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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> | |
9 | #include <linux/interrupt.h> | |
10 | #include <linux/cpu.h> | |
11 | #include <linux/irq_poll.h> | |
12 | #include <linux/delay.h> | |
13 | ||
14 | static unsigned int irq_poll_budget __read_mostly = 256; | |
15 | ||
16 | static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll); | |
17 | ||
18 | /** | |
19 | * irq_poll_sched - Schedule a run of the iopoll handler | |
20 | * @iop: The parent iopoll structure | |
21 | * | |
22 | * Description: | |
23 | * Add this irq_poll structure to the pending poll list and trigger the | |
24 | * raise of the blk iopoll softirq. | |
25 | **/ | |
26 | void irq_poll_sched(struct irq_poll *iop) | |
27 | { | |
28 | unsigned long flags; | |
29 | ||
30 | if (test_bit(IRQ_POLL_F_DISABLE, &iop->state)) | |
31 | return; | |
32 | if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state)) | |
33 | return; | |
34 | ||
35 | local_irq_save(flags); | |
36 | list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll)); | |
37 | __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); | |
38 | local_irq_restore(flags); | |
39 | } | |
40 | EXPORT_SYMBOL(irq_poll_sched); | |
41 | ||
42 | /** | |
43 | * __irq_poll_complete - Mark this @iop as un-polled again | |
44 | * @iop: The parent iopoll structure | |
45 | * | |
46 | * Description: | |
47 | * See irq_poll_complete(). This function must be called with interrupts | |
48 | * disabled. | |
49 | **/ | |
50 | static void __irq_poll_complete(struct irq_poll *iop) | |
51 | { | |
52 | list_del(&iop->list); | |
53 | smp_mb__before_atomic(); | |
54 | clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state); | |
55 | } | |
56 | ||
57 | /** | |
58 | * irq_poll_complete - Mark this @iop as un-polled again | |
59 | * @iop: The parent iopoll structure | |
60 | * | |
61 | * Description: | |
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 | |
64 | * iopoll handler will not be invoked again before irq_poll_sched() | |
65 | * is called. | |
66 | **/ | |
67 | void irq_poll_complete(struct irq_poll *iop) | |
68 | { | |
69 | unsigned long flags; | |
70 | ||
71 | local_irq_save(flags); | |
72 | __irq_poll_complete(iop); | |
73 | local_irq_restore(flags); | |
74 | } | |
75 | EXPORT_SYMBOL(irq_poll_complete); | |
76 | ||
77 | static void __latent_entropy irq_poll_softirq(struct softirq_action *h) | |
78 | { | |
79 | struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll); | |
80 | int rearm = 0, budget = irq_poll_budget; | |
81 | unsigned long start_time = jiffies; | |
82 | ||
83 | local_irq_disable(); | |
84 | ||
85 | while (!list_empty(list)) { | |
86 | struct irq_poll *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 irq_poll, list); | |
105 | ||
106 | weight = iop->weight; | |
107 | work = 0; | |
108 | if (test_bit(IRQ_POLL_F_SCHED, &iop->state)) | |
109 | work = iop->poll(iop, weight); | |
110 | ||
111 | budget -= work; | |
112 | ||
113 | local_irq_disable(); | |
114 | ||
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 | |
121 | * move the instance around on the list at-will. | |
122 | */ | |
123 | if (work >= weight) { | |
124 | if (test_bit(IRQ_POLL_F_DISABLE, &iop->state)) | |
125 | __irq_poll_complete(iop); | |
126 | else | |
127 | list_move_tail(&iop->list, list); | |
128 | } | |
129 | } | |
130 | ||
131 | if (rearm) | |
132 | __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); | |
133 | ||
134 | local_irq_enable(); | |
135 | } | |
136 | ||
137 | /** | |
138 | * irq_poll_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 | **/ | |
144 | void irq_poll_disable(struct irq_poll *iop) | |
145 | { | |
146 | set_bit(IRQ_POLL_F_DISABLE, &iop->state); | |
147 | while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state)) | |
148 | msleep(1); | |
149 | clear_bit(IRQ_POLL_F_DISABLE, &iop->state); | |
150 | } | |
151 | EXPORT_SYMBOL(irq_poll_disable); | |
152 | ||
153 | /** | |
154 | * irq_poll_enable - Enable iopoll on this @iop | |
155 | * @iop: The parent iopoll structure | |
156 | * | |
157 | * Description: | |
158 | * Enable iopoll on this @iop. Note that the handler run will not be | |
159 | * scheduled, it will only mark it as active. | |
160 | **/ | |
161 | void irq_poll_enable(struct irq_poll *iop) | |
162 | { | |
163 | BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state)); | |
164 | smp_mb__before_atomic(); | |
165 | clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state); | |
166 | } | |
167 | EXPORT_SYMBOL(irq_poll_enable); | |
168 | ||
169 | /** | |
170 | * irq_poll_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: | |
176 | * Initialize and enable this irq_poll structure. | |
177 | **/ | |
178 | void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn) | |
179 | { | |
180 | memset(iop, 0, sizeof(*iop)); | |
181 | INIT_LIST_HEAD(&iop->list); | |
182 | iop->weight = weight; | |
183 | iop->poll = poll_fn; | |
184 | } | |
185 | EXPORT_SYMBOL(irq_poll_init); | |
186 | ||
187 | static int irq_poll_cpu_dead(unsigned int cpu) | |
188 | { | |
189 | /* | |
190 | * If a CPU goes away, splice its entries to the current CPU | |
191 | * and trigger a run of the softirq | |
192 | */ | |
193 | local_irq_disable(); | |
194 | list_splice_init(&per_cpu(blk_cpu_iopoll, cpu), | |
195 | this_cpu_ptr(&blk_cpu_iopoll)); | |
196 | __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); | |
197 | local_irq_enable(); | |
198 | ||
199 | return 0; | |
200 | } | |
201 | ||
202 | static __init int irq_poll_setup(void) | |
203 | { | |
204 | int i; | |
205 | ||
206 | for_each_possible_cpu(i) | |
207 | INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i)); | |
208 | ||
209 | open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq); | |
210 | cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL, | |
211 | irq_poll_cpu_dead); | |
212 | return 0; | |
213 | } | |
214 | subsys_initcall(irq_poll_setup); |