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
   7 void __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 }
  14 EXPORT_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  */
  22 void 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 }
  33 EXPORT_SYMBOL(swake_up_locked);
  34
  35 void 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 }
  43 EXPORT_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  */
  49 void 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 }
  70 EXPORT_SYMBOL(swake_up_all);
  71
  72 static 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
  79 void 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 }
  88 EXPORT_SYMBOL(prepare_to_swait_exclusive);
  89
  90 long 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 }
 111 EXPORT_SYMBOL(prepare_to_swait_event);
 112
 113 void __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
 120 void 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 }
 132 EXPORT_SYMBOL(finish_swait);