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1 | // SPDX-License-Identifier: GPL-2.0 | |
2 | /* | |
3 | * Functions related to softirq rq completions | |
4 | */ | |
5 | #include <linux/kernel.h> | |
6 | #include <linux/module.h> | |
7 | #include <linux/init.h> | |
8 | #include <linux/bio.h> | |
9 | #include <linux/blkdev.h> | |
10 | #include <linux/interrupt.h> | |
11 | #include <linux/cpu.h> | |
12 | #include <linux/sched.h> | |
13 | #include <linux/sched/topology.h> | |
14 | ||
15 | #include "blk.h" | |
16 | ||
17 | static DEFINE_PER_CPU(struct list_head, blk_cpu_done); | |
18 | ||
19 | /* | |
20 | * Softirq action handler - move entries to local list and loop over them | |
21 | * while passing them to the queue registered handler. | |
22 | */ | |
23 | static __latent_entropy void blk_done_softirq(struct softirq_action *h) | |
24 | { | |
25 | struct list_head *cpu_list, local_list; | |
26 | ||
27 | local_irq_disable(); | |
28 | cpu_list = this_cpu_ptr(&blk_cpu_done); | |
29 | list_replace_init(cpu_list, &local_list); | |
30 | local_irq_enable(); | |
31 | ||
32 | while (!list_empty(&local_list)) { | |
33 | struct request *rq; | |
34 | ||
35 | rq = list_entry(local_list.next, struct request, ipi_list); | |
36 | list_del_init(&rq->ipi_list); | |
37 | rq->q->softirq_done_fn(rq); | |
38 | } | |
39 | } | |
40 | ||
41 | #ifdef CONFIG_SMP | |
42 | static void trigger_softirq(void *data) | |
43 | { | |
44 | struct request *rq = data; | |
45 | unsigned long flags; | |
46 | struct list_head *list; | |
47 | ||
48 | local_irq_save(flags); | |
49 | list = this_cpu_ptr(&blk_cpu_done); | |
50 | list_add_tail(&rq->ipi_list, list); | |
51 | ||
52 | if (list->next == &rq->ipi_list) | |
53 | raise_softirq_irqoff(BLOCK_SOFTIRQ); | |
54 | ||
55 | local_irq_restore(flags); | |
56 | } | |
57 | ||
58 | /* | |
59 | * Setup and invoke a run of 'trigger_softirq' on the given cpu. | |
60 | */ | |
61 | static int raise_blk_irq(int cpu, struct request *rq) | |
62 | { | |
63 | if (cpu_online(cpu)) { | |
64 | call_single_data_t *data = &rq->csd; | |
65 | ||
66 | data->func = trigger_softirq; | |
67 | data->info = rq; | |
68 | data->flags = 0; | |
69 | ||
70 | smp_call_function_single_async(cpu, data); | |
71 | return 0; | |
72 | } | |
73 | ||
74 | return 1; | |
75 | } | |
76 | #else /* CONFIG_SMP */ | |
77 | static int raise_blk_irq(int cpu, struct request *rq) | |
78 | { | |
79 | return 1; | |
80 | } | |
81 | #endif | |
82 | ||
83 | static int blk_softirq_cpu_dead(unsigned int cpu) | |
84 | { | |
85 | /* | |
86 | * If a CPU goes away, splice its entries to the current CPU | |
87 | * and trigger a run of the softirq | |
88 | */ | |
89 | local_irq_disable(); | |
90 | list_splice_init(&per_cpu(blk_cpu_done, cpu), | |
91 | this_cpu_ptr(&blk_cpu_done)); | |
92 | raise_softirq_irqoff(BLOCK_SOFTIRQ); | |
93 | local_irq_enable(); | |
94 | ||
95 | return 0; | |
96 | } | |
97 | ||
98 | void __blk_complete_request(struct request *req) | |
99 | { | |
100 | int ccpu, cpu; | |
101 | struct request_queue *q = req->q; | |
102 | unsigned long flags; | |
103 | bool shared = false; | |
104 | ||
105 | BUG_ON(!q->softirq_done_fn); | |
106 | ||
107 | local_irq_save(flags); | |
108 | cpu = smp_processor_id(); | |
109 | ||
110 | /* | |
111 | * Select completion CPU | |
112 | */ | |
113 | if (req->cpu != -1) { | |
114 | ccpu = req->cpu; | |
115 | if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) | |
116 | shared = cpus_share_cache(cpu, ccpu); | |
117 | } else | |
118 | ccpu = cpu; | |
119 | ||
120 | /* | |
121 | * If current CPU and requested CPU share a cache, run the softirq on | |
122 | * the current CPU. One might concern this is just like | |
123 | * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is | |
124 | * running in interrupt handler, and currently I/O controller doesn't | |
125 | * support multiple interrupts, so current CPU is unique actually. This | |
126 | * avoids IPI sending from current CPU to the first CPU of a group. | |
127 | */ | |
128 | if (ccpu == cpu || shared) { | |
129 | struct list_head *list; | |
130 | do_local: | |
131 | list = this_cpu_ptr(&blk_cpu_done); | |
132 | list_add_tail(&req->ipi_list, list); | |
133 | ||
134 | /* | |
135 | * if the list only contains our just added request, | |
136 | * signal a raise of the softirq. If there are already | |
137 | * entries there, someone already raised the irq but it | |
138 | * hasn't run yet. | |
139 | */ | |
140 | if (list->next == &req->ipi_list) | |
141 | raise_softirq_irqoff(BLOCK_SOFTIRQ); | |
142 | } else if (raise_blk_irq(ccpu, req)) | |
143 | goto do_local; | |
144 | ||
145 | local_irq_restore(flags); | |
146 | } | |
147 | ||
148 | /** | |
149 | * blk_complete_request - end I/O on a request | |
150 | * @req: the request being processed | |
151 | * | |
152 | * Description: | |
153 | * Ends all I/O on a request. It does not handle partial completions, | |
154 | * unless the driver actually implements this in its completion callback | |
155 | * through requeueing. The actual completion happens out-of-order, | |
156 | * through a softirq handler. The user must have registered a completion | |
157 | * callback through blk_queue_softirq_done(). | |
158 | **/ | |
159 | void blk_complete_request(struct request *req) | |
160 | { | |
161 | if (unlikely(blk_should_fake_timeout(req->q))) | |
162 | return; | |
163 | if (!blk_mark_rq_complete(req)) | |
164 | __blk_complete_request(req); | |
165 | } | |
166 | EXPORT_SYMBOL(blk_complete_request); | |
167 | ||
168 | static __init int blk_softirq_init(void) | |
169 | { | |
170 | int i; | |
171 | ||
172 | for_each_possible_cpu(i) | |
173 | INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); | |
174 | ||
175 | open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); | |
176 | cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD, | |
177 | "block/softirq:dead", NULL, | |
178 | blk_softirq_cpu_dead); | |
179 | return 0; | |
180 | } | |
181 | subsys_initcall(blk_softirq_init); |