Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  * <linux/swait.h> (simple wait queues ) implementation:
       4             :  */
       5             : #include "sched.h"
       6             : 
       7         567 : void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
       8             :                              struct lock_class_key *key)
       9             : {
      10         567 :         raw_spin_lock_init(&q->lock);
      11         567 :         lockdep_set_class_and_name(&q->lock, key, name);
      12         567 :         INIT_LIST_HEAD(&q->task_list);
      13         567 : }
      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        2096 : void swake_up_locked(struct swait_queue_head *q)
      23             : {
      24        2096 :         struct swait_queue *curr;
      25             : 
      26        2096 :         if (list_empty(&q->task_list))
      27             :                 return;
      28             : 
      29        2008 :         curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
      30        2008 :         wake_up_process(curr->task);
      31        2008 :         list_del_init(&curr->task_list);
      32             : }
      33             : EXPORT_SYMBOL(swake_up_locked);
      34             : 
      35             : /*
      36             :  * Wake up all waiters. This is an interface which is solely exposed for
      37             :  * completions and not for general usage.
      38             :  *
      39             :  * It is intentionally different from swake_up_all() to allow usage from
      40             :  * hard interrupt context and interrupt disabled regions.
      41             :  */
      42          26 : void swake_up_all_locked(struct swait_queue_head *q)
      43             : {
      44          26 :         while (!list_empty(&q->task_list))
      45           0 :                 swake_up_locked(q);
      46          26 : }
      47             : 
      48        1679 : void swake_up_one(struct swait_queue_head *q)
      49             : {
      50        1679 :         unsigned long flags;
      51             : 
      52        1679 :         raw_spin_lock_irqsave(&q->lock, flags);
      53        1679 :         swake_up_locked(q);
      54        1679 :         raw_spin_unlock_irqrestore(&q->lock, flags);
      55        1679 : }
      56             : EXPORT_SYMBOL(swake_up_one);
      57             : 
      58             : /*
      59             :  * Does not allow usage from IRQ disabled, since we must be able to
      60             :  * release IRQs to guarantee bounded hold time.
      61             :  */
      62           0 : void swake_up_all(struct swait_queue_head *q)
      63             : {
      64           0 :         struct swait_queue *curr;
      65           0 :         LIST_HEAD(tmp);
      66             : 
      67           0 :         raw_spin_lock_irq(&q->lock);
      68           0 :         list_splice_init(&q->task_list, &tmp);
      69           0 :         while (!list_empty(&tmp)) {
      70           0 :                 curr = list_first_entry(&tmp, typeof(*curr), task_list);
      71             : 
      72           0 :                 wake_up_state(curr->task, TASK_NORMAL);
      73           0 :                 list_del_init(&curr->task_list);
      74             : 
      75           0 :                 if (list_empty(&tmp))
      76             :                         break;
      77             : 
      78           0 :                 raw_spin_unlock_irq(&q->lock);
      79           0 :                 raw_spin_lock_irq(&q->lock);
      80             :         }
      81           0 :         raw_spin_unlock_irq(&q->lock);
      82           0 : }
      83             : EXPORT_SYMBOL(swake_up_all);
      84             : 
      85        8172 : void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
      86             : {
      87         334 :         wait->task = current;
      88        8172 :         if (list_empty(&wait->task_list))
      89        5928 :                 list_add_tail(&wait->task_list, &q->task_list);
      90         334 : }
      91             : 
      92           0 : void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
      93             : {
      94           0 :         unsigned long flags;
      95             : 
      96           0 :         raw_spin_lock_irqsave(&q->lock, flags);
      97           0 :         __prepare_to_swait(q, wait);
      98           0 :         set_current_state(state);
      99           0 :         raw_spin_unlock_irqrestore(&q->lock, flags);
     100           0 : }
     101             : EXPORT_SYMBOL(prepare_to_swait_exclusive);
     102             : 
     103        7838 : long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
     104             : {
     105        7838 :         unsigned long flags;
     106        7838 :         long ret = 0;
     107             : 
     108        7838 :         raw_spin_lock_irqsave(&q->lock, flags);
     109        7838 :         if (signal_pending_state(state, current)) {
     110             :                 /*
     111             :                  * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
     112             :                  * must not see us.
     113             :                  */
     114           0 :                 list_del_init(&wait->task_list);
     115           0 :                 ret = -ERESTARTSYS;
     116             :         } else {
     117        7838 :                 __prepare_to_swait(q, wait);
     118        7838 :                 set_current_state(state);
     119             :         }
     120        7838 :         raw_spin_unlock_irqrestore(&q->lock, flags);
     121             : 
     122        7838 :         return ret;
     123             : }
     124             : EXPORT_SYMBOL(prepare_to_swait_event);
     125             : 
     126         334 : void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
     127             : {
     128         334 :         __set_current_state(TASK_RUNNING);
     129         334 :         if (!list_empty(&wait->task_list))
     130           0 :                 list_del_init(&wait->task_list);
     131         334 : }
     132             : 
     133        3921 : void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
     134             : {
     135        3921 :         unsigned long flags;
     136             : 
     137        3921 :         __set_current_state(TASK_RUNNING);
     138             : 
     139        3921 :         if (!list_empty_careful(&wait->task_list)) {
     140        3921 :                 raw_spin_lock_irqsave(&q->lock, flags);
     141        3921 :                 list_del_init(&wait->task_list);
     142        3921 :                 raw_spin_unlock_irqrestore(&q->lock, flags);
     143             :         }
     144        3921 : }
     145             : EXPORT_SYMBOL(finish_swait);