Linux 4.6-rc6
[cris-mirror.git] / block / blk-softirq.c
blob53b1737e978d584878f3dae13352e17a8aed1f06
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>
13 #include "blk.h"
15 static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
18 * Softirq action handler - move entries to local list and loop over them
19 * while passing them to the queue registered handler.
21 static void blk_done_softirq(struct softirq_action *h)
23 struct list_head *cpu_list, local_list;
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();
30 while (!list_empty(&local_list)) {
31 struct request *rq;
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);
39 #ifdef CONFIG_SMP
40 static void trigger_softirq(void *data)
42 struct request *rq = data;
43 unsigned long flags;
44 struct list_head *list;
46 local_irq_save(flags);
47 list = this_cpu_ptr(&blk_cpu_done);
48 list_add_tail(&rq->ipi_list, list);
50 if (list->next == &rq->ipi_list)
51 raise_softirq_irqoff(BLOCK_SOFTIRQ);
53 local_irq_restore(flags);
57 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
59 static int raise_blk_irq(int cpu, struct request *rq)
61 if (cpu_online(cpu)) {
62 struct call_single_data *data = &rq->csd;
64 data->func = trigger_softirq;
65 data->info = rq;
66 data->flags = 0;
68 smp_call_function_single_async(cpu, data);
69 return 0;
72 return 1;
74 #else /* CONFIG_SMP */
75 static int raise_blk_irq(int cpu, struct request *rq)
77 return 1;
79 #endif
81 static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
82 void *hcpu)
85 * If a CPU goes away, splice its entries to the current CPU
86 * and trigger a run of the softirq
88 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
89 int cpu = (unsigned long) hcpu;
91 local_irq_disable();
92 list_splice_init(&per_cpu(blk_cpu_done, cpu),
93 this_cpu_ptr(&blk_cpu_done));
94 raise_softirq_irqoff(BLOCK_SOFTIRQ);
95 local_irq_enable();
98 return NOTIFY_OK;
101 static struct notifier_block blk_cpu_notifier = {
102 .notifier_call = blk_cpu_notify,
105 void __blk_complete_request(struct request *req)
107 int ccpu, cpu;
108 struct request_queue *q = req->q;
109 unsigned long flags;
110 bool shared = false;
112 BUG_ON(!q->softirq_done_fn);
114 local_irq_save(flags);
115 cpu = smp_processor_id();
118 * Select completion CPU
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;
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.
135 if (ccpu == cpu || shared) {
136 struct list_head *list;
137 do_local:
138 list = this_cpu_ptr(&blk_cpu_done);
139 list_add_tail(&req->ipi_list, list);
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.
147 if (list->next == &req->ipi_list)
148 raise_softirq_irqoff(BLOCK_SOFTIRQ);
149 } else if (raise_blk_irq(ccpu, req))
150 goto do_local;
152 local_irq_restore(flags);
156 * blk_complete_request - end I/O on a request
157 * @req: the request being processed
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().
166 void blk_complete_request(struct request *req)
168 if (unlikely(blk_should_fake_timeout(req->q)))
169 return;
170 if (!blk_mark_rq_complete(req))
171 __blk_complete_request(req);
173 EXPORT_SYMBOL(blk_complete_request);
175 static __init int blk_softirq_init(void)
177 int i;
179 for_each_possible_cpu(i)
180 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
182 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
183 register_hotcpu_notifier(&blk_cpu_notifier);
184 return 0;
186 subsys_initcall(blk_softirq_init);