/* * Functions related to softirq rq completions */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/bio.h> #include <linux/blkdev.h> #include <linux/interrupt.h> #include <linux/cpu.h> #include <linux/sched.h> #include "blk.h" static DEFINE_PER_CPU(struct list_head, blk_cpu_done); /* * Softirq action handler - move entries to local list and loop over them * while passing them to the queue registered handler. */ static void blk_done_softirq(struct softirq_action *h) { struct list_head *cpu_list, local_list; local_irq_disable(); cpu_list = this_cpu_ptr(&blk_cpu_done); list_replace_init(cpu_list, &local_list); local_irq_enable(); while (!list_empty(&local_list)) { struct request *rq; rq = list_entry(local_list.next, struct request, csd.list); list_del_init(&rq->csd.list); rq->q->softirq_done_fn(rq); } } #if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS) static void trigger_softirq(void *data) { struct request *rq = data; unsigned long flags; struct list_head *list; local_irq_save(flags); list = this_cpu_ptr(&blk_cpu_done); list_add_tail(&rq->csd.list, list); if (list->next == &rq->csd.list) raise_softirq_irqoff(BLOCK_SOFTIRQ); local_irq_restore(flags); } /* * Setup and invoke a run of 'trigger_softirq' on the given cpu. */ static int raise_blk_irq(int cpu, struct request *rq) { if (cpu_online(cpu)) { struct call_single_data *data = &rq->csd; data->func = trigger_softirq; data->info = rq; data->flags = 0; __smp_call_function_single(cpu, data, 0); return 0; } return 1; } #else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */ static int raise_blk_irq(int cpu, struct request *rq) { return 1; } #endif static int blk_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { /* * If a CPU goes away, splice its entries to the current CPU * and trigger a run of the softirq */ if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { int cpu = (unsigned long) hcpu; local_irq_disable(); list_splice_init(&per_cpu(blk_cpu_done, cpu), this_cpu_ptr(&blk_cpu_done)); raise_softirq_irqoff(BLOCK_SOFTIRQ); local_irq_enable(); } return NOTIFY_OK; } static struct notifier_block blk_cpu_notifier = { .notifier_call = blk_cpu_notify, }; void __blk_complete_request(struct request *req) { int ccpu, cpu; struct request_queue *q = req->q; unsigned long flags; bool shared = false; BUG_ON(!q->softirq_done_fn); local_irq_save(flags); cpu = smp_processor_id(); /* * Select completion CPU */ if (req->cpu != -1) { ccpu = req->cpu; if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) shared = cpus_share_cache(cpu, ccpu); } else ccpu = cpu; /* * If current CPU and requested CPU share a cache, run the softirq on * the current CPU. One might concern this is just like * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is * running in interrupt handler, and currently I/O controller doesn't * support multiple interrupts, so current CPU is unique actually. This * avoids IPI sending from current CPU to the first CPU of a group. */ if (ccpu == cpu || shared) { struct list_head *list; do_local: list = this_cpu_ptr(&blk_cpu_done); list_add_tail(&req->csd.list, list); /* * if the list only contains our just added request, * signal a raise of the softirq. If there are already * entries there, someone already raised the irq but it * hasn't run yet. */ if (list->next == &req->csd.list) raise_softirq_irqoff(BLOCK_SOFTIRQ); } else if (raise_blk_irq(ccpu, req)) goto do_local; local_irq_restore(flags); } /** * blk_complete_request - end I/O on a request * @req: the request being processed * * Description: * Ends all I/O on a request. It does not handle partial completions, * unless the driver actually implements this in its completion callback * through requeueing. The actual completion happens out-of-order, * through a softirq handler. The user must have registered a completion * callback through blk_queue_softirq_done(). **/ void blk_complete_request(struct request *req) { if (unlikely(blk_should_fake_timeout(req->q))) return; if (!blk_mark_rq_complete(req)) __blk_complete_request(req); } EXPORT_SYMBOL(blk_complete_request); static __init int blk_softirq_init(void) { int i; for_each_possible_cpu(i) INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); register_hotcpu_notifier(&blk_cpu_notifier); return 0; } subsys_initcall(blk_softirq_init);