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1 | /* | |
2 | * Functions related to softirq rq completions | |
3 | */ | |
4 | #include <linux/kernel.h> | |
5 | #include <linux/module.h> | |
6 | #include <linux/init.h> | |
7 | #include <linux/bio.h> | |
8 | #include <linux/blkdev.h> | |
9 | #include <linux/interrupt.h> | |
10 | #include <linux/cpu.h> | |
11 | #include <linux/sched.h> | |
12 | ||
13 | #include "blk.h" | |
14 | ||
15 | static DEFINE_PER_CPU(struct list_head, blk_cpu_done); | |
16 | ||
17 | /* | |
18 | * Softirq action handler - move entries to local list and loop over them | |
19 | * while passing them to the queue registered handler. | |
20 | */ | |
21 | static void blk_done_softirq(struct softirq_action *h) | |
22 | { | |
23 | struct list_head *cpu_list, local_list; | |
24 | ||
25 | local_irq_disable(); | |
26 | cpu_list = this_cpu_ptr(&blk_cpu_done); | |
27 | list_replace_init(cpu_list, &local_list); | |
28 | local_irq_enable(); | |
29 | ||
30 | while (!list_empty(&local_list)) { | |
31 | struct request *rq; | |
32 | ||
33 | rq = list_entry(local_list.next, struct request, csd.list); | |
34 | list_del_init(&rq->csd.list); | |
35 | rq->q->softirq_done_fn(rq); | |
36 | } | |
37 | } | |
38 | ||
39 | #if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS) | |
40 | static void trigger_softirq(void *data) | |
41 | { | |
42 | struct request *rq = data; | |
43 | unsigned long flags; | |
44 | struct list_head *list; | |
45 | ||
46 | local_irq_save(flags); | |
47 | list = this_cpu_ptr(&blk_cpu_done); | |
48 | list_add_tail(&rq->csd.list, list); | |
49 | ||
50 | if (list->next == &rq->csd.list) | |
51 | raise_softirq_irqoff(BLOCK_SOFTIRQ); | |
52 | ||
53 | local_irq_restore(flags); | |
54 | } | |
55 | ||
56 | /* | |
57 | * Setup and invoke a run of 'trigger_softirq' on the given cpu. | |
58 | */ | |
59 | static int raise_blk_irq(int cpu, struct request *rq) | |
60 | { | |
61 | if (cpu_online(cpu)) { | |
62 | struct call_single_data *data = &rq->csd; | |
63 | ||
64 | data->func = trigger_softirq; | |
65 | data->info = rq; | |
66 | data->flags = 0; | |
67 | ||
68 | __smp_call_function_single(cpu, data, 0); | |
69 | return 0; | |
70 | } | |
71 | ||
72 | return 1; | |
73 | } | |
74 | #else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */ | |
75 | static int raise_blk_irq(int cpu, struct request *rq) | |
76 | { | |
77 | return 1; | |
78 | } | |
79 | #endif | |
80 | ||
81 | static int blk_cpu_notify(struct notifier_block *self, unsigned long action, | |
82 | void *hcpu) | |
83 | { | |
84 | /* | |
85 | * If a CPU goes away, splice its entries to the current CPU | |
86 | * and trigger a run of the softirq | |
87 | */ | |
88 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { | |
89 | int cpu = (unsigned long) hcpu; | |
90 | ||
91 | local_irq_disable(); | |
92 | list_splice_init(&per_cpu(blk_cpu_done, cpu), | |
93 | this_cpu_ptr(&blk_cpu_done)); | |
94 | raise_softirq_irqoff(BLOCK_SOFTIRQ); | |
95 | local_irq_enable(); | |
96 | } | |
97 | ||
98 | return NOTIFY_OK; | |
99 | } | |
100 | ||
101 | static struct notifier_block blk_cpu_notifier = { | |
102 | .notifier_call = blk_cpu_notify, | |
103 | }; | |
104 | ||
105 | void __blk_complete_request(struct request *req) | |
106 | { | |
107 | int ccpu, cpu; | |
108 | struct request_queue *q = req->q; | |
109 | unsigned long flags; | |
110 | bool shared = false; | |
111 | ||
112 | BUG_ON(!q->softirq_done_fn); | |
113 | ||
114 | local_irq_save(flags); | |
115 | cpu = smp_processor_id(); | |
116 | ||
117 | /* | |
118 | * Select completion CPU | |
119 | */ | |
120 | if (req->cpu != -1) { | |
121 | ccpu = req->cpu; | |
122 | if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) | |
123 | shared = cpus_share_cache(cpu, ccpu); | |
124 | } else | |
125 | ccpu = cpu; | |
126 | ||
127 | /* | |
128 | * If current CPU and requested CPU share a cache, run the softirq on | |
129 | * the current CPU. One might concern this is just like | |
130 | * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is | |
131 | * running in interrupt handler, and currently I/O controller doesn't | |
132 | * support multiple interrupts, so current CPU is unique actually. This | |
133 | * avoids IPI sending from current CPU to the first CPU of a group. | |
134 | */ | |
135 | if (ccpu == cpu || shared) { | |
136 | struct list_head *list; | |
137 | do_local: | |
138 | list = this_cpu_ptr(&blk_cpu_done); | |
139 | list_add_tail(&req->csd.list, list); | |
140 | ||
141 | /* | |
142 | * if the list only contains our just added request, | |
143 | * signal a raise of the softirq. If there are already | |
144 | * entries there, someone already raised the irq but it | |
145 | * hasn't run yet. | |
146 | */ | |
147 | if (list->next == &req->csd.list) | |
148 | raise_softirq_irqoff(BLOCK_SOFTIRQ); | |
149 | } else if (raise_blk_irq(ccpu, req)) | |
150 | goto do_local; | |
151 | ||
152 | local_irq_restore(flags); | |
153 | } | |
154 | ||
155 | /** | |
156 | * blk_complete_request - end I/O on a request | |
157 | * @req: the request being processed | |
158 | * | |
159 | * Description: | |
160 | * Ends all I/O on a request. It does not handle partial completions, | |
161 | * unless the driver actually implements this in its completion callback | |
162 | * through requeueing. The actual completion happens out-of-order, | |
163 | * through a softirq handler. The user must have registered a completion | |
164 | * callback through blk_queue_softirq_done(). | |
165 | **/ | |
166 | void blk_complete_request(struct request *req) | |
167 | { | |
168 | if (unlikely(blk_should_fake_timeout(req->q))) | |
169 | return; | |
170 | if (!blk_mark_rq_complete(req)) | |
171 | __blk_complete_request(req); | |
172 | } | |
173 | EXPORT_SYMBOL(blk_complete_request); | |
174 | ||
175 | static __init int blk_softirq_init(void) | |
176 | { | |
177 | int i; | |
178 | ||
179 | for_each_possible_cpu(i) | |
180 | INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); | |
181 | ||
182 | open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); | |
183 | register_hotcpu_notifier(&blk_cpu_notifier); | |
184 | return 0; | |
185 | } | |
186 | subsys_initcall(blk_softirq_init); |