// SPDX-License-Identifier: GPL-2.0/* * Functions related to interrupt-poll handling in the block layer. This * is similar to NAPI for network devices. */#include <linux/kernel.h>#include <linux/module.h>#include <linux/init.h>#include <linux/bio.h>#include <linux/interrupt.h>#include <linux/cpu.h>#include <linux/irq_poll.h>#include <linux/delay.h> static unsigned int irq_poll_budget __read_mostly = 256; static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll); /** * irq_poll_sched - Schedule a run of the iopoll handler * @iop:      The parent iopoll structure * * Description: *     Add this irq_poll structure to the pending poll list and trigger the *     raise of the blk iopoll softirq. **/void irq_poll_sched(struct irq_poll *iop){	unsigned long flags; 	if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))		return;	if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))		return; 	local_irq_save(flags);	list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));	raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);	local_irq_restore(flags);}EXPORT_SYMBOL(irq_poll_sched); /** * __irq_poll_complete - Mark this @iop as un-polled again * @iop:      The parent iopoll structure * * Description: *     See irq_poll_complete(). This function must be called with interrupts *     disabled. **/static void __irq_poll_complete(struct irq_poll *iop){	list_del(&iop->list);	smp_mb__before_atomic();	clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);} /** * irq_poll_complete - Mark this @iop as un-polled again * @iop:      The parent iopoll structure * * Description: *     If a driver consumes less than the assigned budget in its run of the *     iopoll handler, it'll end the polled mode by calling this function. The *     iopoll handler will not be invoked again before irq_poll_sched() *     is called. **/void irq_poll_complete(struct irq_poll *iop){	unsigned long flags; 	local_irq_save(flags);	__irq_poll_complete(iop);	local_irq_restore(flags);}EXPORT_SYMBOL(irq_poll_complete); static void __latent_entropy irq_poll_softirq(void){	struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);	int rearm = 0, budget = irq_poll_budget;	unsigned long start_time = jiffies; 	local_irq_disable(); 	while (!list_empty(list)) {		struct irq_poll *iop;		int work, weight; 		/*		 * If softirq window is exhausted then punt.		 */		if (budget <= 0 || time_after(jiffies, start_time)) {			rearm = 1;			break;		} 		local_irq_enable(); 		/* Even though interrupts have been re-enabled, this		 * access is safe because interrupts can only add new		 * entries to the tail of this list, and only ->poll()		 * calls can remove this head entry from the list.		 */		iop = list_entry(list->next, struct irq_poll, list); 		weight = iop->weight;		work = 0;		if (test_bit(IRQ_POLL_F_SCHED, &iop->state))			work = iop->poll(iop, weight); 		budget -= work; 		local_irq_disable(); 		/*		 * Drivers must not modify the iopoll state, if they		 * consume their assigned weight (or more, some drivers can't		 * easily just stop processing, they have to complete an		 * entire mask of commands).In such cases this code		 * still "owns" the iopoll instance and therefore can		 * move the instance around on the list at-will.		 */		if (work >= weight) {			if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))				__irq_poll_complete(iop);			else				list_move_tail(&iop->list, list);		}	} 	if (rearm)		__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ); 	local_irq_enable();} /** * irq_poll_disable - Disable iopoll on this @iop * @iop:      The parent iopoll structure * * Description: *     Disable io polling and wait for any pending callbacks to have completed. **/void irq_poll_disable(struct irq_poll *iop){	set_bit(IRQ_POLL_F_DISABLE, &iop->state);	while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))		msleep(1);	clear_bit(IRQ_POLL_F_DISABLE, &iop->state);}EXPORT_SYMBOL(irq_poll_disable); /** * irq_poll_enable - Enable iopoll on this @iop * @iop:      The parent iopoll structure * * Description: *     Enable iopoll on this @iop. Note that the handler run will not be *     scheduled, it will only mark it as active. **/void irq_poll_enable(struct irq_poll *iop){	BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));	smp_mb__before_atomic();	clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);}EXPORT_SYMBOL(irq_poll_enable); /** * irq_poll_init - Initialize this @iop * @iop:      The parent iopoll structure * @weight:   The default weight (or command completion budget) * @poll_fn:  The handler to invoke * * Description: *     Initialize and enable this irq_poll structure. **/void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn){	memset(iop, 0, sizeof(*iop));	INIT_LIST_HEAD(&iop->list);	iop->weight = weight;	iop->poll = poll_fn;}EXPORT_SYMBOL(irq_poll_init); static int irq_poll_cpu_dead(unsigned int cpu){	/*	 * If a CPU goes away, splice its entries to the current CPU and	 * set the POLL softirq bit. The local_bh_disable()/enable() pair	 * ensures that it is handled. Otherwise the current CPU could	 * reach idle with the POLL softirq pending.	 */	local_bh_disable();	local_irq_disable();	list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),			 this_cpu_ptr(&blk_cpu_iopoll));	__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);	local_irq_enable();	local_bh_enable(); 	return 0;} static __init int irq_poll_setup(void){	int i; 	for_each_possible_cpu(i)		INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i)); 	open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq);	cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL,				  irq_poll_cpu_dead);	return 0;}subsys_initcall(irq_poll_setup);