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/*
* 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, queuelist);
list_del_init(&rq->queuelist);
rq->q->softirq_done_fn(rq);
}
}
#ifdef CONFIG_SMP
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);
/*
* We reuse queuelist for a list of requests to process. Since the
* queuelist is used by the block layer only for requests waiting to be
* submitted to the device it is unused now.
*/
list_add_tail(&rq->queuelist, list);
if (list->next == &rq->queuelist)
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 */
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->queuelist, 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->queuelist)
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);
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