pend-mutex.txt

ucos-ii中等待一个互斥信号mutex源码

*                                  PEND ON MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function waits for a mutual exclusion semaphore.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired
*                            mutex.
*
*              timeout       is an optional timeout period (in clock ticks).  If non-zero, your task will
*                            wait for the resource up to the amount of time specified by this argument.
*                            If you specify 0, however, your task will wait forever at the specified
*                            mutex or, until the resource becomes available.
*
*              err           is a pointer to where an error message will be deposited.  Possible error
*                            messages are:
*                               OS_NO_ERR          The call was successful and your task owns the mutex
*                               OS_TIMEOUT         The mutex was not available within the specified time.
*                               OS_ERR_EVENT_TYPE  If you didn't pass a pointer to a mutex
*                               OS_ERR_PEVENT_NULL 'pevent' is a NULL pointer
*                               OS_ERR_PEND_ISR    If you called this function from an ISR and the result
*                                                  would lead to a suspension.
*
* Returns    : none

*********************************************************************************************************
*/
void  OSMutexPend (OS_EVENT *pevent, INT16U timeout, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR  cpu_sr;
#endif    
    INT8U      pip;                                        /* Priority Inheritance Priority (PIP)      */
    INT8U      mprio;                                      /* Mutex owner priority                     */
    BOOLEAN    rdy;                                        /* Flag indicating task was ready           */
    OS_TCB    *ptcb;


    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */
        *err = OS_ERR_PEND_ISR;                            /* ... can't PEND from an ISR               */
        return;
    }
#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */
        *err = OS_ERR_PEVENT_NULL;
        return;
    }
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {      /* Validate event block type                */
        *err = OS_ERR_EVENT_TYPE;
        return;
    }
#endif
    OS_ENTER_CRITICAL();								   /* Is Mutex available?                      */
    if ((INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE) {
        pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;       /* Yes, Acquire the resource                */
        pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;         /*      Save priority of owning task        */
        pevent->OSEventPtr  = (void *)OSTCBCur;            /*      Point to owning task's OS_TCB       */
        OS_EXIT_CRITICAL();
        *err  = OS_NO_ERR;
        return;
    }
    pip   = (INT8U)(pevent->OSEventCnt >> 8);                     /* No, Get PIP from mutex            */
    mprio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /*     Get priority of mutex owner   */
    ptcb  = (OS_TCB *)(pevent->OSEventPtr);                       /*     Point to TCB of mutex owner   */
    if (ptcb->OSTCBPrio != pip && mprio > OSTCBCur->OSTCBPrio) {  /*     Need to promote prio of owner?*/
        if ((OSRdyTbl[ptcb->OSTCBY] & ptcb->OSTCBBitX) != 0x00) { /*     See if mutex owner is ready   */
                                                                  /*     Yes, Remove owner from Rdy ...*/
                                                                  /*          ... list at current prio */
            if ((OSRdyTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0x00) {
                OSRdyGrp &= ~ptcb->OSTCBBitY;
            }
            rdy = TRUE;
        } else {
            rdy = FALSE;                                          /* No                                */
        }
        ptcb->OSTCBPrio         = pip;                     /* Change owner task prio to PIP            */
        ptcb->OSTCBY            = ptcb->OSTCBPrio >> 3;
        ptcb->OSTCBBitY         = OSMapTbl[ptcb->OSTCBY];
        ptcb->OSTCBX            = ptcb->OSTCBPrio & 0x07;
        ptcb->OSTCBBitX         = OSMapTbl[ptcb->OSTCBX];
        if (rdy == TRUE) {                                 /* If task was ready at owner's priority ...*/
            OSRdyGrp               |= ptcb->OSTCBBitY;     /* ... make it ready at new priority.       */
            OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
        }
        OSTCBPrioTbl[pip]       = (OS_TCB *)ptcb;
    }
    OSTCBCur->OSTCBStat |= OS_STAT_MUTEX;             /* Mutex not available, pend current task        */
    OSTCBCur->OSTCBDly   = timeout;                   /* Store timeout in current task's TCB           */
    OS_EventTaskWait(pevent);                         /* Suspend task until event or timeout occurs    */
    OS_EXIT_CRITICAL();
    OS_Sched();                                        /* Find next highest priority task ready         */
    OS_ENTER_CRITICAL();
    if (OSTCBCur->OSTCBStat & OS_STAT_MUTEX) {        /* Must have timed out if still waiting for event*/
        OS_EventTO(pevent);
        OS_EXIT_CRITICAL();
        *err = OS_TIMEOUT;                            /* Indicate that we didn't get mutex within TO   */
        return;
    }
    OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0;
    OS_EXIT_CRITICAL();
    *err = OS_NO_ERR;
}