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![Linus Torvalds](/assets/img/avatar_default.png)
Pull core locking updates from Ingo Molnar: "The main changes in this cycle were: - reduced/streamlined smp_mb__*() interface that allows more usecases and makes the existing ones less buggy, especially in rarer architectures - add rwsem implementation comments - bump up lockdep limits" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits) rwsem: Add comments to explain the meaning of the rwsem's count field lockdep: Increase static allocations arch: Mass conversion of smp_mb__*() arch,doc: Convert smp_mb__*() arch,xtensa: Convert smp_mb__*() arch,x86: Convert smp_mb__*() arch,tile: Convert smp_mb__*() arch,sparc: Convert smp_mb__*() arch,sh: Convert smp_mb__*() arch,score: Convert smp_mb__*() arch,s390: Convert smp_mb__*() arch,powerpc: Convert smp_mb__*() arch,parisc: Convert smp_mb__*() arch,openrisc: Convert smp_mb__*() arch,mn10300: Convert smp_mb__*() arch,mips: Convert smp_mb__*() arch,metag: Convert smp_mb__*() arch,m68k: Convert smp_mb__*() arch,m32r: Convert smp_mb__*() arch,ia64: Convert smp_mb__*() ...
224 lines
5.8 KiB
C
224 lines
5.8 KiB
C
/*
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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/blkdev.h>
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#include <linux/interrupt.h>
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#include <linux/cpu.h>
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#include <linux/blk-iopoll.h>
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#include <linux/delay.h>
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#include "blk.h"
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static unsigned int blk_iopoll_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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* blk_iopoll_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 blk_iopoll structure to the pending poll list and trigger the
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* raise of the blk iopoll softirq. The driver must already have gotten a
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* successful return from blk_iopoll_sched_prep() before calling this.
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**/
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void blk_iopoll_sched(struct blk_iopoll *iop)
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{
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unsigned long flags;
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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(BLOCK_IOPOLL_SOFTIRQ);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL(blk_iopoll_sched);
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/**
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* __blk_iopoll_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 blk_iopoll_complete(). This function must be called with interrupts
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* disabled.
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**/
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void __blk_iopoll_complete(struct blk_iopoll *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(IOPOLL_F_SCHED, &iop->state);
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}
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EXPORT_SYMBOL(__blk_iopoll_complete);
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/**
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* blk_iopoll_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 blk_iopoll_sched_prep()
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* is called.
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**/
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void blk_iopoll_complete(struct blk_iopoll *iop)
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{
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unsigned long flags;
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local_irq_save(flags);
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__blk_iopoll_complete(iop);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL(blk_iopoll_complete);
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static void blk_iopoll_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 = blk_iopoll_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 blk_iopoll *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 blk_iopoll, list);
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weight = iop->weight;
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work = 0;
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if (test_bit(IOPOLL_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 (blk_iopoll_disable_pending(iop))
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__blk_iopoll_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(BLOCK_IOPOLL_SOFTIRQ);
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local_irq_enable();
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}
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/**
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* blk_iopoll_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 blk_iopoll_disable(struct blk_iopoll *iop)
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{
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set_bit(IOPOLL_F_DISABLE, &iop->state);
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while (test_and_set_bit(IOPOLL_F_SCHED, &iop->state))
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msleep(1);
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clear_bit(IOPOLL_F_DISABLE, &iop->state);
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}
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EXPORT_SYMBOL(blk_iopoll_disable);
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/**
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* blk_iopoll_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 blk_iopoll_enable(struct blk_iopoll *iop)
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{
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BUG_ON(!test_bit(IOPOLL_F_SCHED, &iop->state));
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smp_mb__before_atomic();
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clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
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}
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EXPORT_SYMBOL(blk_iopoll_enable);
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/**
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* blk_iopoll_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 this blk_iopoll structure. Before being actively used, the
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* driver must call blk_iopoll_enable().
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**/
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void blk_iopoll_init(struct blk_iopoll *iop, int weight, blk_iopoll_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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set_bit(IOPOLL_F_SCHED, &iop->state);
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}
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EXPORT_SYMBOL(blk_iopoll_init);
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static int blk_iopoll_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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/*
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* If a CPU goes away, splice its entries to the current CPU
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* and trigger a run of the softirq
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*/
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if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
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int cpu = (unsigned long) hcpu;
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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(BLOCK_IOPOLL_SOFTIRQ);
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local_irq_enable();
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}
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return NOTIFY_OK;
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}
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static struct notifier_block blk_iopoll_cpu_notifier = {
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.notifier_call = blk_iopoll_cpu_notify,
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};
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static __init int blk_iopoll_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(BLOCK_IOPOLL_SOFTIRQ, blk_iopoll_softirq);
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register_hotcpu_notifier(&blk_iopoll_cpu_notifier);
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return 0;
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}
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subsys_initcall(blk_iopoll_setup);
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