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![Peter Zijlstra](/assets/img/avatar_default.png)
The block layer has some code trying to determine if two CPUs share a cache, the scheduler has a similar function. Expose the function used by the scheduler and make the block layer use it, thereby removing the block layers usage of CONFIG_SCHED* and topology bits. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jens Axboe <axboe@kernel.dk> Link: http://lkml.kernel.org/r/1327579450.2446.95.camel@twins
186 lines
4.5 KiB
C
186 lines
4.5 KiB
C
/*
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* Functions related to softirq rq completions
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/interrupt.h>
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#include <linux/cpu.h>
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#include <linux/sched.h>
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#include "blk.h"
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static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
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/*
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* Softirq action handler - move entries to local list and loop over them
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* while passing them to the queue registered handler.
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*/
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static void blk_done_softirq(struct softirq_action *h)
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{
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struct list_head *cpu_list, local_list;
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local_irq_disable();
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cpu_list = &__get_cpu_var(blk_cpu_done);
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list_replace_init(cpu_list, &local_list);
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local_irq_enable();
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while (!list_empty(&local_list)) {
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struct request *rq;
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rq = list_entry(local_list.next, struct request, csd.list);
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list_del_init(&rq->csd.list);
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rq->q->softirq_done_fn(rq);
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}
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}
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#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)
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static void trigger_softirq(void *data)
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{
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struct request *rq = data;
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unsigned long flags;
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struct list_head *list;
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local_irq_save(flags);
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list = &__get_cpu_var(blk_cpu_done);
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list_add_tail(&rq->csd.list, list);
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if (list->next == &rq->csd.list)
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raise_softirq_irqoff(BLOCK_SOFTIRQ);
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local_irq_restore(flags);
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}
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/*
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* Setup and invoke a run of 'trigger_softirq' on the given cpu.
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*/
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static int raise_blk_irq(int cpu, struct request *rq)
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{
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if (cpu_online(cpu)) {
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struct call_single_data *data = &rq->csd;
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data->func = trigger_softirq;
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data->info = rq;
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data->flags = 0;
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__smp_call_function_single(cpu, data, 0);
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return 0;
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}
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return 1;
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}
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#else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */
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static int raise_blk_irq(int cpu, struct request *rq)
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{
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return 1;
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}
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#endif
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static int __cpuinit blk_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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/*
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* If a CPU goes away, splice its entries to the current CPU
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* and trigger a run of the softirq
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*/
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if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
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int cpu = (unsigned long) hcpu;
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local_irq_disable();
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list_splice_init(&per_cpu(blk_cpu_done, cpu),
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&__get_cpu_var(blk_cpu_done));
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raise_softirq_irqoff(BLOCK_SOFTIRQ);
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local_irq_enable();
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}
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return NOTIFY_OK;
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}
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static struct notifier_block __cpuinitdata blk_cpu_notifier = {
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.notifier_call = blk_cpu_notify,
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};
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void __blk_complete_request(struct request *req)
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{
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int ccpu, cpu;
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struct request_queue *q = req->q;
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unsigned long flags;
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bool shared = false;
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BUG_ON(!q->softirq_done_fn);
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local_irq_save(flags);
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cpu = smp_processor_id();
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/*
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* Select completion CPU
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*/
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if (req->cpu != -1) {
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ccpu = req->cpu;
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if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
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shared = cpus_share_cache(cpu, ccpu);
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} else
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ccpu = cpu;
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/*
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* If current CPU and requested CPU share a cache, run the softirq on
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* the current CPU. One might concern this is just like
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* QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
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* running in interrupt handler, and currently I/O controller doesn't
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* support multiple interrupts, so current CPU is unique actually. This
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* avoids IPI sending from current CPU to the first CPU of a group.
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*/
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if (ccpu == cpu || shared) {
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struct list_head *list;
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do_local:
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list = &__get_cpu_var(blk_cpu_done);
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list_add_tail(&req->csd.list, list);
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/*
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* if the list only contains our just added request,
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* signal a raise of the softirq. If there are already
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* entries there, someone already raised the irq but it
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* hasn't run yet.
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*/
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if (list->next == &req->csd.list)
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raise_softirq_irqoff(BLOCK_SOFTIRQ);
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} else if (raise_blk_irq(ccpu, req))
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goto do_local;
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local_irq_restore(flags);
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}
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/**
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* blk_complete_request - end I/O on a request
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* @req: the request being processed
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*
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* Description:
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* Ends all I/O on a request. It does not handle partial completions,
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* unless the driver actually implements this in its completion callback
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* through requeueing. The actual completion happens out-of-order,
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* through a softirq handler. The user must have registered a completion
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* callback through blk_queue_softirq_done().
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**/
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void blk_complete_request(struct request *req)
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{
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if (unlikely(blk_should_fake_timeout(req->q)))
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return;
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if (!blk_mark_rq_complete(req))
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__blk_complete_request(req);
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}
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EXPORT_SYMBOL(blk_complete_request);
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static __init int blk_softirq_init(void)
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{
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int i;
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for_each_possible_cpu(i)
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INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
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open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
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register_hotcpu_notifier(&blk_cpu_notifier);
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return 0;
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}
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subsys_initcall(blk_softirq_init);
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