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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
15 static 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 */
21 static 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, queuelist);
34 list_del_init(&rq->queuelist);
35 rq->q->softirq_done_fn(rq);
36 }
37 }
38
39 #ifdef CONFIG_SMP
40 static 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 /*
49 * We reuse queuelist for a list of requests to process. Since the
50 * queuelist is used by the block layer only for requests waiting to be
51 * submitted to the device it is unused now.
52 */
53 list_add_tail(&rq->queuelist, list);
54
55 if (list->next == &rq->queuelist)
56 raise_softirq_irqoff(BLOCK_SOFTIRQ);
57
58 local_irq_restore(flags);
59 }
60
61 /*
62 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
63 */
64 static int raise_blk_irq(int cpu, struct request *rq)
65 {
66 if (cpu_online(cpu)) {
67 struct call_single_data *data = &rq->csd;
68
69 data->func = trigger_softirq;
70 data->info = rq;
71 data->flags = 0;
72
73 smp_call_function_single_async(cpu, data);
74 return 0;
75 }
76
77 return 1;
78 }
79 #else /* CONFIG_SMP */
80 static int raise_blk_irq(int cpu, struct request *rq)
81 {
82 return 1;
83 }
84 #endif
85
86 static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
87 void *hcpu)
88 {
89 /*
90 * If a CPU goes away, splice its entries to the current CPU
91 * and trigger a run of the softirq
92 */
93 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
94 int cpu = (unsigned long) hcpu;
95
96 local_irq_disable();
97 list_splice_init(&per_cpu(blk_cpu_done, cpu),
98 this_cpu_ptr(&blk_cpu_done));
99 raise_softirq_irqoff(BLOCK_SOFTIRQ);
100 local_irq_enable();
101 }
102
103 return NOTIFY_OK;
104 }
105
106 static struct notifier_block blk_cpu_notifier = {
107 .notifier_call = blk_cpu_notify,
108 };
109
110 void __blk_complete_request(struct request *req)
111 {
112 int ccpu, cpu;
113 struct request_queue *q = req->q;
114 unsigned long flags;
115 bool shared = false;
116
117 BUG_ON(!q->softirq_done_fn);
118
119 local_irq_save(flags);
120 cpu = smp_processor_id();
121
122 /*
123 * Select completion CPU
124 */
125 if (req->cpu != -1) {
126 ccpu = req->cpu;
127 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
128 shared = cpus_share_cache(cpu, ccpu);
129 } else
130 ccpu = cpu;
131
132 /*
133 * If current CPU and requested CPU share a cache, run the softirq on
134 * the current CPU. One might concern this is just like
135 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
136 * running in interrupt handler, and currently I/O controller doesn't
137 * support multiple interrupts, so current CPU is unique actually. This
138 * avoids IPI sending from current CPU to the first CPU of a group.
139 */
140 if (ccpu == cpu || shared) {
141 struct list_head *list;
142 do_local:
143 list = this_cpu_ptr(&blk_cpu_done);
144 list_add_tail(&req->queuelist, list);
145
146 /*
147 * if the list only contains our just added request,
148 * signal a raise of the softirq. If there are already
149 * entries there, someone already raised the irq but it
150 * hasn't run yet.
151 */
152 if (list->next == &req->queuelist)
153 raise_softirq_irqoff(BLOCK_SOFTIRQ);
154 } else if (raise_blk_irq(ccpu, req))
155 goto do_local;
156
157 local_irq_restore(flags);
158 }
159
160 /**
161 * blk_complete_request - end I/O on a request
162 * @req: the request being processed
163 *
164 * Description:
165 * Ends all I/O on a request. It does not handle partial completions,
166 * unless the driver actually implements this in its completion callback
167 * through requeueing. The actual completion happens out-of-order,
168 * through a softirq handler. The user must have registered a completion
169 * callback through blk_queue_softirq_done().
170 **/
171 void blk_complete_request(struct request *req)
172 {
173 if (unlikely(blk_should_fake_timeout(req->q)))
174 return;
175 if (!blk_mark_rq_complete(req))
176 __blk_complete_request(req);
177 }
178 EXPORT_SYMBOL(blk_complete_request);
179
180 static __init int blk_softirq_init(void)
181 {
182 int i;
183
184 for_each_possible_cpu(i)
185 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
186
187 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
188 register_hotcpu_notifier(&blk_cpu_notifier);
189 return 0;
190 }
191 subsys_initcall(blk_softirq_init);