os_sem.c

UCOS-III

*
* Description: This function sets the semaphore count to the value specified as an argument.  Typically, this value
*              would be 0 but of course, we can set the semaphore to any value.
*
*              You would typically use this function when a semaphore is used as a signaling mechanism
*              and, you want to reset the count value.
*
* Arguments  : p_sem     is a pointer to the semaphore
*
*              cnt       is the new value for the semaphore count.  You would pass 0 to reset the semaphore count.
*
*              p_err     is a pointer to a variable that will contain an error code returned by this function.
*
*                            OS_ERR_NONE           The call was successful and the semaphore value was set.
*                            OS_ERR_OBJ_PTR_NULL   If 'p_sem' is a NULL pointer.
*                            OS_ERR_OBJ_TYPE       If 'p_sem' is not pointing to a semaphore.
*                            OS_ERR_TASK_WAITING   If tasks are waiting on the semaphore.
*
* Returns    : None
************************************************************************************************************************
*/

#if OS_CFG_SEM_SET_EN > 0u
void  OSSemSet (OS_SEM      *p_sem,
                OS_SEM_CTR   cnt,
                OS_ERR      *p_err)
{
    OS_PEND_LIST  *p_pend_list;
    CPU_SR_ALLOC();



#ifdef OS_SAFETY_CRITICAL
    if (p_err == (OS_ERR *)0) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return;
    }
#endif

#if OS_CFG_CALLED_FROM_ISR_CHK_EN > 0u
    if (OSIntNestingCtr > (OS_NESTING_CTR)0) {              /* Can't call this function from an ISR                   */
       *p_err = OS_ERR_SET_ISR;
        return;
    }
#endif

#if OS_CFG_ARG_CHK_EN > 0u
    if (p_sem == (OS_SEM *)0) {                             /* Validate 'p_sem'                                       */
        *p_err = OS_ERR_OBJ_PTR_NULL;
        return;
    }
#endif

#if OS_CFG_OBJ_TYPE_CHK_EN > 0u
    if (p_sem->Type != OS_OBJ_TYPE_SEM) {                   /* Make sure semaphore was created                        */
        *p_err = OS_ERR_OBJ_TYPE;
        return;
    }
#endif

    *p_err = OS_ERR_NONE;
    CPU_CRITICAL_ENTER();
    if (p_sem->Ctr > (OS_SEM_CTR)0) {                       /* See if semaphore already has a count                   */
        p_sem->Ctr = cnt;                                   /* Yes, set it to the new value specified.                */
    } else {
        p_pend_list = &p_sem->PendList;                     /* No                                                     */
        if (p_pend_list->NbrEntries == (OS_OBJ_QTY)0) {     /*      See if task(s) waiting?                           */
            p_sem->Ctr = cnt;                               /*      No, OK to set the value                           */
        } else {
            *p_err     = OS_ERR_TASK_WAITING;
        }
    }
    CPU_CRITICAL_EXIT();
}
#endif

/*$PAGE*/
/*
************************************************************************************************************************
*                                           CLEAR THE CONTENTS OF A SEMAPHORE
*
* Description: This function is called by OSSemDel() to clear the contents of a semaphore
*

* Argument(s): p_sem      is a pointer to the semaphore to clear
*              -----
*
* Returns    : none
*
* Note(s)    : 1) This function is INTERNAL to uC/OS-III and your application MUST NOT call it.
************************************************************************************************************************
*/

void  OS_SemClr (OS_SEM  *p_sem)
{
    p_sem->Type    = OS_OBJ_TYPE_NONE;                      /* Mark the data structure as a NONE                      */
    p_sem->Ctr     = (OS_SEM_CTR)0;                         /* Set semaphore value                                    */
    p_sem->TS      = (CPU_TS    )0;                         /* Clear the time stamp                                   */
    p_sem->NamePtr = (CPU_CHAR *)((void *)"?SEM");
    OS_PendListInit(&p_sem->PendList);                      /* Initialize the waiting list                            */
}

/*$PAGE*/
/*
************************************************************************************************************************
*                                        ADD/REMOVE SEMAPHORE TO/FROM DEBUG LIST
*
* Description: These functions are called by uC/OS-III to add or remove a semaphore to/from the debug list.
*
* Arguments  : p_sem     is a pointer to the semaphore to add/remove
*
* Returns    : none
*
* Note(s)    : These functions are INTERNAL to uC/OS-III and your application should not call it.
************************************************************************************************************************
*/


#if OS_CFG_DBG_EN > 0u
void  OS_SemDbgListAdd (OS_SEM  *p_sem)
{
    p_sem->DbgNamePtr               = (CPU_CHAR *)((void *)" ");
    p_sem->DbgPrevPtr               = (OS_SEM   *)0;
    if (OSSemDbgListPtr == (OS_SEM *)0) {
        p_sem->DbgNextPtr           = (OS_SEM   *)0;
    } else {
        p_sem->DbgNextPtr           =  OSSemDbgListPtr;
        OSSemDbgListPtr->DbgPrevPtr =  p_sem;
    }
    OSSemDbgListPtr                 =  p_sem;
}



void  OS_SemDbgListRemove (OS_SEM  *p_sem)
{
    OS_SEM  *p_sem_next;
    OS_SEM  *p_sem_prev;


    p_sem_prev = p_sem->DbgPrevPtr;
    p_sem_next = p_sem->DbgNextPtr;

    if (p_sem_prev == (OS_SEM *)0) {
        OSSemDbgListPtr = p_sem_next;
        if (p_sem_next != (OS_SEM *)0) {
            p_sem_next->DbgPrevPtr = (OS_SEM *)0;
        }
        p_sem->DbgNextPtr = (OS_SEM *)0;

    } else if (p_sem_next == (OS_SEM *)0) {
        p_sem_prev->DbgNextPtr = (OS_SEM *)0;
        p_sem->DbgPrevPtr      = (OS_SEM *)0;

    } else {
        p_sem_prev->DbgNextPtr =  p_sem_next;
        p_sem_next->DbgPrevPtr =  p_sem_prev;
        p_sem->DbgNextPtr      = (OS_SEM *)0;
        p_sem->DbgPrevPtr      = (OS_SEM *)0;
    }
}
#endif

/*$PAGE*/
/*
************************************************************************************************************************
*                                                SEMAPHORE INITIALIZATION
*
* Description: This function is called by OSInit() to initialize the semaphore management.
*

* Argument(s): p_err        is a pointer to a variable that will contain an error code returned by this function.
*
*                                OS_ERR_NONE     the call was successful
*
* Returns    : none
*
* Note(s)    : 1) This function is INTERNAL to uC/OS-III and your application MUST NOT call it.
************************************************************************************************************************
*/

void  OS_SemInit (OS_ERR  *p_err)
{
#ifdef OS_SAFETY_CRITICAL
    if (p_err == (OS_ERR *)0) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return;
    }
#endif

#if OS_CFG_DBG_EN > 0u
    OSSemDbgListPtr = (OS_SEM *)0;
#endif

    OSSemQty        = (OS_OBJ_QTY)0;
    *p_err          = OS_ERR_NONE;
}

/*$PAGE*/
/*
************************************************************************************************************************
*                                                 POST TO A SEMAPHORE
*
* Description: This function signals a semaphore
*
* Arguments  : p_sem    is a pointer to the semaphore
*
*              opt      determines the type of POST performed:
*
*                           OS_OPT_POST_1            POST to a single waiting task
*                           OS_OPT_POST_ALL          POST to ALL tasks that are waiting on the semaphore
*
*                           OS_OPT_POST_NO_SCHED     Do not call the scheduler
*
*                           Note(s): 1) OS_OPT_POST_NO_SCHED can be added with one of the other options.
*
*              ts       is a timestamp indicating when the post occurred.
*
*              p_err    is a pointer to a variable that will contain an error code returned by this function.
*
*                           OS_ERR_NONE          The call was successful and the semaphore was signaled.
*                           OS_ERR_OBJ_PTR_NULL  If 'p_sem' is a NULL pointer.
*                           OS_ERR_OBJ_TYPE      If 'p_sem' is not pointing at a semaphore
*                           OS_ERR_SEM_OVF       If the post would cause the semaphore count to overflow.
*
* Returns    : The current value of the semaphore counter or 0 upon error.
*
* Note(s)    : This function is INTERNAL to uC/OS-III and your application should not call it.
************************************************************************************************************************
*/

OS_SEM_CTR  OS_SemPost (OS_SEM  *p_sem,
                        OS_OPT   opt,
                        CPU_TS   ts,
                        OS_ERR  *p_err)
{
    OS_OBJ_QTY     cnt;
    OS_SEM_CTR     ctr;
    OS_PEND_LIST  *p_pend_list;
    OS_PEND_DATA  *p_pend_data;
    OS_PEND_DATA  *p_pend_data_next;
    OS_TCB        *p_tcb;
    CPU_SR_ALLOC();



    CPU_CRITICAL_ENTER();
    p_pend_list = &p_sem->PendList;
    if (p_pend_list->NbrEntries == (OS_OBJ_QTY)0) {         /* Any task waiting on semaphore?                         */
        switch (sizeof(OS_SEM_CTR)) {
            case 1u:
                 if (p_sem->Ctr == DEF_INT_08U_MAX_VAL) {
                     CPU_CRITICAL_EXIT();
                     *p_err = OS_ERR_SEM_OVF;
                     return ((OS_SEM_CTR)0);
                 }
                 break;

            case 2u:
                 if (p_sem->Ctr == DEF_INT_16U_MAX_VAL) {
                     CPU_CRITICAL_EXIT();
                     *p_err = OS_ERR_SEM_OVF;
                     return ((OS_SEM_CTR)0);
                 }
                 break;

            case 4u:
                 if (p_sem->Ctr == DEF_INT_32U_MAX_VAL) {
                     CPU_CRITICAL_EXIT();
                     *p_err = OS_ERR_SEM_OVF;
                     return ((OS_SEM_CTR)0);
                 }
                 break;

            default:
                 break;
        }
        p_sem->Ctr++;                                       /* No                                                     */
        ctr       = p_sem->Ctr;
        p_sem->TS = ts;                                     /* Save timestamp in semaphore control block              */
        CPU_CRITICAL_EXIT();
        *p_err    = OS_ERR_NONE;
        return (ctr);
    }

    OS_CRITICAL_ENTER_CPU_CRITICAL_EXIT();
    if ((opt & OS_OPT_POST_ALL) != (OS_OPT)0) {             /* Post message to all tasks waiting?                     */
        cnt = p_pend_list->NbrEntries;                      /* Yes                                                    */
    } else {
        cnt = (OS_OBJ_QTY)1;                                /* No                                                     */
    }
    p_pend_data = p_pend_list->HeadPtr;
    while (cnt > 0u) {
        p_tcb            = p_pend_data->TCBPtr;
        p_pend_data_next = p_pend_data->NextPtr;
        OS_Post((OS_PEND_OBJ *)((void *)p_sem),
                p_tcb,
                (void      *)0,
                (OS_MSG_SIZE)0,
                ts);
        p_pend_data = p_pend_data_next;
        cnt--;
    }
    ctr = p_sem->Ctr;
    OS_CRITICAL_EXIT_NO_SCHED();
    if ((opt & OS_OPT_POST_NO_SCHED) == (OS_OPT)0) {
        OSSched();                                          /* Run the scheduler                                      */
    }
    *p_err = OS_ERR_NONE;
    return (ctr);
}

#endif