), teardown_percpu_nmi(9), irq_get_irqchip_state(9), irq_set_irqchip_state(9), irq_has_action(9), irq_check_status_bit(9)

mwah 💋 that’s the whole page, bestie — signed off from the source/version ./kernel/irq, dated October 2026, and it’s all about synchronize_irq(9). 🫶🌈