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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Copyright (C) 2026 Richard Qin */
/*
* WaitQueue — blocking synchronization implementation
*
* sleep(): current task → Sleeping, link into queue, schedule()
* wake_one(): dequeue head task → Runnable, sched_enqueue()
*
* The internal spinlock protects the wait list only.
* schedule() is called AFTER releasing the spinlock to avoid
* holding a lock across a context switch.
*/
#include <lume/waitqueue.h>
#include <lume/task.h>
#include <lume/sched.h>
#include <lume/kprintf.h>
#include <arch/cpu.h>
void WaitQueue::sleep(Spinlock* external_lock)
{
TaskControlBlock* curr = current_task();
if (!curr) {
if (external_lock) external_lock->release();
return;
}
{
LockGuard guard(lock_);
/* Mark task as sleeping */
curr->state = TaskState::Sleeping;
/* Remove from RunQueue (sched_dequeue acquires its own lock) */
/* We do NOT call sched_dequeue here because schedule() handles
* the put_prev_task logic when state != Running. */
/* Link into wait queue tail */
list_node* node = &curr->run_link;
node->prev = head_.prev;
node->next = &head_;
head_.prev->next = node;
head_.prev = node;
}
if (external_lock) {
external_lock->release();
}
/* Context switch away — will return here when woken */
schedule();
}
bool WaitQueue::wake_one()
{
LockGuard guard(lock_);
if (head_.is_empty())
return false;
/* Dequeue the first (oldest) waiter */
list_node* node = head_.next;
node->prev->next = node->next;
node->next->prev = node->prev;
node->init();
TaskControlBlock* task =
list_entry<TaskControlBlock, &TaskControlBlock::run_link>(node);
task->state = TaskState::Runnable;
sched_enqueue(task);
return true;
}
int WaitQueue::wake_all()
{
LockGuard guard(lock_);
int count = 0;
while (!head_.is_empty()) {
list_node* node = head_.next;
node->prev->next = node->next;
node->next->prev = node->prev;
node->init();
TaskControlBlock* task =
list_entry<TaskControlBlock, &TaskControlBlock::run_link>(node);
task->state = TaskState::Runnable;
sched_enqueue(task);
count++;
}
return count;
}
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