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Jens Axboe5e605b62009-08-05 09:07:21 +02001/*
2 * Functions related to interrupt-poll handling in the block layer. This
3 * is similar to NAPI for network devices.
4 */
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/init.h>
8#include <linux/bio.h>
9#include <linux/blkdev.h>
10#include <linux/interrupt.h>
11#include <linux/cpu.h>
12#include <linux/blk-iopoll.h>
13#include <linux/delay.h>
14
15#include "blk.h"
16
Jens Axboe37867ae2009-08-06 20:50:48 +020017static unsigned int blk_iopoll_budget __read_mostly = 256;
18
Jens Axboe5e605b62009-08-05 09:07:21 +020019static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
20
21/**
22 * blk_iopoll_sched - Schedule a run of the iopoll handler
23 * @iop: The parent iopoll structure
24 *
25 * Description:
Jens Axboe1badcfb2009-08-06 20:49:14 +020026 * Add this blk_iopoll structure to the pending poll list and trigger the
27 * raise of the blk iopoll softirq. The driver must already have gotten a
André Goddard Rosaaf901ca2009-11-14 13:09:05 -020028 * successful return from blk_iopoll_sched_prep() before calling this.
Jens Axboe5e605b62009-08-05 09:07:21 +020029 **/
30void blk_iopoll_sched(struct blk_iopoll *iop)
31{
32 unsigned long flags;
33
34 local_irq_save(flags);
Christoph Lameter170d8002013-10-15 12:22:29 -060035 list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
Jens Axboe5e605b62009-08-05 09:07:21 +020036 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
37 local_irq_restore(flags);
38}
39EXPORT_SYMBOL(blk_iopoll_sched);
40
41/**
42 * __blk_iopoll_complete - Mark this @iop as un-polled again
43 * @iop: The parent iopoll structure
44 *
45 * Description:
Jens Axboe1badcfb2009-08-06 20:49:14 +020046 * See blk_iopoll_complete(). This function must be called with interrupts
47 * disabled.
Jens Axboe5e605b62009-08-05 09:07:21 +020048 **/
49void __blk_iopoll_complete(struct blk_iopoll *iop)
50{
51 list_del(&iop->list);
52 smp_mb__before_clear_bit();
53 clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
54}
55EXPORT_SYMBOL(__blk_iopoll_complete);
56
57/**
58 * blk_iopoll_complete - Mark this @iop as un-polled again
59 * @iop: The parent iopoll structure
60 *
61 * Description:
Jens Axboe1badcfb2009-08-06 20:49:14 +020062 * If a driver consumes less than the assigned budget in its run of the
63 * iopoll handler, it'll end the polled mode by calling this function. The
64 * iopoll handler will not be invoked again before blk_iopoll_sched_prep()
65 * is called.
Jens Axboe5e605b62009-08-05 09:07:21 +020066 **/
67void blk_iopoll_complete(struct blk_iopoll *iopoll)
68{
69 unsigned long flags;
70
71 local_irq_save(flags);
72 __blk_iopoll_complete(iopoll);
73 local_irq_restore(flags);
74}
75EXPORT_SYMBOL(blk_iopoll_complete);
76
77static void blk_iopoll_softirq(struct softirq_action *h)
78{
Christoph Lameter170d8002013-10-15 12:22:29 -060079 struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
Jens Axboe37867ae2009-08-06 20:50:48 +020080 int rearm = 0, budget = blk_iopoll_budget;
Jens Axboe5e605b62009-08-05 09:07:21 +020081 unsigned long start_time = jiffies;
Jens Axboe5e605b62009-08-05 09:07:21 +020082
83 local_irq_disable();
84
85 while (!list_empty(list)) {
86 struct blk_iopoll *iop;
87 int work, weight;
88
89 /*
90 * If softirq window is exhausted then punt.
91 */
92 if (budget <= 0 || time_after(jiffies, start_time)) {
93 rearm = 1;
94 break;
95 }
96
97 local_irq_enable();
98
99 /* Even though interrupts have been re-enabled, this
100 * access is safe because interrupts can only add new
101 * entries to the tail of this list, and only ->poll()
102 * calls can remove this head entry from the list.
103 */
104 iop = list_entry(list->next, struct blk_iopoll, list);
105
106 weight = iop->weight;
107 work = 0;
108 if (test_bit(IOPOLL_F_SCHED, &iop->state))
109 work = iop->poll(iop, weight);
110
111 budget -= work;
112
113 local_irq_disable();
114
Jens Axboefca51d62009-08-06 20:53:23 +0200115 /*
116 * Drivers must not modify the iopoll state, if they
117 * consume their assigned weight (or more, some drivers can't
118 * easily just stop processing, they have to complete an
119 * entire mask of commands).In such cases this code
120 * still "owns" the iopoll instance and therefore can
Jens Axboe5e605b62009-08-05 09:07:21 +0200121 * move the instance around on the list at-will.
122 */
123 if (work >= weight) {
124 if (blk_iopoll_disable_pending(iop))
125 __blk_iopoll_complete(iop);
126 else
127 list_move_tail(&iop->list, list);
128 }
129 }
130
131 if (rearm)
132 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
133
134 local_irq_enable();
135}
136
137/**
138 * blk_iopoll_disable - Disable iopoll on this @iop
139 * @iop: The parent iopoll structure
140 *
141 * Description:
142 * Disable io polling and wait for any pending callbacks to have completed.
143 **/
144void blk_iopoll_disable(struct blk_iopoll *iop)
145{
146 set_bit(IOPOLL_F_DISABLE, &iop->state);
147 while (test_and_set_bit(IOPOLL_F_SCHED, &iop->state))
148 msleep(1);
149 clear_bit(IOPOLL_F_DISABLE, &iop->state);
150}
151EXPORT_SYMBOL(blk_iopoll_disable);
152
153/**
154 * blk_iopoll_enable - Enable iopoll on this @iop
155 * @iop: The parent iopoll structure
156 *
157 * Description:
Jens Axboe1badcfb2009-08-06 20:49:14 +0200158 * Enable iopoll on this @iop. Note that the handler run will not be
159 * scheduled, it will only mark it as active.
Jens Axboe5e605b62009-08-05 09:07:21 +0200160 **/
161void blk_iopoll_enable(struct blk_iopoll *iop)
162{
163 BUG_ON(!test_bit(IOPOLL_F_SCHED, &iop->state));
Jens Axboe1badcfb2009-08-06 20:49:14 +0200164 smp_mb__before_clear_bit();
Jens Axboe5e605b62009-08-05 09:07:21 +0200165 clear_bit_unlock(IOPOLL_F_SCHED, &iop->state);
166}
167EXPORT_SYMBOL(blk_iopoll_enable);
168
169/**
170 * blk_iopoll_init - Initialize this @iop
171 * @iop: The parent iopoll structure
172 * @weight: The default weight (or command completion budget)
173 * @poll_fn: The handler to invoke
174 *
175 * Description:
Jens Axboe1badcfb2009-08-06 20:49:14 +0200176 * Initialize this blk_iopoll structure. Before being actively used, the
177 * driver must call blk_iopoll_enable().
Jens Axboe5e605b62009-08-05 09:07:21 +0200178 **/
179void blk_iopoll_init(struct blk_iopoll *iop, int weight, blk_iopoll_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 set_bit(IOPOLL_F_SCHED, &iop->state);
186}
187EXPORT_SYMBOL(blk_iopoll_init);
188
Paul Gortmaker0b776b02013-06-19 15:26:23 -0400189static int blk_iopoll_cpu_notify(struct notifier_block *self,
190 unsigned long action, void *hcpu)
Jens Axboe5e605b62009-08-05 09:07:21 +0200191{
192 /*
193 * If a CPU goes away, splice its entries to the current CPU
194 * and trigger a run of the softirq
195 */
196 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
197 int cpu = (unsigned long) hcpu;
198
199 local_irq_disable();
200 list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
Christoph Lameter170d8002013-10-15 12:22:29 -0600201 this_cpu_ptr(&blk_cpu_iopoll));
Jens Axboea33dac22009-08-06 20:53:45 +0200202 __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
Jens Axboe5e605b62009-08-05 09:07:21 +0200203 local_irq_enable();
204 }
205
206 return NOTIFY_OK;
207}
208
Paul Gortmaker0b776b02013-06-19 15:26:23 -0400209static struct notifier_block blk_iopoll_cpu_notifier = {
Jens Axboe5e605b62009-08-05 09:07:21 +0200210 .notifier_call = blk_iopoll_cpu_notify,
211};
212
213static __init int blk_iopoll_setup(void)
214{
215 int i;
216
217 for_each_possible_cpu(i)
218 INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
219
220 open_softirq(BLOCK_IOPOLL_SOFTIRQ, blk_iopoll_softirq);
221 register_hotcpu_notifier(&blk_iopoll_cpu_notifier);
222 return 0;
223}
224subsys_initcall(blk_iopoll_setup);