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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 | |
| 12 | #include "blk.h" |
| 13 | |
| 14 | static DEFINE_PER_CPU(struct list_head, blk_cpu_done); |
| 15 | |
| 16 | /* |
| 17 | * Softirq action handler - move entries to local list and loop over them |
| 18 | * while passing them to the queue registered handler. |
| 19 | */ |
| 20 | static void blk_done_softirq(struct softirq_action *h) |
| 21 | { |
| 22 | struct list_head *cpu_list, local_list; |
| 23 | |
| 24 | local_irq_disable(); |
| 25 | cpu_list = &__get_cpu_var(blk_cpu_done); |
| 26 | list_replace_init(cpu_list, &local_list); |
| 27 | local_irq_enable(); |
| 28 | |
| 29 | while (!list_empty(&local_list)) { |
| 30 | struct request *rq; |
| 31 | |
| 32 | rq = list_entry(local_list.next, struct request, csd.list); |
| 33 | list_del_init(&rq->csd.list); |
| 34 | rq->q->softirq_done_fn(rq); |
| 35 | } |
| 36 | } |
| 37 | |
| 38 | #if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS) |
| 39 | static void trigger_softirq(void *data) |
| 40 | { |
| 41 | struct request *rq = data; |
| 42 | unsigned long flags; |
| 43 | struct list_head *list; |
| 44 | |
| 45 | local_irq_save(flags); |
| 46 | list = &__get_cpu_var(blk_cpu_done); |
| 47 | list_add_tail(&rq->csd.list, list); |
| 48 | |
| 49 | if (list->next == &rq->csd.list) |
| 50 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
| 51 | |
| 52 | local_irq_restore(flags); |
| 53 | } |
| 54 | |
| 55 | /* |
| 56 | * Setup and invoke a run of 'trigger_softirq' on the given cpu. |
| 57 | */ |
| 58 | static int raise_blk_irq(int cpu, struct request *rq) |
| 59 | { |
| 60 | if (cpu_online(cpu)) { |
| 61 | struct call_single_data *data = &rq->csd; |
| 62 | |
| 63 | data->func = trigger_softirq; |
| 64 | data->info = rq; |
| 65 | data->flags = 0; |
| 66 | |
| 67 | __smp_call_function_single(cpu, data, 0); |
| 68 | return 0; |
| 69 | } |
| 70 | |
| 71 | return 1; |
| 72 | } |
| 73 | #else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */ |
| 74 | static int raise_blk_irq(int cpu, struct request *rq) |
| 75 | { |
| 76 | return 1; |
| 77 | } |
| 78 | #endif |
| 79 | |
| 80 | static int __cpuinit blk_cpu_notify(struct notifier_block *self, |
| 81 | unsigned long action, void *hcpu) |
| 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 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { |
| 88 | int cpu = (unsigned long) hcpu; |
| 89 | |
| 90 | local_irq_disable(); |
| 91 | list_splice_init(&per_cpu(blk_cpu_done, cpu), |
| 92 | &__get_cpu_var(blk_cpu_done)); |
| 93 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
| 94 | local_irq_enable(); |
| 95 | } |
| 96 | |
| 97 | return NOTIFY_OK; |
| 98 | } |
| 99 | |
| 100 | static struct notifier_block __cpuinitdata blk_cpu_notifier = { |
| 101 | .notifier_call = blk_cpu_notify, |
| 102 | }; |
| 103 | |
| 104 | void __blk_complete_request(struct request *req) |
| 105 | { |
| 106 | struct request_queue *q = req->q; |
| 107 | unsigned long flags; |
| 108 | int ccpu, cpu, group_cpu; |
| 109 | |
| 110 | BUG_ON(!q->softirq_done_fn); |
| 111 | |
| 112 | local_irq_save(flags); |
| 113 | cpu = smp_processor_id(); |
| 114 | group_cpu = blk_cpu_to_group(cpu); |
| 115 | |
| 116 | /* |
| 117 | * Select completion CPU |
| 118 | */ |
| 119 | if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && req->cpu != -1) |
| 120 | ccpu = req->cpu; |
| 121 | else |
| 122 | ccpu = cpu; |
| 123 | |
| 124 | if (ccpu == cpu || ccpu == group_cpu) { |
| 125 | struct list_head *list; |
| 126 | do_local: |
| 127 | list = &__get_cpu_var(blk_cpu_done); |
| 128 | list_add_tail(&req->csd.list, list); |
| 129 | |
| 130 | /* |
| 131 | * if the list only contains our just added request, |
| 132 | * signal a raise of the softirq. If there are already |
| 133 | * entries there, someone already raised the irq but it |
| 134 | * hasn't run yet. |
| 135 | */ |
| 136 | if (list->next == &req->csd.list) |
| 137 | raise_softirq_irqoff(BLOCK_SOFTIRQ); |
| 138 | } else if (raise_blk_irq(ccpu, req)) |
| 139 | goto do_local; |
| 140 | |
| 141 | local_irq_restore(flags); |
| 142 | } |
| 143 | |
| 144 | /** |
| 145 | * blk_complete_request - end I/O on a request |
| 146 | * @req: the request being processed |
| 147 | * |
| 148 | * Description: |
| 149 | * Ends all I/O on a request. It does not handle partial completions, |
| 150 | * unless the driver actually implements this in its completion callback |
| 151 | * through requeueing. The actual completion happens out-of-order, |
| 152 | * through a softirq handler. The user must have registered a completion |
| 153 | * callback through blk_queue_softirq_done(). |
| 154 | **/ |
| 155 | void blk_complete_request(struct request *req) |
| 156 | { |
| 157 | if (unlikely(blk_should_fake_timeout(req->q))) |
| 158 | return; |
| 159 | if (!blk_mark_rq_complete(req)) |
| 160 | __blk_complete_request(req); |
| 161 | } |
| 162 | EXPORT_SYMBOL(blk_complete_request); |
| 163 | |
| 164 | static __init int blk_softirq_init(void) |
| 165 | { |
| 166 | int i; |
| 167 | |
| 168 | for_each_possible_cpu(i) |
| 169 | INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); |
| 170 | |
| 171 | open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); |
| 172 | register_hotcpu_notifier(&blk_cpu_notifier); |
| 173 | return 0; |
| 174 | } |
| 175 | subsys_initcall(blk_softirq_init); |
| 176 |
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