20190927（8）RT-Thread 线程管理源码解读（5）启动/控制及相对重要的函数说明

男娘i 2023-08-17 16:04 20阅读 0赞

#### 目的： ####

1 根据源码讲解启动挂起的函数内容  
2 说明一些跟线程调用相关的函数

> RT\_THREAD\_INIT 线程通过调用函数 rt\_thread\_create/init() 进入到初始状态  
> RT\_THREAD\_READY 初始状态的线程通过调用函数 rt\_thread\_startup() 进入到就绪状态  
> RT\_THREAD\_RUNNING 就绪状态的线程被调度器调度后进入运行状态  
> RT\_THREAD\_SUSPEND 当处于运行状态的线程调用 rt\_thread\_delay()，rt\_sem\_take()，rt\_mutex\_take()，rt\_mb\_recv() 等函数或者获取不到资源时，将进入到挂起状态  
> RT\_THREAD\_CLOSE rt\_thread\_delete/detach() 函数，将更改为关闭状态; 而运行状态的线程，如果运行结束，就会在线程的最后部分执行 rt\_thread\_exit() 函数，也将状态更改为关闭状态

#define RT_EOK 0 /* 无错误 */ 
    #define RT_ERROR 1 /* 普通错误 */ 
    #define RT_ETIMEOUT 2 /* 超时错误 */ 
    #define RT_EFULL 3 /* 资源已满 */ 
    #define RT_EEMPTY 4 /* 无资源 */ 
    #define RT_ENOMEM 5 /* 无内存 */ 
    #define RT_ENOSYS 6 /* 系统不支持 */ 
    #define RT_EBUSY 7 /* 系统忙 */ 
    #define RT_EIO 8 /* IO 错误 */ 
    #define RT_EINTR 9 /* 中断系统调用 */ 
    #define RT_EINVAL 10 /* 非法参数 */

--------------------

#### 正文 ####

##### 1 启动线程 re\_thread\_startup() #####

/**
     * This function will start a thread and put it to system ready queue
     *
     * @param thread the thread to be started
     *
     * @return the operation status, RT_EOK on OK, -RT_ERROR on error
     */
    rt_err_t rt_thread_startup(rt_thread_t thread)
    {
        /* thread check */
        RT_ASSERT(thread != RT_NULL);
        RT_ASSERT((thread->stat & RT_THREAD_STAT_MASK) == RT_THREAD_INIT); //没做初始化的无法启动
        RT_ASSERT(rt_object_get_type((rt_object_t)thread) == RT_Object_Class_Thread);//确保线程类型的正确性
    
        /* set current priority to init priority */
        thread->current_priority = thread->init_priority; //启动时默认当前优先级为初始设定的优先级
    
        /* calculate priority attribute */
    #if RT_THREAD_PRIORITY_MAX > 32 
        thread->number      = thread->current_priority >> 3;            /* 5bit */
        thread->number_mask = 1L << thread->number;
        thread->high_mask   = 1L << (thread->current_priority & 0x07);  /* 3bit */
    #else
        thread->number_mask = 1L << thread->current_priority;
    #endif
    
        RT_DEBUG_LOG(RT_DEBUG_THREAD, ("startup a thread:%s with priority:%d\n",
                                       thread->name, thread->init_priority)); //打印日志
        /* change thread stat */
        thread->stat = RT_THREAD_SUSPEND; //进入挂起状态
        /* then resume it */
        rt_thread_resume(thread); //使线程恢复运行
        
        if (rt_thread_self() != RT_NULL) //该函数将返回当前线程的线程对象句柄
        {
            /* do a scheduling */
            rt_schedule();//该函数将执行一次调度。它将选择一个具有最高优先级的线程，然后切换运行
        }
    
        return RT_EOK;
    }
    RTM_EXPORT(rt_thread_startup);

--------------------

##### 2. rt\_thread\_control 线程控制 #####

/**
     * This function will control thread behaviors according to control command.
     *
     * @param thread the specified thread to be controlled
     * @param cmd the control command, which includes
     *  RT_THREAD_CTRL_CHANGE_PRIORITY for changing priority level of thread; //改变线程优先级
     *  RT_THREAD_CTRL_STARTUP for starting a thread; //启动线程
     *  RT_THREAD_CTRL_CLOSE for delete a thread; //删除线程
     *  RT_THREAD_CTRL_BIND_CPU for bind the thread to a CPU.//针对多核指定线程到特定CPU上
     * @param arg the argument of control command //命令参数
     *
     * @return RT_EOK
     */
    rt_err_t rt_thread_control(rt_thread_t thread, int cmd, void *arg)
    {
        register rt_base_t temp;
    
        /* thread check */
        RT_ASSERT(thread != RT_NULL);
        RT_ASSERT(rt_object_get_type((rt_object_t)thread) == RT_Object_Class_Thread);//判断对象类型是否符合要求
    
        switch (cmd)
        {
        case RT_THREAD_CTRL_CHANGE_PRIORITY:
            /* disable interrupt */
            temp = rt_hw_interrupt_disable(); //关闭中断
    
            /* for ready thread, change queue */
            if ((thread->stat & RT_THREAD_STAT_MASK) == RT_THREAD_READY) //确保线程处于就绪状态
            {
                /* remove thread from schedule queue first */
                rt_schedule_remove_thread(thread);//先将线程移出去
    
                /* change thread priority */
                thread->current_priority = *(rt_uint8_t *)arg;//修改优先级
    
                /* recalculate priority attribute */
    #if RT_THREAD_PRIORITY_MAX > 32
                thread->number      = thread->current_priority >> 3;            /* 5bit */
                thread->number_mask = 1 << thread->number;
                thread->high_mask   = 1 << (thread->current_priority & 0x07);   /* 3bit */
    #else
                thread->number_mask = 1 << thread->current_priority;
    #endif
    
                /* insert thread to schedule queue again */
                rt_schedule_insert_thread(thread);//重新加入
            }
            else
            {
                thread->current_priority = *(rt_uint8_t *)arg;
    
                /* recalculate priority attribute */
    #if RT_THREAD_PRIORITY_MAX > 32
                thread->number      = thread->current_priority >> 3;            /* 5bit */
                thread->number_mask = 1 << thread->number;
                thread->high_mask   = 1 << (thread->current_priority & 0x07);   /* 3bit */
    #else
                thread->number_mask = 1 << thread->current_priority;
    #endif
            }
    
            /* enable interrupt */
            rt_hw_interrupt_enable(temp);
            break;
    
        case RT_THREAD_CTRL_STARTUP:
            return rt_thread_startup(thread);
    
    #ifdef RT_USING_HEAP
        case RT_THREAD_CTRL_CLOSE:
            return rt_thread_delete(thread);
    #endif
    
    #ifdef RT_USING_SMP //多核处理器
        case RT_THREAD_CTRL_BIND_CPU:
        {
            rt_uint8_t cpu;
    
            if ((thread->stat & RT_THREAD_STAT_MASK) != RT_THREAD_INIT)
            {
                /* we only support bind cpu before started phase. */
                return RT_ERROR;
            }
    
            cpu = (rt_uint8_t)(size_t)arg;
            thread->bind_cpu = cpu > RT_CPUS_NR? RT_CPUS_NR : cpu; //指定CPU
            break;
        }
    #endif /*RT_USING_SMP*/
        default:
            break;
        }
    
        return RT_EOK;
    }
    RTM_EXPORT(rt_thread_control);

--------------------

##### 3. 其他线程使用相关函数 #####

> rt\_thread\_self() 获取当前线程句柄  
> rt\_thread\_yield() 让出CPU使用权，将自身移动到同级别链表尾部  
> rt\_thread\_schedule() 也是出让 CPU 使用权，但是区别是一不会移动至链表尾部，二如果没有比该线程高优先存在就继续执行任务  
> rt\_thread\_sleep() / delay() / mdelay() 线程睡眠  
> rt\_thread\_suspend() 线程挂起（用户最好不用）  
> rt\_thread\_resume() 恢复线程