6e7ec87d49faa11eabdded4b01adf33ceaae9037
[linux-2.6-microblaze.git] / block / blk-softirq.c
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->mq_ops->complete(rq);
38         }
39 }
40
41 #ifdef CONFIG_SMP
42 static void trigger_softirq(void *data)
43 {
44         struct request *rq = data;
45         struct list_head *list;
46
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
54 /*
55  * Setup and invoke a run of 'trigger_softirq' on the given cpu.
56  */
57 static int raise_blk_irq(int cpu, struct request *rq)
58 {
59         if (cpu_online(cpu)) {
60                 call_single_data_t *data = &rq->csd;
61
62                 data->func = trigger_softirq;
63                 data->info = rq;
64                 data->flags = 0;
65
66                 smp_call_function_single_async(cpu, data);
67                 return 0;
68         }
69
70         return 1;
71 }
72 #else /* CONFIG_SMP */
73 static int raise_blk_irq(int cpu, struct request *rq)
74 {
75         return 1;
76 }
77 #endif
78
79 static int blk_softirq_cpu_dead(unsigned int cpu)
80 {
81         /*
82          * If a CPU goes away, splice its entries to the current CPU
83          * and trigger a run of the softirq
84          */
85         local_irq_disable();
86         list_splice_init(&per_cpu(blk_cpu_done, cpu),
87                          this_cpu_ptr(&blk_cpu_done));
88         raise_softirq_irqoff(BLOCK_SOFTIRQ);
89         local_irq_enable();
90
91         return 0;
92 }
93
94 void __blk_complete_request(struct request *req)
95 {
96         struct request_queue *q = req->q;
97         int cpu, ccpu = req->mq_ctx->cpu;
98         unsigned long flags;
99         bool shared = false;
100
101         BUG_ON(!q->mq_ops->complete);
102
103         local_irq_save(flags);
104         cpu = smp_processor_id();
105
106         /*
107          * Select completion CPU
108          */
109         if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && ccpu != -1) {
110                 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
111                         shared = cpus_share_cache(cpu, ccpu);
112         } else
113                 ccpu = cpu;
114
115         /*
116          * If current CPU and requested CPU share a cache, run the softirq on
117          * the current CPU. One might concern this is just like
118          * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
119          * running in interrupt handler, and currently I/O controller doesn't
120          * support multiple interrupts, so current CPU is unique actually. This
121          * avoids IPI sending from current CPU to the first CPU of a group.
122          */
123         if (ccpu == cpu || shared) {
124                 struct list_head *list;
125 do_local:
126                 list = this_cpu_ptr(&blk_cpu_done);
127                 list_add_tail(&req->ipi_list, list);
128
129                 /*
130                  * if the list only contains our just added request,
131                  * signal a raise of the softirq. If there are already
132                  * entries there, someone already raised the irq but it
133                  * hasn't run yet.
134                  */
135                 if (list->next == &req->ipi_list)
136                         raise_softirq_irqoff(BLOCK_SOFTIRQ);
137         } else if (raise_blk_irq(ccpu, req))
138                 goto do_local;
139
140         local_irq_restore(flags);
141 }
142
143 static __init int blk_softirq_init(void)
144 {
145         int i;
146
147         for_each_possible_cpu(i)
148                 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
149
150         open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
151         cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
152                                   "block/softirq:dead", NULL,
153                                   blk_softirq_cpu_dead);
154         return 0;
155 }
156 subsys_initcall(blk_softirq_init);