tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
15static 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 */
21static __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
40static 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 */
59static 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 */
75static int raise_blk_irq(int cpu, struct request *rq)
76{
77 return 1;
78}
79#endif
80
81static 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
96void __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;
128do_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 **/
157void 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}
164EXPORT_SYMBOL(blk_complete_request);
165
166static __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}
179subsys_initcall(blk_softirq_init);