www.pudn.com > uCOS-IIVC.rar > os_sem.c, change:2005-03-14,size:23523b


/* 
********************************************************************************************************* 
*                                                uC/OS-II 
*                                          The Real-Time Kernel 
*                                          SEMAPHORE MANAGEMENT 
* 
*                          (c) Copyright 1992-2005, Jean J. Labrosse, Weston, FL 
*                                           All Rights Reserved 
* 
* File    : OS_SEM.C 
* By      : Jean J. Labrosse 
* Version : V2.80 
********************************************************************************************************* 
*/ 
 
#ifndef  OS_MASTER_FILE 
#include <ucos_ii.h> 
#endif 
 
#if OS_SEM_EN > 0 
/* 
********************************************************************************************************* 
*                                           ACCEPT SEMAPHORE 
* 
* Description: This function checks the semaphore to see if a resource is available or, if an event 
*              occurred.  Unlike OSSemPend(), OSSemAccept() does not suspend the calling task if the 
*              resource is not available or the event did not occur. 
* 
* Arguments  : pevent     is a pointer to the event control block 
* 
* Returns    : >  0       if the resource is available or the event did not occur the semaphore is 
*                         decremented to obtain the resource. 
*              == 0       if the resource is not available or the event did not occur or, 
*                         if 'pevent' is a NULL pointer or, 
*                         if you didn't pass a pointer to a semaphore 
********************************************************************************************************* 
*/ 
 
#if OS_SEM_ACCEPT_EN > 0 
INT16U  OSSemAccept (OS_EVENT *pevent) 
{ 
    INT16U     cnt; 
#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 (pevent == (OS_EVENT *)0) {                    /* Validate 'pevent'                             */ 
        return (0); 
    } 
#endif 
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM) {   /* Validate event block type                     */ 
        return (0); 
    } 
    OS_ENTER_CRITICAL(); 
    cnt = pevent->OSEventCnt; 
    if (cnt > 0) {                                    /* See if resource is available                  */ 
        pevent->OSEventCnt--;                         /* Yes, decrement semaphore and notify caller    */ 
    } 
    OS_EXIT_CRITICAL(); 
    return (cnt);                                     /* Return semaphore count                        */ 
} 
#endif 
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                           CREATE A SEMAPHORE 
* 
* Description: This function creates a semaphore. 
* 
* Arguments  : cnt           is the initial value for the semaphore.  If the value is 0, no resource is 
*                            available (or no event has occurred).  You initialize the semaphore to a 
*                            non-zero value to specify how many resources are available (e.g. if you have 
*                            10 resources, you would initialize the semaphore to 10). 
* 
* Returns    : != (void *)0  is a pointer to the event control clock (OS_EVENT) associated with the 
*                            created semaphore 
*              == (void *)0  if no event control blocks were available 
********************************************************************************************************* 
*/ 
 
OS_EVENT  *OSSemCreate (INT16U cnt) 
{ 
    OS_EVENT  *pevent; 
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */ 
    OS_CPU_SR  cpu_sr = 0; 
#endif 
 
 
 
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */ 
        return ((OS_EVENT *)0);                            /* ... can't CREATE from an ISR             */ 
    } 
    OS_ENTER_CRITICAL(); 
    pevent = OSEventFreeList;                              /* Get next free event control block        */ 
    if (OSEventFreeList != (OS_EVENT *)0) {                /* See if pool of free ECB pool was empty   */ 
        OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr; 
    } 
    OS_EXIT_CRITICAL(); 
    if (pevent != (OS_EVENT *)0) {                         /* Get an event control block               */ 
        pevent->OSEventType    = OS_EVENT_TYPE_SEM; 
        pevent->OSEventCnt     = cnt;                      /* Set semaphore value                      */ 
        pevent->OSEventPtr     = (void *)0;                /* Unlink from ECB free list                */ 
#if OS_EVENT_NAME_SIZE > 1 
        pevent->OSEventName[0] = '?';                      /* Unknown name                             */ 
        pevent->OSEventName[1] = OS_ASCII_NUL; 
#endif 
        OS_EventWaitListInit(pevent);                      /* Initialize to 'nobody waiting' on sem.   */ 
    } 
    return (pevent); 
} 
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                         DELETE A SEMAPHORE 
* 
* Description: This function deletes a semaphore and readies all tasks pending on the semaphore. 
* 
* Arguments  : pevent        is a pointer to the event control block associated with the desired 
*                            semaphore. 
* 
*              opt           determines delete options as follows: 
*                            opt == OS_DEL_NO_PEND   Delete semaphore ONLY if no task pending 
*                            opt == OS_DEL_ALWAYS    Deletes the semaphore even if tasks are waiting. 
*                                                    In this case, all the tasks pending will be readied. 
* 
*              err           is a pointer to an error code that can contain one of the following values: 
*                            OS_NO_ERR               The call was successful and the semaphore was deleted 
*                            OS_ERR_DEL_ISR          If you attempted to delete the semaphore from an ISR 
*                            OS_ERR_INVALID_OPT      An invalid option was specified 
*                            OS_ERR_TASK_WAITING     One or more tasks were waiting on the semaphore 
*                            OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a semaphore 
*                            OS_ERR_PEVENT_NULL      If 'pevent' is a NULL pointer. 
* 
* Returns    : pevent        upon error 
*              (OS_EVENT *)0 if the semaphore was successfully deleted. 
* 
* Note(s)    : 1) This function must be used with care.  Tasks that would normally expect the presence of 
*                 the semaphore MUST check the return code of OSSemPend(). 
*              2) OSSemAccept() callers will not know that the intended semaphore has been deleted unless 
*                 they check 'pevent' to see that it's a NULL pointer. 
*              3) 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 semaphore. 
*              4) Because ALL tasks pending on the semaphore will be readied, you MUST be careful in 
*                 applications where the semaphore is used for mutual exclusion because the resource(s) 
*                 will no longer be guarded by the semaphore. 
********************************************************************************************************* 
*/ 
 
#if OS_SEM_DEL_EN > 0 
OS_EVENT  *OSSemDel (OS_EVENT *pevent, INT8U opt, INT8U *err) 
{ 
    BOOLEAN    tasks_waiting; 
    OS_EVENT  *pevent_return; 
#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 (pevent); 
    } 
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */ 
        *err = OS_ERR_PEVENT_NULL; 
        return (pevent); 
    } 
#endif 
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM) {        /* 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 semaphore    */ 
        tasks_waiting = TRUE;                              /* Yes                                      */ 
    } else { 
        tasks_waiting = FALSE;                             /* No                                       */ 
    } 
    switch (opt) { 
        case OS_DEL_NO_PEND:                               /* Delete semaphore only if no task waiting */ 
             if (tasks_waiting == FALSE) { 
#if OS_EVENT_NAME_SIZE > 1 
                 pevent->OSEventName[0] = '?';             /* Unknown name                             */ 
                 pevent->OSEventName[1] = OS_ASCII_NUL; 
#endif 
                 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(); 
                 *err                   = OS_NO_ERR; 
                 pevent_return          = (OS_EVENT *)0;   /* Semaphore has been deleted               */ 
             } else { 
                 OS_EXIT_CRITICAL(); 
                 *err                   = OS_ERR_TASK_WAITING; 
                 pevent_return          = pevent; 
             } 
             break; 
 
        case OS_DEL_ALWAYS:                                /* Always delete the semaphore              */ 
             while (pevent->OSEventGrp != 0) {             /* Ready ALL tasks waiting for semaphore    */ 
                 (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_SEM); 
             } 
#if OS_EVENT_NAME_SIZE > 1 
             pevent->OSEventName[0] = '?';                 /* Unknown name                             */ 
             pevent->OSEventName[1] = OS_ASCII_NUL; 
#endif 
             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 == 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;       /* Semaphore has been deleted               */ 
             break; 
 
        default: 
             OS_EXIT_CRITICAL(); 
             *err                   = OS_ERR_INVALID_OPT; 
             pevent_return          = pevent; 
             break; 
    } 
    return (pevent_return); 
} 
#endif 
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                           PEND ON SEMAPHORE 
* 
* Description: This function waits for a semaphore. 
* 
* Arguments  : pevent        is a pointer to the event control block associated with the desired 
*                            semaphore. 
* 
*              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 
*                            semaphore or, until the resource becomes available (or the event occurs). 
* 
*              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 resource 
*                                                or, the event you are waiting for occurred. 
*                            OS_TIMEOUT          The semaphore was not received within the specified 
*                                                timeout. 
*                            OS_ERR_EVENT_TYPE   If you didn't pass a pointer to a semaphore. 
*                            OS_ERR_PEND_ISR     If you called this function from an ISR and the result 
*                                                would lead to a suspension. 
*                            OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer. 
* 
* Returns    : none 
********************************************************************************************************* 
*/ 
 
void  OSSemPend (OS_EVENT *pevent, INT16U timeout, INT8U *err) 
{ 
#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_SEM) {   /* 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; 
    } 
    OS_ENTER_CRITICAL(); 
    if (pevent->OSEventCnt > 0) {                     /* If sem. is positive, resource available ...   */ 
        pevent->OSEventCnt--;                         /* ... decrement semaphore only if positive.     */ 
        OS_EXIT_CRITICAL(); 
        *err = OS_NO_ERR; 
        return; 
    } 
                                                      /* Otherwise, must wait until event occurs       */ 
    OSTCBCur->OSTCBStat   |= OS_STAT_SEM;             /* Resource not available, pend on semaphore     */ 
    OSTCBCur->OSTCBPendTO  = FALSE; 
    OSTCBCur->OSTCBDly     = timeout;                 /* Store pend timeout in 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->OSTCBPendTO == TRUE) {              /* See if we timedout                            */ 
        OS_EventTO(pevent); 
        OS_EXIT_CRITICAL(); 
        *err = OS_TIMEOUT;                            /* Indicate that didn't get event within TO      */ 
        return; 
    } 
    OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0; 
    OS_EXIT_CRITICAL(); 
    *err = OS_NO_ERR; 
} 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                         POST TO A SEMAPHORE 
* 
* Description: This function signals a semaphore 
* 
* Arguments  : pevent        is a pointer to the event control block associated with the desired 
*                            semaphore. 
* 
* Returns    : OS_NO_ERR           The call was successful and the semaphore was signaled. 
*              OS_SEM_OVF          If the semaphore count exceeded its limit.  In other words, you have 
*                                  signalled the semaphore more often than you waited on it with either 
*                                  OSSemAccept() or OSSemPend(). 
*              OS_ERR_EVENT_TYPE   If you didn't pass a pointer to a semaphore 
*              OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer. 
********************************************************************************************************* 
*/ 
 
INT8U  OSSemPost (OS_EVENT *pevent) 
{ 
#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 (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */ 
        return (OS_ERR_PEVENT_NULL); 
    } 
#endif 
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM) {        /* Validate event block type                */ 
        return (OS_ERR_EVENT_TYPE); 
    } 
    OS_ENTER_CRITICAL(); 
    if (pevent->OSEventGrp != 0) {                             /* See if any task waiting for semaphore*/ 
        (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_SEM); /* Ready HPT waiting on event           */ 
        OS_EXIT_CRITICAL(); 
        OS_Sched();                                            /* Find HPT ready to run                */ 
        return (OS_NO_ERR); 
    } 
    if (pevent->OSEventCnt < 65535u) {                /* Make sure semaphore will not overflow         */ 
        pevent->OSEventCnt++;                         /* Increment semaphore count to register event   */ 
        OS_EXIT_CRITICAL(); 
        return (OS_NO_ERR); 
    } 
    OS_EXIT_CRITICAL();                               /* Semaphore value has reached its maximum       */ 
    return (OS_SEM_OVF); 
} 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                          QUERY A SEMAPHORE 
* 
* Description: This function obtains information about a semaphore 
* 
* Arguments  : pevent        is a pointer to the event control block associated with the desired 
*                            semaphore 
* 
*              p_sem_data    is a pointer to a structure that will contain information about the 
*                            semaphore. 
* 
* Returns    : OS_NO_ERR           The call was successful and the message was sent 
*              OS_ERR_EVENT_TYPE   If you are attempting to obtain data from a non semaphore. 
*              OS_ERR_PEVENT_NULL  If 'pevent'     is a NULL pointer. 
*              OS_ERR_PDATA_NULL   If 'p_sem_data' is a NULL pointer 
********************************************************************************************************* 
*/ 
 
#if OS_SEM_QUERY_EN > 0 
INT8U  OSSemQuery (OS_EVENT *pevent, OS_SEM_DATA *p_sem_data) 
{ 
#if OS_LOWEST_PRIO <= 63 
    INT8U     *psrc; 
    INT8U     *pdest; 
#else 
    INT16U    *psrc; 
    INT16U    *pdest; 
#endif 
    INT8U      i; 
#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 (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */ 
        return (OS_ERR_PEVENT_NULL); 
    } 
    if (p_sem_data == (OS_SEM_DATA *)0) {                  /* Validate 'p_sem_data'                    */ 
        return (OS_ERR_PDATA_NULL); 
    } 
#endif 
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM) {        /* Validate event block type                */ 
        return (OS_ERR_EVENT_TYPE); 
    } 
    OS_ENTER_CRITICAL(); 
    p_sem_data->OSEventGrp = pevent->OSEventGrp;           /* Copy message mailbox wait list           */ 
    psrc                   = &pevent->OSEventTbl[0]; 
    pdest                  = &p_sem_data->OSEventTbl[0]; 
    for (i = 0; i < OS_EVENT_TBL_SIZE; i++) { 
        *pdest++ = *psrc++; 
    } 
    p_sem_data->OSCnt = pevent->OSEventCnt;                /* Get semaphore count                      */ 
    OS_EXIT_CRITICAL(); 
    return (OS_NO_ERR); 
} 
#endif                                                     /* OS_SEM_QUERY_EN                          */ 
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                              SET SEMAPHORE 
* 
* Description: This function sets the semaphore count to the value specified as an argument.  Typically, 
*              this value would be 0. 
* 
*              You would typically use this function when a semaphore is used as a signaling mechanism 
*              and, you want to reset the count value. 
* 
* Arguments  : pevent     is a pointer to the event control block 
* 
*              cnt        is the new value for the semaphore count.  You would pass 0 to reset the 
*                         semaphore count. 
* 
*              err        is a pointer to an error code returned by the function as follows: 
* 
*                            OS_NO_ERR            The call was successful and the semaphore value was set. 
*                            OS_ERR_EVENT_TYPE    If you didn't pass a pointer to a semaphore. 
*                            OS_ERR_PEVENT_NULL   If 'pevent' is a NULL pointer. 
*                            OS_ERR_TASK_WAITING  If tasks are waiting on the semaphore. 
********************************************************************************************************* 
*/ 
 
#if OS_SEM_SET_EN > 0 
void  OSSemSet (OS_EVENT *pevent, INT16U cnt, INT8U *err) 
{ 
#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_SEM) {   /* Validate event block type                     */ 
        *err = OS_ERR_EVENT_TYPE; 
        return; 
    } 
    OS_ENTER_CRITICAL(); 
    *err = OS_NO_ERR; 
    if (pevent->OSEventCnt > 0) {                     /* See if semaphore already has a count          */ 
        pevent->OSEventCnt = cnt;                     /* Yes, set it to the new value specified.       */ 
    } else {                                          /* No                                            */ 
        if (pevent->OSEventGrp == 0) {                /*      See if task(s) waiting?                  */ 
            pevent->OSEventCnt = cnt;                 /*      No, OK to set the value                  */ 
        } else { 
            *err               = OS_ERR_TASK_WAITING; 
        } 
    } 
    OS_EXIT_CRITICAL(); 
} 
#endif 
 
#endif                                                /* OS_SEM_EN                                     */