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, int wake_flags) 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 try_to_wake_up(curr->task, TASK_NORMAL, wake_flags); 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, 0); 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, 0); 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); 145