[deliverable/linux.git] / block / blk-softirq.c

/*
 * 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 = &__get_cpu_var(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 = &__get_cpu_var(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 __cpuinit 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),
				 &__get_cpu_var(blk_cpu_done));
		raise_softirq_irqoff(BLOCK_SOFTIRQ);
		local_irq_enable();
	}

	return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata 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 = &__get_cpu_var(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);
Commit	Line	Data
b646fc59 JA	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>
39be3501	11	#include <linux/sched.h>
b646fc59 JA	12
	13	#include "blk.h"
	14
	15	static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
	16
c7c22e4d JA	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 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 = &__get_cpu_var(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, csd.list);
	34	list_del_init(&rq->csd.list);
	35	rq->q->softirq_done_fn(rq);
	36	}
	37	}
	38
	39	#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)
	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 = &__get_cpu_var(blk_cpu_done);
	48	list_add_tail(&rq->csd.list, list);
	49
	50	if (list->next == &rq->csd.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
6e275637	68	__smp_call_function_single(cpu, data, 0);
c7c22e4d JA	69	return 0;
	70	}
	71
	72	return 1;
	73	}
	74	#else /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */
	75	static int raise_blk_irq(int cpu, struct request *rq)
	76	{
	77	return 1;
	78	}
	79	#endif
	80
b646fc59 JA	81	static int __cpuinit blk_cpu_notify(struct notifier_block *self,
	82	unsigned long action, void *hcpu)
	83	{
	84	/*
	85	* If a CPU goes away, splice its entries to the current CPU
	86	* and trigger a run of the softirq
	87	*/
	88	if (action == CPU_DEAD \|\| action == CPU_DEAD_FROZEN) {
	89	int cpu = (unsigned long) hcpu;
	90
	91	local_irq_disable();
	92	list_splice_init(&per_cpu(blk_cpu_done, cpu),
	93	&__get_cpu_var(blk_cpu_done));
	94	raise_softirq_irqoff(BLOCK_SOFTIRQ);
	95	local_irq_enable();
	96	}
	97
	98	return NOTIFY_OK;
	99	}
	100
c7c22e4d	101	static struct notifier_block __cpuinitdata blk_cpu_notifier = {
b646fc59 JA	102	.notifier_call = blk_cpu_notify,
	103	};
	104
242f9dcb	105	void __blk_complete_request(struct request *req)
b646fc59	106	{
39be3501	107	int ccpu, cpu;
c7c22e4d	108	struct request_queue *q = req->q;
b646fc59	109	unsigned long flags;
39be3501	110	bool shared = false;
b646fc59	111
c7c22e4d	112	BUG_ON(!q->softirq_done_fn);
b646fc59 JA	113
b646fc59 JA	114	local_irq_save(flags);
c7c22e4d	115	cpu = smp_processor_id();
b646fc59	116
c7c22e4d JA	117	/*
	118	* Select completion CPU
	119	*/
8ad6a56f	120	if (req->cpu != -1) {
c7c22e4d	121	ccpu = req->cpu;
39be3501 PZ	122	if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
39be3501 PZ	123	shared = cpus_share_cache(cpu, ccpu);
5757a6d7	124	} else
c7c22e4d JA	125	ccpu = cpu;
c7c22e4d JA	126
bcf30e75	127	/*
39be3501 PZ	128	* If current CPU and requested CPU share a cache, run the softirq on
39be3501 PZ	129	* the current CPU. One might concern this is just like
bcf30e75 SL	130	* QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
	131	* running in interrupt handler, and currently I/O controller doesn't
	132	* support multiple interrupts, so current CPU is unique actually. This
	133	* avoids IPI sending from current CPU to the first CPU of a group.
	134	*/
39be3501	135	if (ccpu == cpu \|\| shared) {
c7c22e4d JA	136	struct list_head *list;
	137	do_local:
	138	list = &__get_cpu_var(blk_cpu_done);
	139	list_add_tail(&req->csd.list, list);
	140
	141	/*
	142	* if the list only contains our just added request,
	143	* signal a raise of the softirq. If there are already
	144	* entries there, someone already raised the irq but it
	145	* hasn't run yet.
	146	*/
	147	if (list->next == &req->csd.list)
	148	raise_softirq_irqoff(BLOCK_SOFTIRQ);
	149	} else if (raise_blk_irq(ccpu, req))
	150	goto do_local;
b646fc59 JA	151
	152	local_irq_restore(flags);
	153	}
242f9dcb JA	154
	155	/**
	156	* blk_complete_request - end I/O on a request
	157	* @req: the request being processed
	158	*
	159	* Description:
	160	* Ends all I/O on a request. It does not handle partial completions,
	161	* unless the driver actually implements this in its completion callback
	162	* through requeueing. The actual completion happens out-of-order,
	163	* through a softirq handler. The user must have registered a completion
	164	* callback through blk_queue_softirq_done().
	165	**/
	166	void blk_complete_request(struct request *req)
	167	{
581d4e28 JA	168	if (unlikely(blk_should_fake_timeout(req->q)))
581d4e28 JA	169	return;
242f9dcb JA	170	if (!blk_mark_rq_complete(req))
	171	__blk_complete_request(req);
	172	}
b646fc59 JA	173	EXPORT_SYMBOL(blk_complete_request);
b646fc59 JA	174
3c18ce71	175	static __init int blk_softirq_init(void)
b646fc59 JA	176	{
	177	int i;
	178
	179	for_each_possible_cpu(i)
	180	INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
	181
	182	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
	183	register_hotcpu_notifier(&blk_cpu_notifier);
	184	return 0;
	185	}
	186	subsys_initcall(blk_softirq_init);