Merge branch 'drm-rockchip-next-fixes-2016-01-22' of https://github.com/markyzq/kerne...
[linux-2.6-block.git] / lib / irq_poll.c
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1/*
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>
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9#include <linux/interrupt.h>
10#include <linux/cpu.h>
511cbce2 11#include <linux/irq_poll.h>
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12#include <linux/delay.h>
13
511cbce2 14static unsigned int irq_poll_budget __read_mostly = 256;
37867ae7 15
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16static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
17
18/**
511cbce2 19 * irq_poll_sched - Schedule a run of the iopoll handler
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20 * @iop: The parent iopoll structure
21 *
22 * Description:
511cbce2 23 * Add this irq_poll structure to the pending poll list and trigger the
ea51190c 24 * raise of the blk iopoll softirq.
5e605b64 25 **/
511cbce2 26void irq_poll_sched(struct irq_poll *iop)
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27{
28 unsigned long flags;
29
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30 if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
31 return;
2ee177e9 32 if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
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33 return;
34
5e605b64 35 local_irq_save(flags);
170d800a 36 list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
511cbce2 37 __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
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38 local_irq_restore(flags);
39}
511cbce2 40EXPORT_SYMBOL(irq_poll_sched);
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41
42/**
511cbce2 43 * __irq_poll_complete - Mark this @iop as un-polled again
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44 * @iop: The parent iopoll structure
45 *
46 * Description:
511cbce2 47 * See irq_poll_complete(). This function must be called with interrupts
1badcfbd 48 * disabled.
5e605b64 49 **/
83af187d 50static void __irq_poll_complete(struct irq_poll *iop)
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51{
52 list_del(&iop->list);
4e857c58 53 smp_mb__before_atomic();
511cbce2 54 clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
5e605b64 55}
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56
57/**
511cbce2 58 * irq_poll_complete - Mark this @iop as un-polled again
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59 * @iop: The parent iopoll structure
60 *
61 * Description:
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62 * 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
ea51190c 64 * iopoll handler will not be invoked again before irq_poll_sched()
1badcfbd 65 * is called.
5e605b64 66 **/
511cbce2 67void irq_poll_complete(struct irq_poll *iop)
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68{
69 unsigned long flags;
70
71 local_irq_save(flags);
511cbce2 72 __irq_poll_complete(iop);
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73 local_irq_restore(flags);
74}
511cbce2 75EXPORT_SYMBOL(irq_poll_complete);
5e605b64 76
511cbce2 77static void irq_poll_softirq(struct softirq_action *h)
5e605b64 78{
170d800a 79 struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
511cbce2 80 int rearm = 0, budget = irq_poll_budget;
5e605b64 81 unsigned long start_time = jiffies;
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82
83 local_irq_disable();
84
85 while (!list_empty(list)) {
511cbce2 86 struct irq_poll *iop;
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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 */
511cbce2 104 iop = list_entry(list->next, struct irq_poll, list);
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105
106 weight = iop->weight;
107 work = 0;
511cbce2 108 if (test_bit(IRQ_POLL_F_SCHED, &iop->state))
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109 work = iop->poll(iop, weight);
110
111 budget -= work;
112
113 local_irq_disable();
114
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115 /*
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
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121 * move the instance around on the list at-will.
122 */
123 if (work >= weight) {
0bc92ace 124 if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
511cbce2 125 __irq_poll_complete(iop);
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126 else
127 list_move_tail(&iop->list, list);
128 }
129 }
130
131 if (rearm)
511cbce2 132 __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
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133
134 local_irq_enable();
135}
136
137/**
511cbce2 138 * irq_poll_disable - Disable iopoll on this @iop
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139 * @iop: The parent iopoll structure
140 *
141 * Description:
142 * Disable io polling and wait for any pending callbacks to have completed.
143 **/
511cbce2 144void irq_poll_disable(struct irq_poll *iop)
5e605b64 145{
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146 set_bit(IRQ_POLL_F_DISABLE, &iop->state);
147 while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
5e605b64 148 msleep(1);
511cbce2 149 clear_bit(IRQ_POLL_F_DISABLE, &iop->state);
5e605b64 150}
511cbce2 151EXPORT_SYMBOL(irq_poll_disable);
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152
153/**
511cbce2 154 * irq_poll_enable - Enable iopoll on this @iop
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155 * @iop: The parent iopoll structure
156 *
157 * Description:
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158 * Enable iopoll on this @iop. Note that the handler run will not be
159 * scheduled, it will only mark it as active.
5e605b64 160 **/
511cbce2 161void irq_poll_enable(struct irq_poll *iop)
5e605b64 162{
511cbce2 163 BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));
4e857c58 164 smp_mb__before_atomic();
511cbce2 165 clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
5e605b64 166}
511cbce2 167EXPORT_SYMBOL(irq_poll_enable);
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168
169/**
511cbce2 170 * irq_poll_init - Initialize this @iop
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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:
78d0264e 176 * Initialize and enable this irq_poll structure.
5e605b64 177 **/
511cbce2 178void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)
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179{
180 memset(iop, 0, sizeof(*iop));
181 INIT_LIST_HEAD(&iop->list);
182 iop->weight = weight;
183 iop->poll = poll_fn;
5e605b64 184}
511cbce2 185EXPORT_SYMBOL(irq_poll_init);
5e605b64 186
511cbce2 187static int irq_poll_cpu_notify(struct notifier_block *self,
0b776b06 188 unsigned long action, void *hcpu)
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189{
190 /*
191 * If a CPU goes away, splice its entries to the current CPU
192 * and trigger a run of the softirq
193 */
194 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
195 int cpu = (unsigned long) hcpu;
196
197 local_irq_disable();
198 list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
170d800a 199 this_cpu_ptr(&blk_cpu_iopoll));
511cbce2 200 __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
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201 local_irq_enable();
202 }
203
204 return NOTIFY_OK;
205}
206
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207static struct notifier_block irq_poll_cpu_notifier = {
208 .notifier_call = irq_poll_cpu_notify,
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209};
210
511cbce2 211static __init int irq_poll_setup(void)
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212{
213 int i;
214
215 for_each_possible_cpu(i)
216 INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
217
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218 open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq);
219 register_hotcpu_notifier(&irq_poll_cpu_notifier);
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220 return 0;
221}
511cbce2 222subsys_initcall(irq_poll_setup);