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