事件集先进先出方式如何理解？

发布于 2021-08-18 21:42:00 浏览：1280 订阅该版

修改了下参考文档中的事件集例程，采用RT_IPC_FLAG_FIFO方式，线程1和3等待相同事件集（事件接受设置为不清除），事件集唤醒线程后则打印线程退出；线程2发送事件集。结果显示线程1、3唤醒的顺序与线程挂起的顺序无关，与线程1、3优先级有关，高优先级先执行，低优先级后执行。
注：
1）RTT:V4.0.3, IDE:VSCode , BSP:qemu-express-a9
线程1初始化后延时100ms等待事件集；线程3初始化后直接等待事件集；即等待顺序为线程3在前，线程1在后，Finsh执行list_event看到的等待线程顺序与此一致；
2）测试代码优先级线程1高于线程3，等待顺序为线程3、线程1，线程接收事件集顺序为线程1、线程3，即与先进先出不符，与优先级相符；
3）交换线程1、线程3优先级，则线程接收事件集顺序为线程3、线程1，还是与优先级相符。
请问是不是对FIFO方式理解有误，线程等待顺序与等待线程列表里的顺序不是一回事？理解是否可推广道其它同步方式？
测试代码：
```c
#include <rtthread.h>
#include "thread_exp.h"

#define THREAD_PRIORITY      9
#define THREAD_TIMESLICE     5

#define EVENT_FLAG1 (1 << 0)
#define EVENT_FLAG2 (1 << 1)
#define EVENT_FLAG3 (1 << 2)
#define EVENT_FLAG4 (1 << 3)
#define EVENT_FLAG5 (1 << 4)
#define EVENT_FLAG6 (1 << 5)

/* 事件控制块 */
static struct rt_event event;

ALIGN(RT_ALIGN_SIZE)
static char thread1_stack[1024];
static struct rt_thread thread1;

/* 线程 1 入口函数 */
static void thread1_recv_event(void *param)
{
    rt_uint32_t e;
    /*
    rt_kprintf("thread1 waitting for 1 and 2.\n");
    if (rt_event_recv(&event, (EVENT_FLAG1 | EVENT_FLAG2),
                      RT_EVENT_FLAG_AND | RT_EVENT_FLAG_CLEAR,
                      RT_WAITING_FOREVER, &e) == RT_EOK)
    {
        rt_kprintf("thread1: OR recv event 0x%x\n", e);
    }
    */

//rt_kprintf("thread1: delay 1s to prepare the second event\n");
    rt_thread_mdelay(100);

rt_kprintf("thread1 waitting for 4 and 5.\n");
    if (rt_event_recv(&event, (EVENT_FLAG4 | EVENT_FLAG5),
                      RT_EVENT_FLAG_AND,
                      RT_WAITING_FOREVER, &e) == RT_EOK)
    {
        rt_kprintf("thread1: AND recv event 0x%x\n", e);
    }
    rt_kprintf("thread1 leave.\n");
}

ALIGN(RT_ALIGN_SIZE)
static char thread3_stack[1024];
static struct rt_thread thread3;

/* 线程 1 入口函数 */
static void thread3_recv_event(void *param)
{
    rt_uint32_t e;
    rt_kprintf("thread3 waitting for 4 and 5.\n");
    /* 第二次接收事件，事件 3 和事件 5 均发生时才可以触发线程 1，接收完后清除事件标志 */
    if (rt_event_recv(&event, (EVENT_FLAG4 | EVENT_FLAG5),
                      RT_EVENT_FLAG_AND,
                      RT_WAITING_FOREVER, &e) == RT_EOK)
    {
        rt_kprintf("thread3: AND recv event 0x%x\n", e);
    }
    rt_kprintf("thread3 leave.\n");
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;

/* 线程 2 入口 */
static void thread2_send_event(void *param)
{
    rt_thread_mdelay(2000);
    rt_kprintf("thread2: send event1\n");
    rt_event_send(&event, EVENT_FLAG1);
    rt_thread_mdelay(200);

rt_kprintf("thread2: send event2\n");
    rt_event_send(&event, EVENT_FLAG2);
    rt_thread_mdelay(200);

rt_kprintf("thread2: send event3\n");
    rt_event_send(&event, EVENT_FLAG3);
    rt_thread_mdelay(200);

rt_kprintf("thread2: send event4\n");
    rt_event_send(&event, EVENT_FLAG4);
    rt_thread_mdelay(200);

rt_kprintf("thread2: send event5\n");
    rt_event_send(&event, EVENT_FLAG5);

rt_kprintf("thread2 leave.\n");
}

int event_sample(void)
{
    rt_err_t result;

//rt_scheduler_sethook(hook_of_scheduler);

/* 初始化事件对象 */
    result = rt_event_init(&event, "event", RT_IPC_FLAG_FIFO);
    if (result != RT_EOK)
    {
        rt_kprintf("init event failed.\n");
        return -1;
    }

rt_thread_init(&thread1,
                   "thread1",
                   thread1_recv_event,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack),
                   THREAD_PRIORITY - 2, THREAD_TIMESLICE);
    rt_thread_startup(&thread1);

rt_thread_init(&thread3,
                   "thread3",
                   thread3_recv_event,
                   RT_NULL,
                   &thread3_stack[0],
                   sizeof(thread3_stack),
                   THREAD_PRIORITY-1, THREAD_TIMESLICE);
    rt_thread_startup(&thread3);

rt_thread_init(&thread2,
                   "thread2",
                   thread2_send_event,
                   RT_NULL,
                   &thread2_stack[0],
                   sizeof(thread2_stack),
                   THREAD_PRIORITY, THREAD_TIMESLICE);
    rt_thread_startup(&thread2);

return 0;
}
```
结果如下：
```
 \ | /
- RT -     Thread Operating System
 / | \     4.0.3 build Aug 16 2021
 2006 - 2021 Copyright by rt-thread team
lwIP-2.0.2 initialized!
[32m[I/sal.skt] Socket Abstraction Layer initialize success.[0m
[32m[I/SDIO] SD card capacity 65536 KB.[0m
[32m[I/SDIO] switching card to high speed failed![0m
hello rt-thread
msh />ev
event_sample
msh />event_sample
thread3 waitting for 4 and 5.
msh />thread1 waitting for 4 and 5.
thread2: send event1
thread2: send event2
thread2: send event3
thread2: send event4
thread2: send event5
thread1: AND recv event 0x18
thread1 leave.
thread3: AND recv event 0x18
thread3 leave.
thread2 leave.
```