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75d8cce128
irq_poll_cpu_dead() pulls the blk_cpu_iopoll backlog from the dead CPU and raises the POLL softirq with __raise_softirq_irqoff() on the CPU it is running on. That just sets the bit in the pending softirq mask. This means the handling of the softirq is delayed until the next interrupt or a local_bh_disable/enable() pair. As a consequence the CPU on which this code runs can reach idle with the POLL softirq pending, which triggers a warning in the NOHZ idle code. Add a local_bh_disable/enable() pair around the interrupts disabled section in irq_poll_cpu_dead(). local_bh_enable will handle the pending softirq. [tglx: Massaged changelog and comment] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/87k0bxgl27.ffs@tglx
220 lines
5.6 KiB
C
220 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Functions related to interrupt-poll handling in the block layer. This
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* is similar to NAPI for network devices.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/bio.h>
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#include <linux/interrupt.h>
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#include <linux/cpu.h>
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#include <linux/irq_poll.h>
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#include <linux/delay.h>
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static unsigned int irq_poll_budget __read_mostly = 256;
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static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
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/**
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* irq_poll_sched - Schedule a run of the iopoll handler
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* @iop: The parent iopoll structure
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*
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* Description:
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* Add this irq_poll structure to the pending poll list and trigger the
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* raise of the blk iopoll softirq.
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**/
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void irq_poll_sched(struct irq_poll *iop)
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{
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unsigned long flags;
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if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
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return;
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if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
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return;
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local_irq_save(flags);
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list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
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raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL(irq_poll_sched);
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/**
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* __irq_poll_complete - Mark this @iop as un-polled again
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* @iop: The parent iopoll structure
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*
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* Description:
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* See irq_poll_complete(). This function must be called with interrupts
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* disabled.
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**/
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static void __irq_poll_complete(struct irq_poll *iop)
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{
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list_del(&iop->list);
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smp_mb__before_atomic();
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clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
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}
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/**
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* irq_poll_complete - Mark this @iop as un-polled again
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* @iop: The parent iopoll structure
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*
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* Description:
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* If a driver consumes less than the assigned budget in its run of the
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* iopoll handler, it'll end the polled mode by calling this function. The
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* iopoll handler will not be invoked again before irq_poll_sched()
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* is called.
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**/
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void irq_poll_complete(struct irq_poll *iop)
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{
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unsigned long flags;
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local_irq_save(flags);
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__irq_poll_complete(iop);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL(irq_poll_complete);
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static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
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{
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struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
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int rearm = 0, budget = irq_poll_budget;
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unsigned long start_time = jiffies;
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local_irq_disable();
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while (!list_empty(list)) {
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struct irq_poll *iop;
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int work, weight;
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/*
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* If softirq window is exhausted then punt.
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*/
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if (budget <= 0 || time_after(jiffies, start_time)) {
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rearm = 1;
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break;
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}
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local_irq_enable();
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/* Even though interrupts have been re-enabled, this
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* access is safe because interrupts can only add new
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* entries to the tail of this list, and only ->poll()
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* calls can remove this head entry from the list.
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*/
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iop = list_entry(list->next, struct irq_poll, list);
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weight = iop->weight;
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work = 0;
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if (test_bit(IRQ_POLL_F_SCHED, &iop->state))
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work = iop->poll(iop, weight);
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budget -= work;
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local_irq_disable();
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/*
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* Drivers must not modify the iopoll state, if they
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* consume their assigned weight (or more, some drivers can't
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* easily just stop processing, they have to complete an
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* entire mask of commands).In such cases this code
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* still "owns" the iopoll instance and therefore can
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* move the instance around on the list at-will.
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*/
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if (work >= weight) {
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if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
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__irq_poll_complete(iop);
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else
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list_move_tail(&iop->list, list);
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}
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}
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if (rearm)
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__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
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local_irq_enable();
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}
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/**
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* irq_poll_disable - Disable iopoll on this @iop
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* @iop: The parent iopoll structure
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*
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* Description:
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* Disable io polling and wait for any pending callbacks to have completed.
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**/
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void irq_poll_disable(struct irq_poll *iop)
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{
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set_bit(IRQ_POLL_F_DISABLE, &iop->state);
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while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
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msleep(1);
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clear_bit(IRQ_POLL_F_DISABLE, &iop->state);
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}
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EXPORT_SYMBOL(irq_poll_disable);
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/**
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* irq_poll_enable - Enable iopoll on this @iop
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* @iop: The parent iopoll structure
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*
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* Description:
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* Enable iopoll on this @iop. Note that the handler run will not be
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* scheduled, it will only mark it as active.
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**/
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void irq_poll_enable(struct irq_poll *iop)
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{
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BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));
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smp_mb__before_atomic();
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clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
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}
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EXPORT_SYMBOL(irq_poll_enable);
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/**
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* irq_poll_init - Initialize this @iop
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* @iop: The parent iopoll structure
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* @weight: The default weight (or command completion budget)
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* @poll_fn: The handler to invoke
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*
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* Description:
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* Initialize and enable this irq_poll structure.
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**/
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void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)
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{
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memset(iop, 0, sizeof(*iop));
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INIT_LIST_HEAD(&iop->list);
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iop->weight = weight;
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iop->poll = poll_fn;
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}
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EXPORT_SYMBOL(irq_poll_init);
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static int irq_poll_cpu_dead(unsigned int cpu)
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{
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/*
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* If a CPU goes away, splice its entries to the current CPU and
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* set the POLL softirq bit. The local_bh_disable()/enable() pair
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* ensures that it is handled. Otherwise the current CPU could
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* reach idle with the POLL softirq pending.
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*/
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local_bh_disable();
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local_irq_disable();
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list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
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this_cpu_ptr(&blk_cpu_iopoll));
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__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
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local_irq_enable();
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local_bh_enable();
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return 0;
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}
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static __init int irq_poll_setup(void)
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{
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int i;
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for_each_possible_cpu(i)
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INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
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open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq);
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cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL,
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irq_poll_cpu_dead);
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return 0;
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}
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subsys_initcall(irq_poll_setup);
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