os_mutex.c

操作系统ucosii的源码

*
* Note(s)    : 1) This function must be used with care.  Tasks that would normally expect the presence of
*                 the mutex MUST check the return code of OSMutexPend().
*
*              2) This call can potentially disable interrupts for a long time.  The interrupt disable
*                 time is directly proportional to the number of tasks waiting on the mutex.
*
*              3) Because ALL tasks pending on the mutex will be readied, you MUST be careful because the
*                 resource(s) will no longer be guarded by the mutex.
*
*              4) IMPORTANT: In the 'OS_DEL_ALWAYS' case, we assume that the owner of the Mutex (if there
*                            is one) is ready-to-run and is thus NOT pending on another kernel object or
*                            has delayed itself.  In other words, if a task owns the mutex being deleted,
*                            that task will be made ready-to-run at its original priority.
*********************************************************************************************************
*/

#if OS_MUTEX_DEL_EN
OS_EVENT  *OSMutexDel (OS_EVENT *pevent, INT8U opt, INT8U *err)
{
    BOOLEAN    tasks_waiting;
    OS_EVENT  *pevent_return;
    INT8U      pip;                                        /* Priority inheritance priority            */
    INT8U      prio;
    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 ((OS_EVENT *)0);
    }
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */
        *err = OS_ERR_PEVENT_NULL;
        return ((OS_EVENT *)0);
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {      /* Validate event block type                */
        *err = OS_ERR_EVENT_TYPE;
        return (pevent);
    }
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */
        *err = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */
        return (pevent);
    }
    OS_ENTER_CRITICAL();
    if (pevent->OSEventGrp != 0) {                         /* See if any tasks waiting on mutex        */
        tasks_waiting = OS_TRUE;                           /* Yes                                      */
    } else {
        tasks_waiting = OS_FALSE;                          /* No                                       */
    }
    switch (opt) {
        case OS_DEL_NO_PEND:                               /* DELETE MUTEX ONLY IF NO TASK WAITING --- */
             if (tasks_waiting == OS_FALSE) {
#if OS_EVENT_NAME_SIZE > 1
                 pevent->OSEventName[0] = '?';             /* Unknown name                             */
                 pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
                 pip                 = (INT8U)(pevent->OSEventCnt >> 8);
                 OSTCBPrioTbl[pip]   = (OS_TCB *)0;        /* Free up the PIP                          */
                 pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
                 pevent->OSEventPtr  = OSEventFreeList;    /* Return Event Control Block to free list  */
                 pevent->OSEventCnt  = 0;
                 OSEventFreeList     = pevent;
                 OS_EXIT_CRITICAL();
                 *err                = OS_NO_ERR;
                 pevent_return       = (OS_EVENT *)0;      /* Mutex has been deleted                   */
             } else {
                 OS_EXIT_CRITICAL();
                 *err                = OS_ERR_TASK_WAITING;
                 pevent_return       = pevent;
             }
             break;

        case OS_DEL_ALWAYS:                                /* ALWAYS DELETE THE MUTEX ---------------- */
             pip  = (INT8U)(pevent->OSEventCnt >> 8);                     /* Get PIP of mutex          */
             prio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /* Get owner's original prio */
             ptcb = (OS_TCB *)pevent->OSEventPtr;
             if (ptcb != (OS_TCB *)0) {                    /* See if any task owns the mutex           */
                 if (ptcb->OSTCBPrio == pip) {             /* See if original prio was changed         */
                     OSMutex_RdyAtPrio(ptcb, prio);        /* Yes, Restore the task's original prio    */
                 }
             }
             while (pevent->OSEventGrp != 0) {             /* Ready ALL tasks waiting for mutex        */
                 (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MUTEX);
             }
#if OS_EVENT_NAME_SIZE > 1
             pevent->OSEventName[0] = '?';                 /* Unknown name                             */
             pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
             pip                 = (INT8U)(pevent->OSEventCnt >> 8);
             OSTCBPrioTbl[pip]   = (OS_TCB *)0;            /* Free up the PIP                          */
             pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
             pevent->OSEventPtr  = OSEventFreeList;        /* Return Event Control Block to free list  */
             pevent->OSEventCnt  = 0;
             OSEventFreeList     = pevent;                 /* Get next free event control block        */
             OS_EXIT_CRITICAL();
             if (tasks_waiting == OS_TRUE) {               /* Reschedule only if task(s) were waiting  */
                 OS_Sched();                               /* Find highest priority task ready to run  */
             }
             *err          = OS_NO_ERR;
             pevent_return = (OS_EVENT *)0;                /* Mutex has been deleted                   */
             break;

        default:
             OS_EXIT_CRITICAL();
             *err          = OS_ERR_INVALID_OPT;
             pevent_return = pevent;
             break;
    }
    return (pevent_return);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                  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.
*                               OS_ERR_PIP_LOWER   If the priority of the task that owns the Mutex is
*                                                  HIGHER (i.e. a lower number) than the PIP.  This error
*                                                  indicates that you did not set the PIP higher (lower
*                                                  number) than ALL the tasks that compete for the Mutex.
*                                                  Unfortunately, this is something that could not be
*                                                  detected when the Mutex is created because we don't know
*                                                  what tasks will be using the Mutex.
*
* Returns    : none
*
* Note(s)    : 1) The task that owns the Mutex MUST NOT pend on any other event while it owns the mutex.
*
*              2) You MUST NOT change the priority of the task that owns the mutex
*********************************************************************************************************
*/
void  OSMutexPend (OS_EVENT *pevent, INT16U timeout, INT8U *err)
{
    INT8U      pip;                                        /* Priority Inheritance Priority (PIP)      */
    INT8U      mprio;                                      /* Mutex owner priority                     */
    BOOLEAN    rdy;                                        /* Flag indicating task was ready           */
    OS_TCB    *ptcb;
    OS_EVENT  *pevent2;
    INT8U      y;
#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 (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */
        *err = OS_ERR_PEVENT_NULL;
        return;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {      /* Validate event block type                */
        *err = OS_ERR_EVENT_TYPE;
        return;
    }
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */
        *err = OS_ERR_PEND_ISR;                            /* ... can't PEND from an ISR               */
        return;
    }
    if (OSLockNesting > 0) {                               /* See if called with scheduler locked ...  */
        *err = OS_ERR_PEND_LOCKED;                         /* ... can't PEND when locked               */
        return;
    }
    OS_ENTER_CRITICAL();                                
    pip = (INT8U)(pevent->OSEventCnt >> 8);                /* Get PIP from mutex                       */
                                                           /* 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       */
        if (OSTCBCur->OSTCBPrio <= pip) {                  /*      PIP 'must' have a SMALLER prio ...  */
            OS_EXIT_CRITICAL();                            /*      ... than current task!              */
            *err  = OS_ERR_PIP_LOWER;
        } else {
            OS_EXIT_CRITICAL();
            *err  = OS_NO_ERR;
        }
        return;
    }
    mprio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /* No, Get priority of mutex owner   */
    ptcb  = (OS_TCB *)(pevent->OSEventPtr);                       /*     Point to TCB of mutex owner   */
    if (ptcb->OSTCBPrio > pip) {                                  /*     Need to promote prio of owner?*/
        if (mprio > OSTCBCur->OSTCBPrio) {
            y = ptcb->OSTCBY;
            if ((OSRdyTbl[y] & ptcb->OSTCBBitX) != 0) {           /*     See if mutex owner is ready   */
                OSRdyTbl[y] &= ~ptcb->OSTCBBitX;                  /*     Yes, Remove owner from Rdy ...*/
                if (OSRdyTbl[y] == 0) {                           /*          ... list at current prio */
                    OSRdyGrp &= ~ptcb->OSTCBBitY;
                }
                rdy = OS_TRUE;
            } else {
                pevent2 = ptcb->OSTCBEventPtr;
                if (pevent2 != (OS_EVENT *)0) {                   /* Remove from event wait list       */
                    if ((pevent2->OSEventTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0) {
                        pevent2->OSEventGrp &= ~ptcb->OSTCBBitY;
                    }
                }
                rdy = OS_FALSE;                            /* No                                       */
            }
            ptcb->OSTCBPrio = pip;                         /* Change owner task prio to PIP            */
#if OS_LOWEST_PRIO <= 63
            ptcb->OSTCBY    = (INT8U)( ptcb->OSTCBPrio >> 3);
            ptcb->OSTCBX    = (INT8U)( ptcb->OSTCBPrio & 0x07);
            ptcb->OSTCBBitY = (INT8U)(1 << ptcb->OSTCBY);