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         raw_spin_lock_irqsave(&q->lock, flags);
  37         swake_up_locked(q);
  38         raw_spin_unlock_irqrestore(&q->lock, flags);
  39 }
  40 EXPORT_SYMBOL(swake_up);
  41
  42 /*
  43  * Does not allow usage from IRQ disabled, since we must be able to
  44  * release IRQs to guarantee bounded hold time.
  45  */
  46 void swake_up_all(struct swait_queue_head *q)
  47 {
  48         struct swait_queue *curr;
  49         LIST_HEAD(tmp);
  50
  51         raw_spin_lock_irq(&q->lock);
  52         list_splice_init(&q->task_list, &tmp);
  53         while (!list_empty(&tmp)) {
  54                 curr = list_first_entry(&tmp, typeof(*curr), task_list);
  55
  56                 wake_up_state(curr->task, TASK_NORMAL);
  57                 list_del_init(&curr->task_list);
  58
  59                 if (list_empty(&tmp))
  60                         break;
  61
  62                 raw_spin_unlock_irq(&q->lock);
  63                 raw_spin_lock_irq(&q->lock);
  64         }
  65         raw_spin_unlock_irq(&q->lock);
  66 }
  67 EXPORT_SYMBOL(swake_up_all);
  68
  69 void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
  70 {
  71         wait->task = current;
  72         if (list_empty(&wait->task_list))
  73                 list_add(&wait->task_list, &q->task_list);
  74 }
  75
  76 void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
  77 {
  78         unsigned long flags;
  79
  80         raw_spin_lock_irqsave(&q->lock, flags);
  81         __prepare_to_swait(q, wait);
  82         set_current_state(state);
  83         raw_spin_unlock_irqrestore(&q->lock, flags);
  84 }
  85 EXPORT_SYMBOL(prepare_to_swait);
  86
  87 long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
  88 {
  89         if (signal_pending_state(state, current))
  90                 return -ERESTARTSYS;
  91
  92         prepare_to_swait(q, wait, state);
  93
  94         return 0;
  95 }
  96 EXPORT_SYMBOL(prepare_to_swait_event);
  97
  98 void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
  99 {
 100         __set_current_state(TASK_RUNNING);
 101         if (!list_empty(&wait->task_list))
 102                 list_del_init(&wait->task_list);
 103 }
 104
 105 void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 106 {
 107         unsigned long flags;
 108
 109         __set_current_state(TASK_RUNNING);
 110
 111         if (!list_empty_careful(&wait->task_list)) {
 112                 raw_spin_lock_irqsave(&q->lock, flags);
 113                 list_del_init(&wait->task_list);
 114                 raw_spin_unlock_irqrestore(&q->lock, flags);
 115         }
 116 }
 117 EXPORT_SYMBOL(finish_swait);