fix(sched): guard wait queue state transitions

docs/agents/tasks/04-time-scheduler.md

@@ -147,6 +147,7 @@
 - 已提供 `sched_sleep()`，线程可以睡眠指定 tick 数并被 timer 唤醒。
 - 已提供 `wait_queue_init()`、`wait_queue_sleep()`、`wait_queue_wake_one()` 和 `wait_queue_wake_all()`。
 - 已提供 `wait_queue_wait()` 和 `wait_queue_wait_timeout()`，调用方可以等待条件成立，并在超时路径上获得失败返回值。
+- wait queue 已有内部 interrupt-safe lock，条件检查、等待入队和 wakeup 队列修改已收敛到同一同步边界，降低 lost wakeup 风险。
 - 已建立单 CPU interrupt-safe lock 基础，当前 `spin_lock_irqsave()` 会保存并关闭中断，`spin_unlock_irqrestore()` 会恢复原中断状态。
 - 已把 `kernel_thread_create()` 中的线程 id 分配和 run queue 入队纳入 interrupt-safe lock 保护。
 - 已建立 `sched_irq_exit()`，timer IRQ 只设置 `need_resched`，trap 的 IRQ 返回边界统一消费调度请求。
@@ -165,7 +166,7 @@
 ### B. wait queue 锁语义
 
 - 为 wait queue 增加内部锁或要求调用方持有指定锁，并在接口命名中体现约束。
-- 把条件检查、等待入队和睡眠切换收敛成一个不会丢唤醒的模式。
+- 继续把条件所属数据的修改规则文档化；当前 wait queue 内部锁已经覆盖条件检查、等待入队和 wakeup 队列修改。
 - 区分 `wake_one`、`wake_all`、timeout wakeup 和条件 wakeup 的状态处理。
 - 检查 wakeup 是否可能唤醒 DEAD、RUNNING 或未入队线程。
 

include/tianole/sched.h

@@ -4,6 +4,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <tianole/spinlock.h>
+
 typedef void (*kernel_thread_entry_t)(void *arg);
 typedef int (*wait_condition_t)(void *arg);
 
@@ -16,6 +18,7 @@ enum thread_state {
 };
 
 struct wait_queue {
+	struct spinlock lock;
 	struct thread *head;
 	struct thread *tail;
 };

kernel/sched/wait.c

@@ -9,11 +9,13 @@ void wait_queue_init(struct wait_queue *queue)
 		return;
 	}
 
+	queue->lock.locked = 0;
 	queue->head = 0;
 	queue->tail = 0;
 }
 
-static void wait_queue_enqueue(struct wait_queue *queue, struct thread *thread)
+static void wait_queue_enqueue_locked(
+	struct wait_queue *queue, struct thread *thread)
 {
 	thread->wait_next = 0;
 
@@ -26,7 +28,8 @@ static void wait_queue_enqueue(struct wait_queue *queue, struct thread *thread)
 	queue->tail = thread;
 }
 
-static void wait_queue_remove(struct wait_queue *queue, struct thread *target)
+static void wait_queue_remove_locked(
+	struct wait_queue *queue, struct thread *target)
 {
 	struct thread *prev = 0;
 	struct thread *thread;
@@ -55,29 +58,66 @@ static void wait_queue_remove(struct wait_queue *queue, struct thread *target)
 	}
 }
 
+static void wait_queue_mark_ready_locked(struct thread *thread)
+{
+	if (thread->state == THREAD_WAITING ||
+		thread->state == THREAD_SLEEPING) {
+		thread->wake_tick = 0;
+		thread->state = THREAD_READY;
+	}
+}
+
 void wait_queue_sleep(struct wait_queue *queue)
 {
+	uint64_t flags;
+
 	if (queue == 0 || current_thread == 0) {
 		return;
 	}
 
-	wait_queue_enqueue(queue, current_thread);
+	spin_lock_irqsave(&queue->lock, &flags);
+	wait_queue_enqueue_locked(queue, current_thread);
 	current_thread->state = THREAD_WAITING;
-	sched_yield();
+	spin_unlock_irqrestore(&queue->lock, flags);
+
+	for (;;) {
+		sched_yield();
+
+		spin_lock_irqsave(&queue->lock, &flags);
+		if (current_thread->state != THREAD_WAITING) {
+			spin_unlock_irqrestore(&queue->lock, flags);
+			return;
+		}
+		spin_unlock_irqrestore(&queue->lock, flags);
+	}
 }
 
 int wait_queue_wait(
 	struct wait_queue *queue, wait_condition_t condition, void *arg)
 {
+	uint64_t flags;
+
 	if (queue == 0 || condition == 0 || current_thread == 0) {
 		return -1;
 	}
 
-	while (condition(arg) == 0) {
-		wait_queue_sleep(queue);
-	}
+	for (;;) {
+		spin_lock_irqsave(&queue->lock, &flags);
+		if (condition(arg) != 0) {
+			spin_unlock_irqrestore(&queue->lock, flags);
+			return 0;
+		}
 
-	return 0;
+		wait_queue_enqueue_locked(queue, current_thread);
+		current_thread->state = THREAD_WAITING;
+		spin_unlock_irqrestore(&queue->lock, flags);
+
+		sched_yield();
+
+		spin_lock_irqsave(&queue->lock, &flags);
+		wait_queue_remove_locked(queue, current_thread);
+		spin_unlock_irqrestore(&queue->lock, flags);
+	}
 }
 
 int wait_queue_wait_timeout(struct wait_queue *queue,
@@ -86,6 +126,7 @@ int wait_queue_wait_timeout(struct wait_queue *queue,
 	uint64_t ticks)
 {
 	uint64_t deadline;
+	uint64_t flags;
 
 	if (queue == 0 || condition == 0 || current_thread == 0) {
 		return -1;
@@ -100,29 +141,47 @@ int wait_queue_wait_timeout(struct wait_queue *queue,
 	}
 
 	deadline = timer_ticks() + ticks;
-	while (condition(arg) == 0) {
+	for (;;) {
 		uint64_t now = timer_ticks();
 
+		spin_lock_irqsave(&queue->lock, &flags);
+		if (condition(arg) != 0) {
+			current_thread->wake_tick = 0;
+			spin_unlock_irqrestore(&queue->lock, flags);
+			return 0;
+		}
+
 		if (now >= deadline) {
+			current_thread->wake_tick = 0;
+			spin_unlock_irqrestore(&queue->lock, flags);
 			return -1;
 		}
 
 		current_thread->wake_tick = deadline;
 		current_thread->state = THREAD_SLEEPING;
-		wait_queue_enqueue(queue, current_thread);
-		sched_yield();
-		wait_queue_remove(queue, current_thread);
-	}
+		wait_queue_enqueue_locked(queue, current_thread);
+		spin_unlock_irqrestore(&queue->lock, flags);
 
-	current_thread->wake_tick = 0;
-	return 0;
+		sched_yield();
+
+		spin_lock_irqsave(&queue->lock, &flags);
+		wait_queue_remove_locked(queue, current_thread);
+		spin_unlock_irqrestore(&queue->lock, flags);
+	}
 }
 
 void wait_queue_wake_one(struct wait_queue *queue)
 {
 	struct thread *thread;
+	uint64_t flags;
 
-	if (queue == 0 || queue->head == 0) {
+	if (queue == 0) {
+		return;
+	}
+
+	spin_lock_irqsave(&queue->lock, &flags);
+	if (queue->head == 0) {
+		spin_unlock_irqrestore(&queue->lock, flags);
 		return;
 	}
 
@@ -133,16 +192,29 @@ void wait_queue_wake_one(struct wait_queue *queue)
 	}
 
 	thread->wait_next = 0;
-	if (thread->state == THREAD_WAITING ||
-		thread->state == THREAD_SLEEPING) {
-		thread->wake_tick = 0;
-		thread->state = THREAD_READY;
-	}
+	wait_queue_mark_ready_locked(thread);
+	spin_unlock_irqrestore(&queue->lock, flags);
 }
 
 void wait_queue_wake_all(struct wait_queue *queue)
 {
-	while (queue != 0 && queue->head != 0) {
-		wait_queue_wake_one(queue);
+	struct thread *thread;
+	uint64_t flags;
+
+	if (queue == 0) {
+		return;
 	}
+
+	spin_lock_irqsave(&queue->lock, &flags);
+	while (queue->head != 0) {
+		thread = queue->head;
+		queue->head = thread->wait_next;
+		if (queue->head == 0) {
+			queue->tail = 0;
+		}
+
+		thread->wait_next = 0;
+		wait_queue_mark_ready_locked(thread);
+	}
+	spin_unlock_irqrestore(&queue->lock, flags);
 }