2 * Functions related to softirq rq completions
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
8 #include <linux/blkdev.h>
9 #include <linux/interrupt.h>
10 #include <linux/cpu.h>
11 #include <linux/sched.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;
26 cpu_list = this_cpu_ptr(&blk_cpu_done);
27 list_replace_init(cpu_list, &local_list);
30 while (!list_empty(&local_list)) {
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);
40 static void trigger_softirq(void *data)
42 struct request *rq = data;
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);
54 preempt_check_resched_rt();
58 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
60 static int raise_blk_irq(int cpu, struct request *rq)
62 if (cpu_online(cpu)) {
63 struct call_single_data *data = &rq->csd;
65 data->func = trigger_softirq;
69 smp_call_function_single_async(cpu, data);
75 #else /* CONFIG_SMP */
76 static int raise_blk_irq(int cpu, struct request *rq)
82 static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
86 * If a CPU goes away, splice its entries to the current CPU
87 * and trigger a run of the softirq
89 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
90 int cpu = (unsigned long) hcpu;
93 list_splice_init(&per_cpu(blk_cpu_done, cpu),
94 this_cpu_ptr(&blk_cpu_done));
95 raise_softirq_irqoff(BLOCK_SOFTIRQ);
97 preempt_check_resched_rt();
103 static struct notifier_block blk_cpu_notifier = {
104 .notifier_call = blk_cpu_notify,
107 void __blk_complete_request(struct request *req)
110 struct request_queue *q = req->q;
114 BUG_ON(!q->softirq_done_fn);
116 local_irq_save(flags);
117 cpu = smp_processor_id();
120 * Select completion CPU
122 if (req->cpu != -1) {
124 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
125 shared = cpus_share_cache(cpu, ccpu);
130 * If current CPU and requested CPU share a cache, run the softirq on
131 * the current CPU. One might concern this is just like
132 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
133 * running in interrupt handler, and currently I/O controller doesn't
134 * support multiple interrupts, so current CPU is unique actually. This
135 * avoids IPI sending from current CPU to the first CPU of a group.
137 if (ccpu == cpu || shared) {
138 struct list_head *list;
140 list = this_cpu_ptr(&blk_cpu_done);
141 list_add_tail(&req->ipi_list, list);
144 * if the list only contains our just added request,
145 * signal a raise of the softirq. If there are already
146 * entries there, someone already raised the irq but it
149 if (list->next == &req->ipi_list)
150 raise_softirq_irqoff(BLOCK_SOFTIRQ);
151 } else if (raise_blk_irq(ccpu, req))
154 local_irq_restore(flags);
155 preempt_check_resched_rt();
159 * blk_complete_request - end I/O on a request
160 * @req: the request being processed
163 * Ends all I/O on a request. It does not handle partial completions,
164 * unless the driver actually implements this in its completion callback
165 * through requeueing. The actual completion happens out-of-order,
166 * through a softirq handler. The user must have registered a completion
167 * callback through blk_queue_softirq_done().
169 void blk_complete_request(struct request *req)
171 if (unlikely(blk_should_fake_timeout(req->q)))
173 if (!blk_mark_rq_complete(req))
174 __blk_complete_request(req);
176 EXPORT_SYMBOL(blk_complete_request);
178 static __init int blk_softirq_init(void)
182 for_each_possible_cpu(i)
183 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
185 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
186 register_hotcpu_notifier(&blk_cpu_notifier);
189 subsys_initcall(blk_softirq_init);