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Commit | Line | Data |
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b646fc59 JA |
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> | |
39be3501 | 11 | #include <linux/sched.h> |
b646fc59 JA |
12 | |
13 | #include "blk.h" | |
14 | ||
15 | static DEFINE_PER_CPU(struct list_head, blk_cpu_done); | |
16 | ||
c7c22e4d JA |
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(); | |
170d800a | 26 | cpu_list = this_cpu_ptr(&blk_cpu_done); |
c7c22e4d JA |
27 | list_replace_init(cpu_list, &local_list); |
28 | local_irq_enable(); | |
29 | ||
30 | while (!list_empty(&local_list)) { | |
31 | struct request *rq; | |
32 | ||
6d113398 JK |
33 | rq = list_entry(local_list.next, struct request, queuelist); |
34 | list_del_init(&rq->queuelist); | |
c7c22e4d JA |
35 | rq->q->softirq_done_fn(rq); |
36 | } | |
37 | } | |
38 | ||
0a06ff06 | 39 | #ifdef CONFIG_SMP |
c7c22e4d JA |
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); | |
170d800a | 47 | list = this_cpu_ptr(&blk_cpu_done); |
6d113398 JK |
48 | /* |
49 | * We reuse queuelist for a list of requests to process. Since the | |
50 | * queuelist is used by the block layer only for requests waiting to be | |
51 | * submitted to the device it is unused now. | |
52 | */ | |
53 | list_add_tail(&rq->queuelist, list); | |
c7c22e4d | 54 | |
6d113398 | 55 | if (list->next == &rq->queuelist) |
c7c22e4d JA |
56 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
57 | ||
58 | local_irq_restore(flags); | |
59 | } | |
60 | ||
61 | /* | |
62 | * Setup and invoke a run of 'trigger_softirq' on the given cpu. | |
63 | */ | |
64 | static int raise_blk_irq(int cpu, struct request *rq) | |
65 | { | |
66 | if (cpu_online(cpu)) { | |
67 | struct call_single_data *data = &rq->csd; | |
68 | ||
69 | data->func = trigger_softirq; | |
70 | data->info = rq; | |
71 | data->flags = 0; | |
72 | ||
c46fff2a | 73 | smp_call_function_single_async(cpu, data); |
c7c22e4d JA |
74 | return 0; |
75 | } | |
76 | ||
77 | return 1; | |
78 | } | |
0a06ff06 | 79 | #else /* CONFIG_SMP */ |
c7c22e4d JA |
80 | static int raise_blk_irq(int cpu, struct request *rq) |
81 | { | |
82 | return 1; | |
83 | } | |
84 | #endif | |
85 | ||
0b776b06 PG |
86 | static int blk_cpu_notify(struct notifier_block *self, unsigned long action, |
87 | void *hcpu) | |
b646fc59 JA |
88 | { |
89 | /* | |
90 | * If a CPU goes away, splice its entries to the current CPU | |
91 | * and trigger a run of the softirq | |
92 | */ | |
93 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { | |
94 | int cpu = (unsigned long) hcpu; | |
95 | ||
96 | local_irq_disable(); | |
97 | list_splice_init(&per_cpu(blk_cpu_done, cpu), | |
170d800a | 98 | this_cpu_ptr(&blk_cpu_done)); |
b646fc59 JA |
99 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
100 | local_irq_enable(); | |
101 | } | |
102 | ||
103 | return NOTIFY_OK; | |
104 | } | |
105 | ||
0b776b06 | 106 | static struct notifier_block blk_cpu_notifier = { |
b646fc59 JA |
107 | .notifier_call = blk_cpu_notify, |
108 | }; | |
109 | ||
242f9dcb | 110 | void __blk_complete_request(struct request *req) |
b646fc59 | 111 | { |
39be3501 | 112 | int ccpu, cpu; |
c7c22e4d | 113 | struct request_queue *q = req->q; |
b646fc59 | 114 | unsigned long flags; |
39be3501 | 115 | bool shared = false; |
b646fc59 | 116 | |
c7c22e4d | 117 | BUG_ON(!q->softirq_done_fn); |
b646fc59 JA |
118 | |
119 | local_irq_save(flags); | |
c7c22e4d | 120 | cpu = smp_processor_id(); |
b646fc59 | 121 | |
c7c22e4d JA |
122 | /* |
123 | * Select completion CPU | |
124 | */ | |
8ad6a56f | 125 | if (req->cpu != -1) { |
c7c22e4d | 126 | ccpu = req->cpu; |
39be3501 PZ |
127 | if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) |
128 | shared = cpus_share_cache(cpu, ccpu); | |
5757a6d7 | 129 | } else |
c7c22e4d JA |
130 | ccpu = cpu; |
131 | ||
bcf30e75 | 132 | /* |
39be3501 PZ |
133 | * If current CPU and requested CPU share a cache, run the softirq on |
134 | * the current CPU. One might concern this is just like | |
bcf30e75 SL |
135 | * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is |
136 | * running in interrupt handler, and currently I/O controller doesn't | |
137 | * support multiple interrupts, so current CPU is unique actually. This | |
138 | * avoids IPI sending from current CPU to the first CPU of a group. | |
139 | */ | |
39be3501 | 140 | if (ccpu == cpu || shared) { |
c7c22e4d JA |
141 | struct list_head *list; |
142 | do_local: | |
170d800a | 143 | list = this_cpu_ptr(&blk_cpu_done); |
6d113398 | 144 | list_add_tail(&req->queuelist, list); |
c7c22e4d JA |
145 | |
146 | /* | |
147 | * if the list only contains our just added request, | |
148 | * signal a raise of the softirq. If there are already | |
149 | * entries there, someone already raised the irq but it | |
150 | * hasn't run yet. | |
151 | */ | |
6d113398 | 152 | if (list->next == &req->queuelist) |
c7c22e4d JA |
153 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
154 | } else if (raise_blk_irq(ccpu, req)) | |
155 | goto do_local; | |
b646fc59 JA |
156 | |
157 | local_irq_restore(flags); | |
158 | } | |
242f9dcb JA |
159 | |
160 | /** | |
161 | * blk_complete_request - end I/O on a request | |
162 | * @req: the request being processed | |
163 | * | |
164 | * Description: | |
165 | * Ends all I/O on a request. It does not handle partial completions, | |
166 | * unless the driver actually implements this in its completion callback | |
167 | * through requeueing. The actual completion happens out-of-order, | |
168 | * through a softirq handler. The user must have registered a completion | |
169 | * callback through blk_queue_softirq_done(). | |
170 | **/ | |
171 | void blk_complete_request(struct request *req) | |
172 | { | |
581d4e28 JA |
173 | if (unlikely(blk_should_fake_timeout(req->q))) |
174 | return; | |
242f9dcb JA |
175 | if (!blk_mark_rq_complete(req)) |
176 | __blk_complete_request(req); | |
177 | } | |
b646fc59 JA |
178 | EXPORT_SYMBOL(blk_complete_request); |
179 | ||
3c18ce71 | 180 | static __init int blk_softirq_init(void) |
b646fc59 JA |
181 | { |
182 | int i; | |
183 | ||
184 | for_each_possible_cpu(i) | |
185 | INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); | |
186 | ||
187 | open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); | |
188 | register_hotcpu_notifier(&blk_cpu_notifier); | |
189 | return 0; | |
190 | } | |
191 | subsys_initcall(blk_softirq_init); |