kernel/sched/swait.c

   1 #include <linux/sched.h>
   2 #include <linux/swait.h>
   3
   4 void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
   5                              struct lock_class_key *key)
   6 {
   7         raw_spin_lock_init(&q->lock);
   8         lockdep_set_class_and_name(&q->lock, key, name);
   9         INIT_LIST_HEAD(&q->task_list);
  10 }
  11 EXPORT_SYMBOL(__init_swait_queue_head);
  12
  13 /*
  14  * The thing about the wake_up_state() return value; I think we can ignore it.
  15  *
  16  * If for some reason it would return 0, that means the previously waiting
  17  * task is already running, so it will observe condition true (or has already).
  18  */
  19 void swake_up_locked(struct swait_queue_head *q)
  20 {
  21         struct swait_queue *curr;
  22
  23         if (list_empty(&q->task_list))
  24                 return;
  25
  26         curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
  27         wake_up_process(curr->task);
  28         list_del_init(&curr->task_list);
  29 }
  30 EXPORT_SYMBOL(swake_up_locked);
  31
  32 void swake_up(struct swait_queue_head *q)
  33 {
  34         unsigned long flags;
  35
  36         if (!swait_active(q))
  37                 return;
  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);
  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         if (!swait_active(q))
  55                 return;
  56
  57         raw_spin_lock_irq(&q->lock);
  58         list_splice_init(&q->task_list, &tmp);
  59         while (!list_empty(&tmp)) {
  60                 curr = list_first_entry(&tmp, typeof(*curr), task_list);
  61
  62                 wake_up_state(curr->task, TASK_NORMAL);
  63                 list_del_init(&curr->task_list);
  64
  65                 if (list_empty(&tmp))
  66                         break;
  67
  68                 raw_spin_unlock_irq(&q->lock);
  69                 raw_spin_lock_irq(&q->lock);
  70         }
  71         raw_spin_unlock_irq(&q->lock);
  72 }
  73 EXPORT_SYMBOL(swake_up_all);
  74
  75 void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
  76 {
  77         wait->task = current;
  78         if (list_empty(&wait->task_list))
  79                 list_add(&wait->task_list, &q->task_list);
  80 }
  81
  82 void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
  83 {
  84         unsigned long flags;
  85
  86         raw_spin_lock_irqsave(&q->lock, flags);
  87         __prepare_to_swait(q, wait);
  88         set_current_state(state);
  89         raw_spin_unlock_irqrestore(&q->lock, flags);
  90 }
  91 EXPORT_SYMBOL(prepare_to_swait);
  92
  93 long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
  94 {
  95         if (signal_pending_state(state, current))
  96                 return -ERESTARTSYS;
  97
  98         prepare_to_swait(q, wait, state);
  99
 100         return 0;
 101 }
 102 EXPORT_SYMBOL(prepare_to_swait_event);
 103
 104 void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 105 {
 106         __set_current_state(TASK_RUNNING);
 107         if (!list_empty(&wait->task_list))
 108                 list_del_init(&wait->task_list);
 109 }
 110
 111 void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 112 {
 113         unsigned long flags;
 114
 115         __set_current_state(TASK_RUNNING);
 116
 117         if (!list_empty_careful(&wait->task_list)) {
 118                 raw_spin_lock_irqsave(&q->lock, flags);
 119                 list_del_init(&wait->task_list);
 120                 raw_spin_unlock_irqrestore(&q->lock, flags);
 121         }
 122 }
 123 EXPORT_SYMBOL(finish_swait);