LXR linux/kernel/sched/swait.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * <linux/swait.h> (simple wait queues ) implementation:
   4 */
   5#include "sched.h"
   6
   7void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
   8                             struct lock_class_key *key)
   9{
  10        raw_spin_lock_init(&q->lock);
  11        lockdep_set_class_and_name(&q->lock, key, name);
  12        INIT_LIST_HEAD(&q->task_list);
  13}
  14EXPORT_SYMBOL(__init_swait_queue_head);
  15
  16/*
  17 * The thing about the wake_up_state() return value; I think we can ignore it.
  18 *
  19 * If for some reason it would return 0, that means the previously waiting
  20 * task is already running, so it will observe condition true (or has already).
  21 */
  22void swake_up_locked(struct swait_queue_head *q)
  23{
  24        struct swait_queue *curr;
  25
  26        if (list_empty(&q->task_list))
  27                return;
  28
  29        curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
  30        wake_up_process(curr->task);
  31        list_del_init(&curr->task_list);
  32}
  33EXPORT_SYMBOL(swake_up_locked);
  34
  35void swake_up_one(struct swait_queue_head *q)
  36{
  37        unsigned long flags;
  38
  39        raw_spin_lock_irqsave(&q->lock, flags);
  40        swake_up_locked(q);
  41        raw_spin_unlock_irqrestore(&q->lock, flags);
  42}
  43EXPORT_SYMBOL(swake_up_one);
  44
  45/*
  46 * Does not allow usage from IRQ disabled, since we must be able to
  47 * release IRQs to guarantee bounded hold time.
  48 */
  49void swake_up_all(struct swait_queue_head *q)
  50{
  51        struct swait_queue *curr;
  52        LIST_HEAD(tmp);
  53
  54        raw_spin_lock_irq(&q->lock);
  55        list_splice_init(&q->task_list, &tmp);
  56        while (!list_empty(&tmp)) {
  57                curr = list_first_entry(&tmp, typeof(*curr), task_list);
  58
  59                wake_up_state(curr->task, TASK_NORMAL);
  60                list_del_init(&curr->task_list);
  61
  62                if (list_empty(&tmp))
  63                        break;
  64
  65                raw_spin_unlock_irq(&q->lock);
  66                raw_spin_lock_irq(&q->lock);
  67        }
  68        raw_spin_unlock_irq(&q->lock);
  69}
  70EXPORT_SYMBOL(swake_up_all);
  71
  72static void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
  73{
  74        wait->task = current;
  75        if (list_empty(&wait->task_list))
  76                list_add_tail(&wait->task_list, &q->task_list);
  77}
  78
  79void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
  80{
  81        unsigned long flags;
  82
  83        raw_spin_lock_irqsave(&q->lock, flags);
  84        __prepare_to_swait(q, wait);
  85        set_current_state(state);
  86        raw_spin_unlock_irqrestore(&q->lock, flags);
  87}
  88EXPORT_SYMBOL(prepare_to_swait_exclusive);
  89
  90long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
  91{
  92        unsigned long flags;
  93        long ret = 0;
  94
  95        raw_spin_lock_irqsave(&q->lock, flags);
  96        if (signal_pending_state(state, current)) {
  97                /*
  98                 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
  99                 * must not see us.
 100                 */
 101                list_del_init(&wait->task_list);
 102                ret = -ERESTARTSYS;
 103        } else {
 104                __prepare_to_swait(q, wait);
 105                set_current_state(state);
 106        }
 107        raw_spin_unlock_irqrestore(&q->lock, flags);
 108
 109        return ret;
 110}
 111EXPORT_SYMBOL(prepare_to_swait_event);
 112
 113void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 114{
 115        __set_current_state(TASK_RUNNING);
 116        if (!list_empty(&wait->task_list))
 117                list_del_init(&wait->task_list);
 118}
 119
 120void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 121{
 122        unsigned long flags;
 123
 124        __set_current_state(TASK_RUNNING);
 125
 126        if (!list_empty_careful(&wait->task_list)) {
 127                raw_spin_lock_irqsave(&q->lock, flags);
 128                list_del_init(&wait->task_list);
 129                raw_spin_unlock_irqrestore(&q->lock, flags);
 130        }
 131}
 132EXPORT_SYMBOL(finish_swait);
 133