www.pudn.com > zlggui.rar > OS_MUTEX.C, change:2001-05-12,size:27913b


/* 
********************************************************************************************************* 
*                                                uC/OS-II 
*                                          The Real-Time Kernel 
*                                  MUTUAL EXCLUSION SEMAPHORE MANAGEMENT 
* 
*                          (c) Copyright 1992-2001, Jean J. Labrosse, Weston, FL 
*                                           All Rights Reserved 
* 
* File : OS_MUTEX.C 
* By   : Jean J. Labrosse 
********************************************************************************************************* 
*/ 
 
#ifndef  OS_MASTER_FILE 
#include "includes.h" 
#endif 
 
/* 
********************************************************************************************************* 
*                                            LOCAL CONSTANTS 
********************************************************************************************************* 
*/ 
 
#define  OS_MUTEX_KEEP_LOWER_8   0x00FF 
#define  OS_MUTEX_KEEP_UPPER_8   0xFF00 
 
#define  OS_MUTEX_AVAILABLE      0x00FF 
 
 
#if OS_MUTEX_EN > 0 
/* 
********************************************************************************************************* 
*                                   ACCEPT MUTUAL EXCLUSION SEMAPHORE 
* 
* Description: This  function checks the mutual exclusion semaphore to see if a resource is available. 
*              Unlike OSMutexPend(), OSMutexAccept() 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 
* 
*              err        is a pointer to an error code which will be returned to your application: 
*                            OS_NO_ERR          if the call was successful. 
*                            OS_ERR_EVENT_TYPE  if 'pevent' is not 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 
* 
* Returns    : == 1       if the resource is available, the mutual exclusion semaphore is acquired 
*              == 0       a) if the resource is not available 
*                         b) you didn't pass a pointer to a mutual exclusion semaphore 
*                         c) you called this function from an ISR 
* 
* Warning(s) : This function CANNOT be called from an ISR because mutual exclusion semaphores are 
*              intended to be used by tasks only. 
********************************************************************************************************* 
*/ 
 
#if OS_MUTEX_ACCEPT_EN > 0 
INT8U  OSMutexAccept (OS_EVENT *pevent, INT8U *err) 
{ 
#if OS_CRITICAL_METHOD == 3                            /* Allocate storage for CPU status register     */ 
    OS_CPU_SR  cpu_sr; 
#endif     
     
     
    if (OSIntNesting > 0) {                            /* Make sure it's not called from an ISR        */ 
        *err = OS_ERR_PEND_ISR; 
        return (0); 
    } 
#if OS_ARG_CHK_EN > 0 
    if (pevent == (OS_EVENT *)0) {                     /* Validate 'pevent'                            */ 
        *err = OS_ERR_PEVENT_NULL; 
        return (0); 
    } 
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {  /* Validate event block type                    */ 
        *err = OS_ERR_EVENT_TYPE; 
        return (0); 
    } 
#endif                                                      
    OS_ENTER_CRITICAL();							   /* Get value (0 or 1) of Mutex                  */ 
    if ((pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE) {      
        pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;   /*      Mask off LSByte (Acquire Mutex)         */ 
        pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;     /*      Save current task priority in LSByte    */ 
        pevent->OSEventPtr  = (void *)OSTCBCur;        /*      Link TCB of task owning Mutex           */ 
        OS_EXIT_CRITICAL(); 
        *err = OS_NO_ERR; 
        return (1); 
    } 
    OS_EXIT_CRITICAL(); 
    *err = OS_NO_ERR; 
    return (0); 
} 
#endif                                                      
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                  CREATE A MUTUAL EXCLUSION SEMAPHORE 
* 
* Description: This function creates a mutual exclusion semaphore. 
* 
* Arguments  : prio          is the priority to use when accessing the mutual exclusion semaphore.  In 
*                            other words, when the semaphore is acquired and a higher priority task 
*                            attempts to obtain the semaphore then the priority of the task owning the 
*                            semaphore is raised to this priority.  It is assumed that you will specify 
*                            a priority that is LOWER in value than ANY of the tasks competing for the 
*                            mutex. 
* 
*              err           is a pointer to an error code which will be returned to your application: 
*                               OS_NO_ERR           if the call was successful. 
*                               OS_ERR_CREATE_ISR   if you attempted to create a MUTEX from an ISR 
*                               OS_PRIO_EXIST       if a task at the priority inheritance priority 
*                                                   already exist. 
*                               OS_ERR_PEVENT_NULL  No more event control blocks available. 
*                               OS_PRIO_INVALID     if the priority you specify is higher that the  
*                                                   maximum allowed (i.e. > OS_LOWEST_PRIO) 
* 
* Returns    : != (void *)0  is a pointer to the event control clock (OS_EVENT) associated with the 
*                            created mutex. 
*              == (void *)0  if an error is detected. 
* 
* Note(s)    : 1) The LEAST significant 8 bits of '.OSEventCnt' are used to hold the priority number 
*                 of the task owning the mutex or 0xFF if no task owns the mutex. 
*              2) The MOST  significant 8 bits of '.OSEventCnt' are used to hold the priority number 
*                 to use to reduce priority inversion. 
********************************************************************************************************* 
*/ 
 
OS_EVENT  *OSMutexCreate (INT8U prio, INT8U *err) 
{ 
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */ 
    OS_CPU_SR  cpu_sr; 
#endif     
    OS_EVENT  *pevent; 
 
 
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */ 
        *err = OS_ERR_CREATE_ISR;                          /* ... can't CREATE mutex from an ISR       */ 
        return ((OS_EVENT *)0); 
    } 
#if OS_ARG_CHK_EN > 0 
    if (prio >= OS_LOWEST_PRIO) {                          /* Validate PIP                             */ 
        *err = OS_PRIO_INVALID; 
        return ((OS_EVENT *)0); 
    } 
#endif 
    OS_ENTER_CRITICAL(); 
    if (OSTCBPrioTbl[prio] != (OS_TCB *)0) {               /* Mutex priority must not already exist    */ 
        OS_EXIT_CRITICAL();                                /* Task already exist at priority ...       */ 
        *err = OS_PRIO_EXIST;                              /* ... inheritance priority                 */ 
        return ((OS_EVENT *)0);                             
    } 
    OSTCBPrioTbl[prio] = (OS_TCB *)1;                      /* Reserve the table entry                  */ 
    pevent             = OSEventFreeList;                  /* Get next free event control block        */ 
    if (pevent == (OS_EVENT *)0) {                         /* See if an ECB was available              */ 
        OSTCBPrioTbl[prio] = (OS_TCB *)0;                  /* No, Release the table entry              */ 
        OS_EXIT_CRITICAL(); 
        *err               = OS_ERR_PEVENT_NULL;           /* No more event control blocks             */ 
        return (pevent); 
    } 
    OSEventFreeList     = (OS_EVENT *)OSEventFreeList->OSEventPtr;   /* Adjust the free list           */ 
    OS_EXIT_CRITICAL(); 
    pevent->OSEventType = OS_EVENT_TYPE_MUTEX; 
    pevent->OSEventCnt  = (prio << 8) | OS_MUTEX_AVAILABLE;/* Resource is available                    */ 
    pevent->OSEventPtr  = (void *)0;                       /* No task owning the mutex                 */ 
    OS_EventWaitListInit(pevent); 
    *err                = OS_NO_ERR; 
    return (pevent); 
} 
 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                          DELETE A MUTEX 
* 
* Description: This function deletes a mutual exclusion semaphore and readies all tasks pending on the it. 
* 
* Arguments  : pevent        is a pointer to the event control block associated with the desired mutex. 
* 
*              opt           determines delete options as follows: 
*                            opt == OS_DEL_NO_PEND   Delete mutex ONLY if no task pending 
*                            opt == OS_DEL_ALWAYS    Deletes the mutex 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 mutex was deleted 
*                            OS_ERR_DEL_ISR          If you attempted to delete the MUTEX from an ISR 
*                            OS_ERR_INVALID_OPT      An invalid option was specified 
*                            OS_ERR_TASK_WAITING     One or more tasks were waiting on the mutex 
*                            OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a mutex 
*                            OS_ERR_PEVENT_NULL      If 'pevent' is a NULL pointer. 
* 
* Returns    : pevent        upon error 
*              (OS_EVENT *)0 if the mutex was successfully deleted. 
* 
* 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. 
********************************************************************************************************* 
*/ 
 
#if OS_MUTEX_DEL_EN 
OS_EVENT  *OSMutexDel (OS_EVENT *pevent, INT8U opt, INT8U *err) 
{ 
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */ 
    OS_CPU_SR  cpu_sr; 
#endif     
    BOOLEAN    tasks_waiting; 
    INT8U      pip; 
 
 
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */ 
        *err = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */ 
        return (pevent); 
    } 
#if OS_ARG_CHK_EN > 0 
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */ 
        *err = OS_ERR_PEVENT_NULL; 
        return ((OS_EVENT *)0); 
    } 
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {      /* Validate event block type                */ 
        *err = OS_ERR_EVENT_TYPE; 
        return (pevent); 
    } 
#endif 
    OS_ENTER_CRITICAL(); 
    if (pevent->OSEventGrp != 0x00) {                      /* See if any tasks waiting on mutex        */ 
        tasks_waiting = TRUE;                              /* Yes                                      */ 
    } else { 
        tasks_waiting = FALSE;                             /* No                                       */ 
    } 
    switch (opt) { 
        case OS_DEL_NO_PEND:                               /* Delete mutex only if no task waiting     */ 
             if (tasks_waiting == FALSE) { 
                 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  */ 
                 OSEventFreeList     = pevent; 
                 OS_EXIT_CRITICAL(); 
                 *err = OS_NO_ERR; 
                 return ((OS_EVENT *)0);                   /* Mutex has been deleted                   */ 
             } else { 
                 OS_EXIT_CRITICAL(); 
                 *err = OS_ERR_TASK_WAITING; 
                 return (pevent); 
             } 
 
        case OS_DEL_ALWAYS:                                /* Always delete the mutex                  */ 
             while (pevent->OSEventGrp != 0x00) {          /* Ready ALL tasks waiting for mutex        */ 
                 OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MUTEX); 
             } 
             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  */ 
             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; 
             return ((OS_EVENT *)0);                       /* Mutex has been deleted                   */ 
 
        default: 
             OS_EXIT_CRITICAL(); 
             *err = OS_ERR_INVALID_OPT; 
             return (pevent); 
    } 
} 
#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. 
* 
* 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) 
{ 
#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; 
} 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                  POST TO A MUTUAL EXCLUSION SEMAPHORE 
* 
* Description: This function signals a mutual exclusion semaphore 
* 
* Arguments  : pevent              is a pointer to the event control block associated with the desired 
*                                  mutex. 
* 
* Returns    : OS_NO_ERR               The call was successful and the mutex was signaled. 
*              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_POST_ISR         Attempted to post from an ISR (not valid for MUTEXes) 
*              OS_ERR_NOT_MUTEX_OWNER  The task that did the post is NOT the owner of the MUTEX. 
********************************************************************************************************* 
*/ 
 
INT8U  OSMutexPost (OS_EVENT *pevent) 
{ 
#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */ 
    OS_CPU_SR  cpu_sr; 
#endif     
    INT8U      pip;                                   /* Priority inheritance priority                 */ 
    INT8U      prio; 
 
 
    if (OSIntNesting > 0) {                           /* See if called from ISR ...                    */ 
        return (OS_ERR_POST_ISR);                     /* ... can't POST mutex from an ISR              */ 
    } 
#if OS_ARG_CHK_EN > 0 
    if (pevent == (OS_EVENT *)0) {                    /* Validate 'pevent'                             */ 
        return (OS_ERR_PEVENT_NULL); 
    } 
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) { /* Validate event block type                     */ 
        return (OS_ERR_EVENT_TYPE); 
    }                                                  
#endif 
    OS_ENTER_CRITICAL(); 
    pip  = (INT8U)(pevent->OSEventCnt >> 8);          /* Get priority inheritance priority of mutex    */ 
    prio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /* Get owner's original priority      */ 
    if (OSTCBCur->OSTCBPrio != pip &&  
        OSTCBCur->OSTCBPrio != prio) {                /* See if posting task owns the MUTEX            */ 
        OS_EXIT_CRITICAL(); 
        return (OS_ERR_NOT_MUTEX_OWNER); 
    } 
    if (OSTCBCur->OSTCBPrio == pip) {                 /* Did we have to raise current task's priority? */ 
                                                      /* Yes, Return to original priority              */ 
                                                      /*      Remove owner from ready list at 'pip'    */ 
        if ((OSRdyTbl[OSTCBCur->OSTCBY] &= ~OSTCBCur->OSTCBBitX) == 0) { 
            OSRdyGrp &= ~OSTCBCur->OSTCBBitY; 
        } 
        OSTCBCur->OSTCBPrio         = prio; 
        OSTCBCur->OSTCBY            = prio >> 3; 
        OSTCBCur->OSTCBBitY         = OSMapTbl[OSTCBCur->OSTCBY]; 
        OSTCBCur->OSTCBX            = prio & 0x07; 
        OSTCBCur->OSTCBBitX         = OSMapTbl[OSTCBCur->OSTCBX]; 
        OSRdyGrp                   |= OSTCBCur->OSTCBBitY; 
        OSRdyTbl[OSTCBCur->OSTCBY] |= OSTCBCur->OSTCBBitX; 
        OSTCBPrioTbl[prio]          = (OS_TCB *)OSTCBCur; 
    } 
    OSTCBPrioTbl[pip] = (OS_TCB *)1;                  /* Reserve table entry                           */ 
    if (pevent->OSEventGrp != 0x00) {                 /* Any task waiting for the mutex?               */ 
                                                      /* Yes, Make HPT waiting for mutex ready         */ 
        prio                = OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MUTEX); 
        pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;  /*      Save priority of mutex's new owner       */ 
        pevent->OSEventCnt |= prio; 
        pevent->OSEventPtr  = OSTCBPrioTbl[prio];     /*      Link to mutex owner's OS_TCB             */ 
        OS_EXIT_CRITICAL(); 
        OS_Sched();                                   /*      Find highest priority task ready to run  */ 
        return (OS_NO_ERR); 
    } 
    pevent->OSEventCnt |= OS_MUTEX_AVAILABLE;         /* No,  Mutex is now available                   */ 
    pevent->OSEventPtr  = (void *)0; 
    OS_EXIT_CRITICAL(); 
    return (OS_NO_ERR); 
} 
/*$PAGE*/ 
/* 
********************************************************************************************************* 
*                                     QUERY A MUTUAL EXCLUSION SEMAPHORE 
* 
* Description: This function obtains information about a mutex 
* 
* Arguments  : pevent        is a pointer to the event control block associated with the desired mutex 
* 
*              pdata         is a pointer to a structure that will contain information about the mutex 
* 
* Returns    : OS_NO_ERR            The call was successful and the message was sent 
*              OS_ERR_QUERY_ISR     If you called this function from an ISR 
*              OS_ERR_PEVENT_NULL   'pevent' is a NULL pointer 
*              OS_ERR_EVENT_TYPE    If you are attempting to obtain data from a non mutex. 
********************************************************************************************************* 
*/ 
 
#if OS_MUTEX_QUERY_EN > 0 
INT8U  OSMutexQuery (OS_EVENT *pevent, OS_MUTEX_DATA *pdata) 
{ 
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */ 
    OS_CPU_SR  cpu_sr; 
#endif     
    INT8U     *psrc; 
    INT8U     *pdest; 
 
 
    if (OSIntNesting > 0) {                                /* See if called from ISR ...               */ 
        return (OS_ERR_QUERY_ISR);                         /* ... can't QUERY mutex from an ISR        */ 
    } 
#if OS_ARG_CHK_EN > 0 
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */ 
        return (OS_ERR_PEVENT_NULL); 
    } 
    if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {      /* Validate event block type                */ 
        return (OS_ERR_EVENT_TYPE); 
    } 
#endif 
    OS_ENTER_CRITICAL(); 
    pdata->OSMutexPIP  = (INT8U)(pevent->OSEventCnt >> 8); 
    pdata->OSOwnerPrio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8); 
    if (pdata->OSOwnerPrio == 0xFF) { 
        pdata->OSValue = 1; 
    } else { 
        pdata->OSValue = 0; 
    } 
    pdata->OSEventGrp  = pevent->OSEventGrp;               /* Copy wait list                           */ 
    psrc               = &pevent->OSEventTbl[0]; 
    pdest              = &pdata->OSEventTbl[0]; 
#if OS_EVENT_TBL_SIZE > 0 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 1 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 2 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 3 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 4 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 5 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 6 
    *pdest++           = *psrc++; 
#endif 
 
#if OS_EVENT_TBL_SIZE > 7 
    *pdest             = *psrc; 
#endif 
    OS_EXIT_CRITICAL(); 
    return (OS_NO_ERR); 
} 
#endif                                                     /* OS_MUTEX_QUERY_EN                        */ 
#endif                                                     /* OS_MUTEX_EN                              */