原创浅析μC/OS-II v2.85内核OSTimeDly()函数工作原理

 2008-6-6 12:39  3426 8 8 分类: MCU/ 嵌入式

浅析μC/OS-II v2.85内核OSTimeDly()函数工作原理

文章来源:http://gliethttp.cublog.cn[转载请声明出处]

//----------------------------------------------------------------------
//1.OSTimeDly()函数
void OSTimeDly (INT16U ticks)
{
    INT8U y;
#if OS_CRITICAL_METHOD == 3
    OS_CPU_SR cpu_sr = 0;
#endif
    if (OSIntNesting > 0) {
        return;//在中断处理函数中调用了OSTimeDly(),那么直接退出
    }
    if (ticks > 0) {
        OS_ENTER_CRITICAL();
//调用OSTimeDly()的进程自己把自己从就绪控制矩阵中拿下来,
//即:去掉调度器(x,y)矩形阵列(OSRdyTbl,OSRdyGrp)中该task对应的bit位,使得调度器不考虑
//该task的调度
        y = OSTCBCur->OSTCBY;
        OSRdyTbl[y] &= ~OSTCBCur->OSTCBBitX;
        if (OSRdyTbl[y] == 0) {
            OSRdyGrp &= ~OSTCBCur->OSTCBBitY;
        }
//延时ticks值,放入OSTCBDly单元,在os时钟滴答处理函数OSTimeTick()中,会处理该单元[gliethttp]
        OSTCBCur->OSTCBDly = ticks;
        OS_EXIT_CRITICAL();
//因为本task正在运行,所以本task现在的优先级最高,现在本task已经将自己从就绪控制矩阵中--调度器(x,y)矩形阵列
//把自己摘掉,所以调度函数OS_Sched()一定会切换到另一个task中执行新task的代码[gliethttp]
        OS_Sched();//具体参见《浅析μC/OS-II v2.85内核调度函数》
    }//ticks==0,那么什么也不做
}
//----------------------------------------------------------------------
//2.OSTimeTick()--在定时中断里引用的系统滴答函数
void OSTimeTick (void)
{
    OS_TCB *ptcb;
#if OS_TICK_STEP_EN > 0
    BOOLEAN step;
#endif
#if OS_CRITICAL_METHOD == 3
    OS_CPU_SR cpu_sr = 0;//该3方式将使中断状态寄存器放入堆栈中

#endif

#if OS_TIME_TICK_HOOK_EN > 0
    OSTimeTickHook();
#endif
#if OS_TIME_GET_SET_EN > 0
    OS_ENTER_CRITICAL();
    OSTime++;
    OS_EXIT_CRITICAL();
#endif
    if (OSRunning == OS_TRUE) {
#if OS_TICK_STEP_EN > 0
//控制内核的tick
        switch (OSTickStepState) {
            case OS_TICK_STEP_DIS:
                 step = OS_TRUE;
                 break;
            case OS_TICK_STEP_WAIT:
                 step = OS_FALSE;
                 break;
            case OS_TICK_STEP_ONCE:
//本次tick将将影响到task的OSTCBDly域
//但以后的tick将一直被屏蔽,不会影响到OSTCBDly域
//直到外部将OSTickStepState改变为止[gliethttp]
                 step = OS_TRUE;
                 OSTickStepState = OS_TICK_STEP_WAIT;
                 break;
            default:
                 step = OS_TRUE;//本次tick将影响到task的OSTCBDly域
                 OSTickStepState = OS_TICK_STEP_DIS;
                 break;
        }
        if (step == OS_FALSE) {
            return;
        }
#endif
        ptcb = OSTCBList;
//2007-09-08 gliethttp
//OSTCBList是一个按进程创建的先后顺序链接成的task单向链表,最后创建的task在最前面,最先创建的
//task在单向链表的尾端,
//所以OS_TaskIdle空闲进程在链表的最后,因为它最先创建
        while (ptcb->OSTCBPrio != OS_TASK_IDLE_PRIO) {
            OS_ENTER_CRITICAL();
            if (ptcb->OSTCBDly != 0) {
                if (--ptcb->OSTCBDly == 0) {
//该task的延时时间已到,解析此次延时是OSTimeDly()引起的,还是OSQPend()之类超时引起的[gliethttp]
                    if ((ptcb->OSTCBStat & OS_STAT_PEND_ANY) != OS_STAT_RDY) {
                        //2007-09-08 gliethttp
                        //如:由OSSemPend (pevent,timeout,perr);定义的timeout已经到了,对应task需要运行了
                        //超时时间到,所以不论当前进程是在做什么,只要时间一到
                        //该task就可以运行了,所以清除所有事件标志,之后状态标示为OS_STAT_PEND_TO(超时)
                        ptcb->OSTCBStat &= ~(INT8U)OS_STAT_PEND_ANY;
                        ptcb->OSTCBStatPend = OS_STAT_PEND_TO;//超时异常
                    } else {
                        //2007-09-08 gliethttp
                        //说明该task调用的是OSTimeDly()
                        ptcb->OSTCBStatPend = OS_STAT_PEND_OK;//正常结束
                    }
                    if ((ptcb->OSTCBStat & OS_STAT_SUSPEND) == OS_STAT_RDY) {
                        //2007-09-08 gliethttp
                        //如果该task没有suspend,那么把当前就绪的task加入到运行调度器的就绪控制矩阵中
                        //等待被调度
                        OSRdyGrp |= ptcb->OSTCBBitY;
                        OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
                    }
                }
            }
            ptcb = ptcb->OSTCBNext;//继续运算下一个task的OSTCBDly时间域
            OS_EXIT_CRITICAL();
        }
    }
}