ucos-ii之OSTaskChangePrio

 /*
*********************************************************************************************************
*                                        CHANGE PRIORITY OF A TASK
*
* Description: This function allows you to change the priority of a task dynamically.  Note that the new
*              priority MUST be available.
*
* Arguments  : oldp     is the old priority
*
*              newp     is the new priority
*
* Returns    : OS_ERR_NONE            is the call was successful
*              OS_ERR_PRIO_INVALID    if the priority you specify is higher that the maximum allowed
*                                     (i.e. >= OS_LOWEST_PRIO)
*              OS_ERR_PRIO_EXIST      if the new priority already exist.
*              OS_ERR_PRIO            there is no task with the specified OLD priority (i.e. the OLD task does
*                                     not exist.
*              OS_ERR_TASK_NOT_EXIST  if the task is assigned to a Mutex PIP.
*********************************************************************************************************
*/

#if OS_TASK_CHANGE_PRIO_EN > 0
INT8U  OSTaskChangePrio (INT8U oldprio, INT8U newprio)
{
#if OS_EVENT_EN
    OS_EVENT    *pevent;
#endif
    OS_TCB      *ptcb;
    INT8U        x;
    INT8U        y;
#if OS_LOWEST_PRIO <= 63
    INT8U        bitx;
    INT8U        bity;
#else
    INT16U       bitx;
    INT16U       bity;
#endif
    INT8U        y_old;
#if OS_CRITICAL_METHOD == 3
    OS_CPU_SR    cpu_sr = 0;                                    /* Storage for CPU status register     */ 存储
//存PRIMASK(除能所有的中断寄存器)——(当然了，不可屏蔽中断（NMI）才不甩它呢)状态的。
#endif

 

#if OS_ARG_CHK_EN > 0
    if (oldprio >= OS_LOWEST_PRIO) {//看看优先级在不在范围
        if (oldprio != OS_PRIO_SELF) {
            return (OS_ERR_PRIO_INVALID);
        }
    }
    if (newprio >= OS_LOWEST_PRIO) {
        return (OS_ERR_PRIO_INVALID);
    }
#endif
    OS_ENTER_CRITICAL();
    if (OSTCBPrioTbl[newprio] != (OS_TCB *)0) {                 /* New priority must not already exist */ 新优先级当然是没被其他任务用过的。所以是NULL的。用过了，就指向其他任务的tcb了，或者临时赋值1了。
        OS_EXIT_CRITICAL();
        return (OS_ERR_PRIO_EXIST);
    }
    if (oldprio == OS_PRIO_SELF) {                              /* See if changing self                *///优先级为0xff代表改变自己
        oldprio = OSTCBCur->OSTCBPrio;                          /* Yes, get priority                   */
//#define  OS_PRIO_SELF              0xFFu         也就是说0xFF这个优先级用来形容改变自己的优先级。
    }
    ptcb = OSTCBPrioTbl[oldprio];
    if (ptcb == (OS_TCB *)0) {                                  /* Does task to change exist?          */
        OS_EXIT_CRITICAL();                                     /* No, can't change its priority!      */
        return (OS_ERR_PRIO);
    }
    if (ptcb == OS_TCB_RESERVED) {                              /* Is task assigned to Mutex           */
//见<ucos-ii之OSTaskCreate> OS_TCB_RESERVED(是1)代表该优先级的任务tcb储存在OSTCBPrioTbl的位置
//被其他任务先占领了。只是还没指向被先占领的任务的tcb.也就是说该优先级已经被其他任务用了，你就不能再用了。
        OS_EXIT_CRITICAL();                                     /* No, can't change its priority!      */
        return (OS_ERR_TASK_NOT_EXIST);
    }
#if OS_LOWEST_PRIO <= 63
    y                     = (INT8U)(newprio >> 3);              /* Yes, compute new TCB fields         *///三位高，三位低。2三次方8
    x                     = (INT8U)(newprio & 0x07);
    bity                  = (INT8U)(1 << y);
    bitx                  = (INT8U)(1 << x);
#else
    y                     = (INT8U)((newprio >> 4) & 0x0F);//现在是四位高，四位低 //2四次方16
    x                     = (INT8U)( newprio & 0x0F);
    bity                  = (INT16U)(1 << y);
    bitx                  = (INT16U)(1 << x);
#endif

    OSTCBPrioTbl[oldprio] = (OS_TCB *)0;                        /* Remove TCB from old priority        */
/* Make this priority available to others                 */为0代表没用过，可以被用。
    OSTCBPrioTbl[newprio] = ptcb;                               /* Place pointer to TCB @ new priority */
    y_old                 = ptcb->OSTCBY;
//<uc/os_II优先级判定表OSUnMapTbl>讲诉了以下的如何设置OSRdyTbl和OSRdyGrp 
    if ((OSRdyTbl[y_old] & ptcb->OSTCBBitX) != 0) {             /* If task is ready make it not        */
        OSRdyTbl[y_old] &= ~ptcb->OSTCBBitX;
        if (OSRdyTbl[y_old] == 0) {
            OSRdyGrp &= ~ptcb->OSTCBBitY;
        }
        OSRdyGrp    |= bity;                                    /* Make new priority ready to run      */
        OSRdyTbl[y] |= bitx;
    }
#if OS_EVENT_EN
    pevent = ptcb->OSTCBEventPtr;
    if (pevent != (OS_EVENT *)0) {                              /* ... remove from event wait list     */
        pevent->OSEventTbl[y_old] &= ~ptcb->OSTCBBitX;
        if (pevent->OSEventTbl[y_old] == 0) {
            pevent->OSEventGrp &= ~ptcb->OSTCBBitY;
        }
        pevent->OSEventGrp    |= bity;                          /* Add new priority to wait list       */
        pevent->OSEventTbl[y] |= bitx;
    }
#endif
    ptcb->OSTCBPrio = newprio;                                  /* Set new task priority               */
    ptcb->OSTCBY    = y;
    ptcb->OSTCBX    = x;
    ptcb->OSTCBBitY = bity;
    ptcb->OSTCBBitX = bitx;
    OS_EXIT_CRITICAL();
    if (OSRunning == OS_TRUE) {
        OS_Sched();                                             /* Find new highest priority task      */
    }
    return (OS_ERR_NONE);
}
#endif