RT-thread線(xiàn)程切換原理與實(shí)現(xiàn)

RTThread官網(wǎng)看一下，可以發(fā)現(xiàn)【rt_thread_suspend】的函數(shù)說(shuō)明中，特意的說(shuō)明了這個(gè)函數(shù)不能通過(guò)A線(xiàn)程掛起B(yǎng)線(xiàn)程。

翻開(kāi)源碼看一下，在這個(gè)函數(shù)中有這么一個(gè)判斷，會(huì)判斷需要掛起線(xiàn)程的狀態(tài)，如果線(xiàn)程不等于就緒態(tài)那么就不會(huì)進(jìn)入掛起，而sleep，delay等函數(shù)都會(huì)導(dǎo)致線(xiàn)程的掛起，那么其他線(xiàn)程想要掛起這個(gè)線(xiàn)程肯定會(huì)掉到這個(gè)if里面，從而掛起不了這個(gè)線(xiàn)程。

這里有兩個(gè)解決思路，一個(gè)是通過(guò) rt_thread_detach(&thread)刪除線(xiàn)程的方法實(shí)現(xiàn)，另外一個(gè)就是定義一個(gè)暫停信號(hào)量，然后在需要暫停的線(xiàn)程中去不停的監(jiān)測(cè)這個(gè)信號(hào)量，當(dāng)接收到信號(hào)量時(shí)，自己主動(dòng)掛起線(xiàn)程并讓出CPU，這樣就可以實(shí)現(xiàn)暫停線(xiàn)程，而且還能夠知道線(xiàn)程暫停在哪，下面就第二個(gè)思路進(jìn)行的代碼實(shí)現(xiàn)如下：

#include 
ALIGN(RT_ALIGN_SIZE)
static rt_uint8_t a_thread_stack[ 512 ];
ALIGN(RT_ALIGN_SIZE)
static rt_uint8_t b_thread_stack[ 512 ];
ALIGN(RT_ALIGN_SIZE)
static rt_uint8_t c_thread_stack[ 512 ];
static struct rt_thread a_thread;
static struct rt_thread b_thread;
static struct rt_thread c_thread;
static rt_sem_t b_pause_sem = RT_NULL;
static rt_sem_t c_pause_sem = RT_NULL;
static void a_thread_entry(void *parameter)
{
   unsigned int count = 0;
   while (1)
   {
       count++;
       if(count == 10)
       {
           rt_kprintf("b start!\n");
           rt_thread_startup(&b_thread);   //開(kāi)始掃地
       }
       else if(count == 30)
       {
           rt_kprintf("b pause!\n");
           rt_sem_release(b_pause_sem);//rt_thread_suspend(&b_thread);   //停止掃地
           rt_kprintf("c start!\n");
           rt_thread_startup(&c_thread);   //開(kāi)始洗碗
       }
       else if(count == 50)
       {
           rt_kprintf("c pause!\n");
           rt_sem_release(c_pause_sem);//rt_thread_suspend(&c_thread);   //停止洗碗
           rt_kprintf("b start!\n");
           rt_thread_resume(&b_thread);    //開(kāi)始掃地
       }
       rt_thread_delay(100);
   }
}
static void b_thread_entry(void *parameter)
{
   unsigned int count = 0;
   while (1)
   {
       rt_kprintf("b thread run!\n");
       rt_thread_delay(300);
       if(rt_sem_take(b_pause_sem, 0) == RT_EOK)
       {
           rt_thread_suspend(&b_thread);   //停止掃地
           rt_schedule();
       }
   }
}
static void c_thread_entry(void *parameter)
{
   unsigned int count = 0;
   while (1)
   {
       rt_kprintf("c thread run!\n");
       rt_thread_delay(100);
       if(rt_sem_take(c_pause_sem, 0) == RT_EOK)
       {
           rt_thread_suspend(&c_thread);   //停止掃地
           rt_schedule();
       }
   }
}
int pause_thread_init(void)
{
   rt_err_t result;
  
   b_pause_sem = rt_sem_create("b_pause", 0, RT_IPC_FLAG_PRIO);
  
   c_pause_sem = rt_sem_create("c_pause", 0, RT_IPC_FLAG_PRIO);
   /* init led thread */
   result = rt_thread_init(&a_thread,
                           "a_thread",
                           a_thread_entry,
                           RT_NULL,
                           (rt_uint8_t *)&a_thread_stack[0],
                           sizeof(a_thread_stack),
                           5,
                           5);
                          
   if (result == RT_EOK)
   {
       rt_thread_startup(&a_thread);
   }
  
   /* init led thread */
   result = rt_thread_init(&b_thread,
                           "b_thread",
                           b_thread_entry,
                           RT_NULL,
                           (rt_uint8_t *)&b_thread_stack[0],
                           sizeof(b_thread_stack),
                           6,
                           5);
                          
  
   /* init led thread */
   result = rt_thread_init(&c_thread,
                           "c_thread",
                           c_thread_entry,
                           RT_NULL,
                           (rt_uint8_t *)&c_thread_stack[0],
                           sizeof(c_thread_stack),
                           7,
                           5);
                          
   return 0;
}
/* 導(dǎo)出到 msh 命令列表中 */
MSH_CMD_EXPORT(pause_thread_init, pause thread);


審核編輯：湯梓紅