μcosii源码试读8- OS_InitTaskIdle()；初始化idle任务

初始化idletask的代码如下

/*
*********************************************************************************************************
* INITIALIZATION
* CREATING THE IDLE TASK
*
* Description: This function creates the Idle Task.
*
* Arguments : none
*
* Returns : none
*********************************************************************************************************
*/

static void OS_InitTaskIdle (void)
{
#if OS_TASK_NAME_SIZE > 7
    INT8U err;
#endif


#if OS_TASK_CREATE_EXT_EN > 0
    #if OS_STK_GROWTH == 1
    (void)OSTaskCreateExt(OS_TaskIdle,
                          (void *)0, /* No arguments passed to OS_TaskIdle() */
                          &OSTaskIdleStk[OS_TASK_IDLE_STK_SIZE - 1], /* Set Top-Of-Stack */
                          OS_TASK_IDLE_PRIO, /* Lowest priority level */
                          OS_TASK_IDLE_ID,
                          &OSTaskIdleStk[0], /* Set Bottom-Of-Stack */
                          OS_TASK_IDLE_STK_SIZE,
                          (void *)0, /* No TCB extension */
                          OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);/* Enable stack checking + clear stack */
    #else
    (void)OSTaskCreateExt(OS_TaskIdle,
                          (void *)0, /* No arguments passed to OS_TaskIdle() */
                          &OSTaskIdleStk[0], /* Set Top-Of-Stack */
                          OS_TASK_IDLE_PRIO, /* Lowest priority level */
                          OS_TASK_IDLE_ID,
                          &OSTaskIdleStk[OS_TASK_IDLE_STK_SIZE - 1], /* Set Bottom-Of-Stack */
                          OS_TASK_IDLE_STK_SIZE,
                          (void *)0, /* No TCB extension */
                          OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);/* Enable stack checking + clear stack */
    #endif
#else
    #if OS_STK_GROWTH == 1
    (void)OSTaskCreate(OS_TaskIdle,
                       (void *)0,
                       &OSTaskIdleStk[OS_TASK_IDLE_STK_SIZE - 1],
                       OS_TASK_IDLE_PRIO);
    #else
    (void)OSTaskCreate(OS_TaskIdle,
                       (void *)0,
                       &OSTaskIdleStk[0],
                       OS_TASK_IDLE_PRIO);
    #endif
#endif

#if OS_TASK_NAME_SIZE > 14
    OSTaskNameSet(OS_TASK_IDLE_PRIO, (INT8U *)"uC/OS-II Idle", &err);
#else
#if OS_TASK_NAME_SIZE > 7
    OSTaskNameSet(OS_TASK_IDLE_PRIO, (INT8U *)"OS-Idle", &err);
#endif
#endif
}

设置一个字节大小的变量err

当系统可以创建OSTaskCreateExt()即用户可以额外的附加数据域的任务创建

并且OS_STK_GROWTH == 1即栈的地址是从高地址到低地址的

使用OSTaskCreateExt(OS_TaskIdle,
                          (void *)0,                 /* No arguments passed to OS_TaskIdle() */
                          &OSTaskIdleStk[OS_TASK_IDLE_STK_SIZE - 1], /* Set Top-Of-Stack    */
                          OS_TASK_IDLE_PRIO,                       /* Lowest priority level */
                          OS_TASK_IDLE_ID,
                          &OSTaskIdleStk[0],                         /* Set Bottom-Of-Stack  */
                          OS_TASK_IDLE_STK_SIZE,
                          (void *)0,                                 /* No TCB extension   */
                          OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);/* Enable stack checking + clear stack  */

 

创建idle任务，函数的9个参数分别为，任务代码的指针（任务函数名），pdata传递给任务的参数指针，

分配给任务的堆栈的栈顶指针，分配给任务的优先级数据，（之后是Ext后缀的任务创建函数才有的）

特殊id（目前版本未使用），栈底指针（用于堆栈的检验），

size用于指定堆栈的容量（如果栈的单位容量为4个字节，size为1000，那么栈的大小为4×1000个字节）

指向用户附加数据域的指针（附加的哦），最后，有三个选项，分别表示堆栈检验，堆栈清零和浮点操作的使能。

 

当使能HIGH-LOW栈的时候，堆栈的top指针指向数组最后一位，当LOW-HIGH时，堆栈的top指向数组头

数组的内存分配一定是从低地址向高地址，跟大端小端系统木有联系

 

如果Ext的使能没有打开，就是用(void)OSTaskCreate(OS_TaskIdle,
                       (void *)0,
                       &OSTaskIdleStk[OS_TASK_IDLE_STK_SIZE - 1],
                       OS_TASK_IDLE_PRIO);

创建任务，其参数与前面的ext函数的前四个参数含义相同，

 

创建完成后，如果OS_TASK_NAME_SIZE足够大，使用OSTaskNameSet函数设置taskname

/*
*********************************************************************************************************
* ASSIGN A NAME TO A TASK
*
* Description: This function is used to set the name of a task.
*
* Arguments : prio is the priority of the task that you want the assign a name to.
*
* pname is a pointer to an ASCII string that contains the name of the task. The ASCII
* string must be NUL terminated.
*
* err is a pointer to an error code that can contain one of the following values:
*
* OS_NO_ERR if the requested task is resumed
* OS_TASK_NOT_EXIST if the task has not been created or is assigned to a Mutex
* OS_ERR_TASK_NAME_TOO_LONG if the name you are giving to the task exceeds the
* storage capacity of a task name as specified by
* OS_TASK_NAME_SIZE.
* OS_ERR_PNAME_NULL You passed a NULL pointer for 'pname'
* OS_PRIO_INVALID if you specified an invalid priority:
* A higher value than the idle task or not OS_PRIO_SELF.
*
* Returns : None
*********************************************************************************************************
*/
#if OS_TASK_NAME_SIZE > 1
void OSTaskNameSet (INT8U prio, INT8U *pname, INT8U *err)
{
    INT8U len;
    OS_TCB *ptcb;
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (err == (INT8U *)0) { /* Validate 'err' */
        return;
    }
    if (prio > OS_LOWEST_PRIO) { /* Task priority valid ? */
        if (prio != OS_PRIO_SELF) {
            *err = OS_PRIO_INVALID; /* No */
            return;
        }
    }
    if (pname == (INT8U *)0) { /* Is 'pname' a NULL pointer? */
        *err = OS_ERR_PNAME_NULL; /* Yes */
        return;
    }
#endif
    OS_ENTER_CRITICAL();
    if (prio == OS_PRIO_SELF) { /* See if caller desires to set it's own name */
        prio = OSTCBCur->OSTCBPrio;
    }
    ptcb = OSTCBPrioTbl[prio];
    if (ptcb == (OS_TCB *)0) { /* Does task exist? */
        OS_EXIT_CRITICAL(); /* No */
        *err = OS_TASK_NOT_EXIST;
        return;
    }
    if (ptcb == (OS_TCB *)1) { /* Task assigned to a Mutex? */
        OS_EXIT_CRITICAL(); /* Yes */
        *err = OS_TASK_NOT_EXIST;
        return;
    }
    len = OS_StrLen(pname); /* Yes, Can we fit the string in the TCB? */
    if (len > (OS_TASK_NAME_SIZE - 1)) { /* No */
        OS_EXIT_CRITICAL();
        *err = OS_ERR_TASK_NAME_TOO_LONG;
        return;
    }
    (void)OS_StrCopy(ptcb->OSTCBTaskName, pname); /* Yes, copy to TCB */
    OS_EXIT_CRITICAL();
    *err = OS_NO_ERR;
}
#endif

设置必要的局部变量，设置参数

如果OS_ARG_CHK_EN > 0即使能变量检查位

idle的优先级一般被定义为OS_LOWEST_PRIO

那么检查指针参数是否指向空指针，检查优先级是否大于OS_LOWEST_PRIO

关中断

得到优先级，然后使用OSTCBPrioTbl[prio]函数返回prio优先级对应的任务TCB指针

如果为空，返回错误

求出strlen如果过长返回超出长度错误

一切ok使用OS_StrCopy(ptcb->OSTCBTaskName, pname);将字符串pname拷贝到TCB的taskname中去

开中断

err返回NO_ERR

/*
*********************************************************************************************************
* IDLE TASK
*
* Description: This task is internal to uC/OS-II and executes whenever no other higher priority tasks
* executes because they are ALL waiting for event(s) to occur.
*
* Arguments : none
*
* Returns : none
*
* Note(s) : 1) OSTaskIdleHook() is called after the critical section to ensure that interrupts will be
* enabled for at least a few instructions. On some processors (ex. Philips XA), enabling
* and then disabling interrupts didn't allow the processor enough time to have interrupts
* enabled before they were disabled again. uC/OS-II would thus never recognize
* interrupts.
* 2) This hook has been added to allow you to do such things as STOP the CPU to conserve
* power.
*********************************************************************************************************
*/

void OS_TaskIdle (void *p_arg)
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
    OS_CPU_SR cpu_sr = 0;
#endif



    (void)p_arg; /* Prevent compiler warning for not using 'parg' */
    for (;;) {
        OS_ENTER_CRITICAL();
        OSIdleCtr++;
        OS_EXIT_CRITICAL();
        OSTaskIdleHook(); /* Call user definable HOOK */
    }
}

TaskIdle的函数实现：

死循环：

关中断，idle计数器自加，开中断，用户自定义程序TaskIdleHook