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