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1// SPDX-License-Identifier: GPL-2.02/*3 * Functions related to interrupt-poll handling in the block layer. This4 * is similar to NAPI for network devices.5 */6#include <linux/kernel.h>7#include <linux/module.h>8#include <linux/init.h>9#include <linux/bio.h>10#include <linux/interrupt.h>11#include <linux/cpu.h>12#include <linux/irq_poll.h>13#include <linux/delay.h>14 15static unsigned int irq_poll_budget __read_mostly = 256;16 17static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);18 19/**20 * irq_poll_sched - Schedule a run of the iopoll handler21 * @iop: The parent iopoll structure22 *23 * Description:24 * Add this irq_poll structure to the pending poll list and trigger the25 * raise of the blk iopoll softirq.26 **/27void irq_poll_sched(struct irq_poll *iop)28{29 unsigned long flags;30 31 if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))32 return;33 if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))34 return;35 36 local_irq_save(flags);37 list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));38 raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);39 local_irq_restore(flags);40}41EXPORT_SYMBOL(irq_poll_sched);42 43/**44 * __irq_poll_complete - Mark this @iop as un-polled again45 * @iop: The parent iopoll structure46 *47 * Description:48 * See irq_poll_complete(). This function must be called with interrupts49 * disabled.50 **/51static void __irq_poll_complete(struct irq_poll *iop)52{53 list_del(&iop->list);54 smp_mb__before_atomic();55 clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);56}57 58/**59 * irq_poll_complete - Mark this @iop as un-polled again60 * @iop: The parent iopoll structure61 *62 * Description:63 * If a driver consumes less than the assigned budget in its run of the64 * iopoll handler, it'll end the polled mode by calling this function. The65 * iopoll handler will not be invoked again before irq_poll_sched()66 * is called.67 **/68void irq_poll_complete(struct irq_poll *iop)69{70 unsigned long flags;71 72 local_irq_save(flags);73 __irq_poll_complete(iop);74 local_irq_restore(flags);75}76EXPORT_SYMBOL(irq_poll_complete);77 78static void __latent_entropy irq_poll_softirq(void)79{80 struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);81 int rearm = 0, budget = irq_poll_budget;82 unsigned long start_time = jiffies;83 84 local_irq_disable();85 86 while (!list_empty(list)) {87 struct irq_poll *iop;88 int work, weight;89 90 /*91 * If softirq window is exhausted then punt.92 */93 if (budget <= 0 || time_after(jiffies, start_time)) {94 rearm = 1;95 break;96 }97 98 local_irq_enable();99 100 /* Even though interrupts have been re-enabled, this101 * access is safe because interrupts can only add new102 * entries to the tail of this list, and only ->poll()103 * calls can remove this head entry from the list.104 */105 iop = list_entry(list->next, struct irq_poll, list);106 107 weight = iop->weight;108 work = 0;109 if (test_bit(IRQ_POLL_F_SCHED, &iop->state))110 work = iop->poll(iop, weight);111 112 budget -= work;113 114 local_irq_disable();115 116 /*117 * Drivers must not modify the iopoll state, if they118 * consume their assigned weight (or more, some drivers can't119 * easily just stop processing, they have to complete an120 * entire mask of commands).In such cases this code121 * still "owns" the iopoll instance and therefore can122 * move the instance around on the list at-will.123 */124 if (work >= weight) {125 if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))126 __irq_poll_complete(iop);127 else128 list_move_tail(&iop->list, list);129 }130 }131 132 if (rearm)133 __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);134 135 local_irq_enable();136}137 138/**139 * irq_poll_disable - Disable iopoll on this @iop140 * @iop: The parent iopoll structure141 *142 * Description:143 * Disable io polling and wait for any pending callbacks to have completed.144 **/145void irq_poll_disable(struct irq_poll *iop)146{147 set_bit(IRQ_POLL_F_DISABLE, &iop->state);148 while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))149 msleep(1);150 clear_bit(IRQ_POLL_F_DISABLE, &iop->state);151}152EXPORT_SYMBOL(irq_poll_disable);153 154/**155 * irq_poll_enable - Enable iopoll on this @iop156 * @iop: The parent iopoll structure157 *158 * Description:159 * Enable iopoll on this @iop. Note that the handler run will not be160 * scheduled, it will only mark it as active.161 **/162void irq_poll_enable(struct irq_poll *iop)163{164 BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));165 smp_mb__before_atomic();166 clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);167}168EXPORT_SYMBOL(irq_poll_enable);169 170/**171 * irq_poll_init - Initialize this @iop172 * @iop: The parent iopoll structure173 * @weight: The default weight (or command completion budget)174 * @poll_fn: The handler to invoke175 *176 * Description:177 * Initialize and enable this irq_poll structure.178 **/179void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)180{181 memset(iop, 0, sizeof(*iop));182 INIT_LIST_HEAD(&iop->list);183 iop->weight = weight;184 iop->poll = poll_fn;185}186EXPORT_SYMBOL(irq_poll_init);187 188static int irq_poll_cpu_dead(unsigned int cpu)189{190 /*191 * If a CPU goes away, splice its entries to the current CPU and192 * set the POLL softirq bit. The local_bh_disable()/enable() pair193 * ensures that it is handled. Otherwise the current CPU could194 * reach idle with the POLL softirq pending.195 */196 local_bh_disable();197 local_irq_disable();198 list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),199 this_cpu_ptr(&blk_cpu_iopoll));200 __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);201 local_irq_enable();202 local_bh_enable();203 204 return 0;205}206 207static __init int irq_poll_setup(void)208{209 int i;210 211 for_each_possible_cpu(i)212 INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));213 214 open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq);215 cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL,216 irq_poll_cpu_dead);217 return 0;218}219subsys_initcall(irq_poll_setup);220