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