Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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
17static 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 */
23static __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
42static 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 */
57static 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 */
73static int raise_blk_irq(int cpu, struct request *rq)
74{
75 return 1;
76}
77#endif
78
79static 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
94void __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;
125do_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
143static __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}
156subsys_initcall(blk_softirq_init);