blob: 06cf9807f49a3be1742a632f9be61c0232fcaf5c
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 __latent_entropy 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, ipi_list); |
34 | list_del_init(&rq->ipi_list); |
35 | rq->q->softirq_done_fn(rq); |
36 | } |
37 | } |
38 | |
39 | #ifdef CONFIG_SMP |
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->ipi_list, list); |
49 | |
50 | if (list->next == &rq->ipi_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_async(cpu, data); |
69 | return 0; |
70 | } |
71 | |
72 | return 1; |
73 | } |
74 | #else /* CONFIG_SMP */ |
75 | static int raise_blk_irq(int cpu, struct request *rq) |
76 | { |
77 | return 1; |
78 | } |
79 | #endif |
80 | |
81 | static int blk_softirq_cpu_dead(unsigned int cpu) |
82 | { |
83 | /* |
84 | * If a CPU goes away, splice its entries to the current CPU |
85 | * and trigger a run of the softirq |
86 | */ |
87 | local_irq_disable(); |
88 | list_splice_init(&per_cpu(blk_cpu_done, cpu), |
89 | this_cpu_ptr(&blk_cpu_done)); |
90 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
91 | local_irq_enable(); |
92 | |
93 | return 0; |
94 | } |
95 | |
96 | void __blk_complete_request(struct request *req) |
97 | { |
98 | int ccpu, cpu; |
99 | struct request_queue *q = req->q; |
100 | unsigned long flags; |
101 | bool shared = false; |
102 | |
103 | BUG_ON(!q->softirq_done_fn); |
104 | |
105 | local_irq_save(flags); |
106 | cpu = smp_processor_id(); |
107 | |
108 | /* |
109 | * Select completion CPU |
110 | */ |
111 | if (req->cpu != -1) { |
112 | ccpu = req->cpu; |
113 | if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) |
114 | shared = cpus_share_cache(cpu, ccpu); |
115 | } else |
116 | ccpu = cpu; |
117 | |
118 | /* |
119 | * If current CPU and requested CPU share a cache, run the softirq on |
120 | * the current CPU. One might concern this is just like |
121 | * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is |
122 | * running in interrupt handler, and currently I/O controller doesn't |
123 | * support multiple interrupts, so current CPU is unique actually. This |
124 | * avoids IPI sending from current CPU to the first CPU of a group. |
125 | */ |
126 | if (ccpu == cpu || shared) { |
127 | struct list_head *list; |
128 | do_local: |
129 | list = this_cpu_ptr(&blk_cpu_done); |
130 | list_add_tail(&req->ipi_list, list); |
131 | |
132 | /* |
133 | * if the list only contains our just added request, |
134 | * signal a raise of the softirq. If there are already |
135 | * entries there, someone already raised the irq but it |
136 | * hasn't run yet. |
137 | */ |
138 | if (list->next == &req->ipi_list) |
139 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
140 | } else if (raise_blk_irq(ccpu, req)) |
141 | goto do_local; |
142 | |
143 | local_irq_restore(flags); |
144 | } |
145 | |
146 | /** |
147 | * blk_complete_request - end I/O on a request |
148 | * @req: the request being processed |
149 | * |
150 | * Description: |
151 | * Ends all I/O on a request. It does not handle partial completions, |
152 | * unless the driver actually implements this in its completion callback |
153 | * through requeueing. The actual completion happens out-of-order, |
154 | * through a softirq handler. The user must have registered a completion |
155 | * callback through blk_queue_softirq_done(). |
156 | **/ |
157 | void blk_complete_request(struct request *req) |
158 | { |
159 | if (unlikely(blk_should_fake_timeout(req->q))) |
160 | return; |
161 | if (!blk_mark_rq_complete(req)) |
162 | __blk_complete_request(req); |
163 | } |
164 | EXPORT_SYMBOL(blk_complete_request); |
165 | |
166 | static __init int blk_softirq_init(void) |
167 | { |
168 | int i; |
169 | |
170 | for_each_possible_cpu(i) |
171 | INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); |
172 | |
173 | open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); |
174 | cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD, |
175 | "block/softirq:dead", NULL, |
176 | blk_softirq_cpu_dead); |
177 | return 0; |
178 | } |
179 | subsys_initcall(blk_softirq_init); |
180 |