kernel/sched/swait.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * <linux/swait.h> (simple wait queues ) implementation:
   4  */
   5
   6 void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
   7                              struct lock_class_key *key)
   8 {
   9         raw_spin_lock_init(&q->lock);
  10         lockdep_set_class_and_name(&q->lock, key, name);
  11         INIT_LIST_HEAD(&q->task_list);
  12 }
  13 EXPORT_SYMBOL(__init_swait_queue_head);
  14
  15 /*
  16  * The thing about the wake_up_state() return value; I think we can ignore it.
  17  *
  18  * If for some reason it would return 0, that means the previously waiting
  19  * task is already running, so it will observe condition true (or has already).
  20  */
  21 void swake_up_locked(struct swait_queue_head *q)
  22 {
  23         struct swait_queue *curr;
  24
  25         if (list_empty(&q->task_list))
  26                 return;
  27
  28         curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
  29         wake_up_process(curr->task);
  30         list_del_init(&curr->task_list);
  31 }
  32 EXPORT_SYMBOL(swake_up_locked);
  33
  34 /*
  35  * Wake up all waiters. This is an interface which is solely exposed for
  36  * completions and not for general usage.
  37  *
  38  * It is intentionally different from swake_up_all() to allow usage from
  39  * hard interrupt context and interrupt disabled regions.
  40  */
  41 void swake_up_all_locked(struct swait_queue_head *q)
  42 {
  43         while (!list_empty(&q->task_list))
  44                 swake_up_locked(q);
  45 }
  46
  47 void swake_up_one(struct swait_queue_head *q)
  48 {
  49         unsigned long flags;
  50
  51         raw_spin_lock_irqsave(&q->lock, flags);
  52         swake_up_locked(q);
  53         raw_spin_unlock_irqrestore(&q->lock, flags);
  54 }
  55 EXPORT_SYMBOL(swake_up_one);
  56
  57 /*
  58  * Does not allow usage from IRQ disabled, since we must be able to
  59  * release IRQs to guarantee bounded hold time.
  60  */
  61 void swake_up_all(struct swait_queue_head *q)
  62 {
  63         struct swait_queue *curr;
  64         LIST_HEAD(tmp);
  65
  66         raw_spin_lock_irq(&q->lock);
  67         list_splice_init(&q->task_list, &tmp);
  68         while (!list_empty(&tmp)) {
  69                 curr = list_first_entry(&tmp, typeof(*curr), task_list);
  70
  71                 wake_up_state(curr->task, TASK_NORMAL);
  72                 list_del_init(&curr->task_list);
  73
  74                 if (list_empty(&tmp))
  75                         break;
  76
  77                 raw_spin_unlock_irq(&q->lock);
  78                 raw_spin_lock_irq(&q->lock);
  79         }
  80         raw_spin_unlock_irq(&q->lock);
  81 }
  82 EXPORT_SYMBOL(swake_up_all);
  83
  84 void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
  85 {
  86         wait->task = current;
  87         if (list_empty(&wait->task_list))
  88                 list_add_tail(&wait->task_list, &q->task_list);
  89 }
  90
  91 void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
  92 {
  93         unsigned long flags;
  94
  95         raw_spin_lock_irqsave(&q->lock, flags);
  96         __prepare_to_swait(q, wait);
  97         set_current_state(state);
  98         raw_spin_unlock_irqrestore(&q->lock, flags);
  99 }
 100 EXPORT_SYMBOL(prepare_to_swait_exclusive);
 101
 102 long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
 103 {
 104         unsigned long flags;
 105         long ret = 0;
 106
 107         raw_spin_lock_irqsave(&q->lock, flags);
 108         if (signal_pending_state(state, current)) {
 109                 /*
 110                  * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
 111                  * must not see us.
 112                  */
 113                 list_del_init(&wait->task_list);
 114                 ret = -ERESTARTSYS;
 115         } else {
 116                 __prepare_to_swait(q, wait);
 117                 set_current_state(state);
 118         }
 119         raw_spin_unlock_irqrestore(&q->lock, flags);
 120
 121         return ret;
 122 }
 123 EXPORT_SYMBOL(prepare_to_swait_event);
 124
 125 void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 126 {
 127         __set_current_state(TASK_RUNNING);
 128         if (!list_empty(&wait->task_list))
 129                 list_del_init(&wait->task_list);
 130 }
 131
 132 void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 133 {
 134         unsigned long flags;
 135
 136         __set_current_state(TASK_RUNNING);
 137
 138         if (!list_empty_careful(&wait->task_list)) {
 139                 raw_spin_lock_irqsave(&q->lock, flags);
 140                 list_del_init(&wait->task_list);
 141                 raw_spin_unlock_irqrestore(&q->lock, flags);
 142         }
 143 }
 144 EXPORT_SYMBOL(finish_swait);