// SPDX-License-Identifier: GPL-2.0/* * <linux/swait.h> (simple wait queues ) implementation: */#include "sched.h" void __init_swait_queue_head(struct swait_queue_head *q, const char *name,			     struct lock_class_key *key){	raw_spin_lock_init(&q->lock);	lockdep_set_class_and_name(&q->lock, key, name);	INIT_LIST_HEAD(&q->task_list);}EXPORT_SYMBOL(__init_swait_queue_head); /* * The thing about the wake_up_state() return value; I think we can ignore it. * * If for some reason it would return 0, that means the previously waiting * task is already running, so it will observe condition true (or has already). */void swake_up_locked(struct swait_queue_head *q, int wake_flags){	struct swait_queue *curr; 	if (list_empty(&q->task_list))		return; 	curr = list_first_entry(&q->task_list, typeof(*curr), task_list);	try_to_wake_up(curr->task, TASK_NORMAL, wake_flags);	list_del_init(&curr->task_list);}EXPORT_SYMBOL(swake_up_locked); /* * Wake up all waiters. This is an interface which is solely exposed for * completions and not for general usage. * * It is intentionally different from swake_up_all() to allow usage from * hard interrupt context and interrupt disabled regions. */void swake_up_all_locked(struct swait_queue_head *q){	while (!list_empty(&q->task_list))		swake_up_locked(q, 0);} void swake_up_one(struct swait_queue_head *q){	unsigned long flags; 	raw_spin_lock_irqsave(&q->lock, flags);	swake_up_locked(q, 0);	raw_spin_unlock_irqrestore(&q->lock, flags);}EXPORT_SYMBOL(swake_up_one); /* * Does not allow usage from IRQ disabled, since we must be able to * release IRQs to guarantee bounded hold time. */void swake_up_all(struct swait_queue_head *q){	struct swait_queue *curr;	LIST_HEAD(tmp); 	raw_spin_lock_irq(&q->lock);	list_splice_init(&q->task_list, &tmp);	while (!list_empty(&tmp)) {		curr = list_first_entry(&tmp, typeof(*curr), task_list); 		wake_up_state(curr->task, TASK_NORMAL);		list_del_init(&curr->task_list); 		if (list_empty(&tmp))			break; 		raw_spin_unlock_irq(&q->lock);		raw_spin_lock_irq(&q->lock);	}	raw_spin_unlock_irq(&q->lock);}EXPORT_SYMBOL(swake_up_all); void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait){	wait->task = current;	if (list_empty(&wait->task_list))		list_add_tail(&wait->task_list, &q->task_list);} void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state){	unsigned long flags; 	raw_spin_lock_irqsave(&q->lock, flags);	__prepare_to_swait(q, wait);	set_current_state(state);	raw_spin_unlock_irqrestore(&q->lock, flags);}EXPORT_SYMBOL(prepare_to_swait_exclusive); long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state){	unsigned long flags;	long ret = 0; 	raw_spin_lock_irqsave(&q->lock, flags);	if (signal_pending_state(state, current)) {		/*		 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()		 * must not see us.		 */		list_del_init(&wait->task_list);		ret = -ERESTARTSYS;	} else {		__prepare_to_swait(q, wait);		set_current_state(state);	}	raw_spin_unlock_irqrestore(&q->lock, flags); 	return ret;}EXPORT_SYMBOL(prepare_to_swait_event); void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait){	__set_current_state(TASK_RUNNING);	if (!list_empty(&wait->task_list))		list_del_init(&wait->task_list);} void finish_swait(struct swait_queue_head *q, struct swait_queue *wait){	unsigned long flags; 	__set_current_state(TASK_RUNNING); 	if (!list_empty_careful(&wait->task_list)) {		raw_spin_lock_irqsave(&q->lock, flags);		list_del_init(&wait->task_list);		raw_spin_unlock_irqrestore(&q->lock, flags);	}}EXPORT_SYMBOL(finish_swait);