kernel/sched/swait.c

Source file repositories/reference/linux-study-clean/kernel/sched/swait.c

File Facts

System
Linux kernel
Corpus path
kernel/sched/swait.c
Extension
.c
Size
3746 bytes
Lines
146
Domain
Core OS
Bucket
Scheduler, Processes, Timers, Sync, And Syscalls
Inferred role
Core OS: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 * <linux/swait.h> (simple wait queues ) implementation:
 */
#include "sched.h"

void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
			     struct lock_class_key *key)
{
	raw_spin_lock_init(&q->lock);
	lockdep_set_class_and_name(&q->lock, key, name);
	INIT_LIST_HEAD(&q->task_list);
}
EXPORT_SYMBOL(__init_swait_queue_head);

/*
 * The thing about the wake_up_state() return value; I think we can ignore it.
 *
 * If for some reason it would return 0, that means the previously waiting
 * task is already running, so it will observe condition true (or has already).
 */
void swake_up_locked(struct swait_queue_head *q, int wake_flags)
{
	struct swait_queue *curr;

	if (list_empty(&q->task_list))
		return;

	curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
	try_to_wake_up(curr->task, TASK_NORMAL, wake_flags);
	list_del_init(&curr->task_list);
}
EXPORT_SYMBOL(swake_up_locked);

/*
 * Wake up all waiters. This is an interface which is solely exposed for
 * completions and not for general usage.
 *
 * It is intentionally different from swake_up_all() to allow usage from
 * hard interrupt context and interrupt disabled regions.
 */
void swake_up_all_locked(struct swait_queue_head *q)
{
	while (!list_empty(&q->task_list))
		swake_up_locked(q, 0);
}

void swake_up_one(struct swait_queue_head *q)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&q->lock, flags);
	swake_up_locked(q, 0);
	raw_spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(swake_up_one);

/*
 * Does not allow usage from IRQ disabled, since we must be able to
 * release IRQs to guarantee bounded hold time.
 */
void swake_up_all(struct swait_queue_head *q)
{
	struct swait_queue *curr;
	LIST_HEAD(tmp);

	raw_spin_lock_irq(&q->lock);
	list_splice_init(&q->task_list, &tmp);
	while (!list_empty(&tmp)) {
		curr = list_first_entry(&tmp, typeof(*curr), task_list);

		wake_up_state(curr->task, TASK_NORMAL);
		list_del_init(&curr->task_list);

		if (list_empty(&tmp))
			break;

		raw_spin_unlock_irq(&q->lock);
		raw_spin_lock_irq(&q->lock);
	}
	raw_spin_unlock_irq(&q->lock);
}
EXPORT_SYMBOL(swake_up_all);

void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
{
	wait->task = current;
	if (list_empty(&wait->task_list))
		list_add_tail(&wait->task_list, &q->task_list);
}

Annotation

Implementation Notes