Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/block/blk-softirq.c

  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 __latent_entropy 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, ipi_list);
 34                 list_del_init(&rq->ipi_list);
 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         list_add_tail(&rq->ipi_list, list);
 49 
 50         if (list->next == &rq->ipi_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  */
 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_async(cpu, data);
 69                 return 0;
 70         }
 71 
 72         return 1;
 73 }
 74 #else /* CONFIG_SMP */
 75 static int raise_blk_irq(int cpu, struct request *rq)
 76 {
 77         return 1;
 78 }
 79 #endif
 80 
 81 static int blk_softirq_cpu_dead(unsigned int cpu)
 82 {
 83         /*
 84          * If a CPU goes away, splice its entries to the current CPU
 85          * and trigger a run of the softirq
 86          */
 87         local_irq_disable();
 88         list_splice_init(&per_cpu(blk_cpu_done, cpu),
 89                          this_cpu_ptr(&blk_cpu_done));
 90         raise_softirq_irqoff(BLOCK_SOFTIRQ);
 91         local_irq_enable();
 92 
 93         return 0;
 94 }
 95 
 96 void __blk_complete_request(struct request *req)
 97 {
 98         int ccpu, cpu;
 99         struct request_queue *q = req->q;
100         unsigned long flags;
101         bool shared = false;
102 
103         BUG_ON(!q->softirq_done_fn);
104 
105         local_irq_save(flags);
106         cpu = smp_processor_id();
107 
108         /*
109          * Select completion CPU
110          */
111         if (req->cpu != -1) {
112                 ccpu = req->cpu;
113                 if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
114                         shared = cpus_share_cache(cpu, ccpu);
115         } else
116                 ccpu = cpu;
117 
118         /*
119          * If current CPU and requested CPU share a cache, run the softirq on
120          * the current CPU. One might concern this is just like
121          * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
122          * running in interrupt handler, and currently I/O controller doesn't
123          * support multiple interrupts, so current CPU is unique actually. This
124          * avoids IPI sending from current CPU to the first CPU of a group.
125          */
126         if (ccpu == cpu || shared) {
127                 struct list_head *list;
128 do_local:
129                 list = this_cpu_ptr(&blk_cpu_done);
130                 list_add_tail(&req->ipi_list, list);
131 
132                 /*
133                  * if the list only contains our just added request,
134                  * signal a raise of the softirq. If there are already
135                  * entries there, someone already raised the irq but it
136                  * hasn't run yet.
137                  */
138                 if (list->next == &req->ipi_list)
139                         raise_softirq_irqoff(BLOCK_SOFTIRQ);
140         } else if (raise_blk_irq(ccpu, req))
141                 goto do_local;
142 
143         local_irq_restore(flags);
144 }
145 
146 /**
147  * blk_complete_request - end I/O on a request
148  * @req:      the request being processed
149  *
150  * Description:
151  *     Ends all I/O on a request. It does not handle partial completions,
152  *     unless the driver actually implements this in its completion callback
153  *     through requeueing. The actual completion happens out-of-order,
154  *     through a softirq handler. The user must have registered a completion
155  *     callback through blk_queue_softirq_done().
156  **/
157 void blk_complete_request(struct request *req)
158 {
159         if (unlikely(blk_should_fake_timeout(req->q)))
160                 return;
161         if (!blk_mark_rq_complete(req))
162                 __blk_complete_request(req);
163 }
164 EXPORT_SYMBOL(blk_complete_request);
165 
166 static __init int blk_softirq_init(void)
167 {
168         int i;
169 
170         for_each_possible_cpu(i)
171                 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
172 
173         open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
174         cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
175                                   "block/softirq:dead", NULL,
176                                   blk_softirq_cpu_dead);
177         return 0;
178 }
179 subsys_initcall(blk_softirq_init);
180 

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us