Zephyr events_zephyr 事件(1)

数据结构

k_event

struct k\_event {
	_wait_q_t         wait_q;
	uint32\_t          events;
	struct k\_spinlock lock;

	SYS\_PORT\_TRACING\_TRACKING\_FIELD(k_event)
};

• 该结构体中包含2个主要成员：
  • wait_q 等待队列，当线程调用等待函数时，如果条件不满足，那么将会被添加到等待队列中。
  • events 事件的状态，已发生为1，未发生为0。
• spinlock 是为了多线程安全操作。

event_walk_data

struct event\_walk\_data {
	struct k\_thread  \*head;
	uint32\_t events;
};

• 其中 events 为事件发布后事件对象中 events 成员变量的值，代表当前已经发生的事件。
• 当线程或者中断向事件对象发布事件时，因为等待事件被挂起的线程可能需要被唤醒，但是这些线程等待的事件并不相同，需要从等待队列 wait_q 中查找出满足唤醒条件的线程，并将这些线程作为节点添加到被唤醒链表中，head即为链表头。

static int event\_walk\_op(struct k\_thread \*thread, void \*data)
{
	unsigned int      wait_condition;
	struct event\_walk\_data \*event_data = data;

	wait_condition = thread->event_options & K_EVENT_WAIT_MASK;

	if (are\_wait\_conditions\_met(thread->events, event_data->events,
				    wait_condition)) {

		/\*
 \* Events create a list of threads to wake up. We do
 \* not want z\_thread\_timeout to wake these threads; they
 \* will be woken up by k\_event\_post\_internal once they
 \* have been processed.
 \*/
		thread->no_wake_on_timeout = true;

		/\*
 \* The wait conditions have been satisfied. Add this
 \* thread to the list of threads to unpend.
 \*/
		thread->next_event_link = event_data->head;
		event_data->head = thread;
		z\_abort\_timeout(&thread->base.timeout);