• uC/OS-II互斥信号(OS_mutex)块


    /*
    *********************************************************************************************************
    *                                                uC/OS-II
    *                                          The Real-Time Kernel
    *                                  MUTUAL EXCLUSION SEMAPHORE MANAGEMENT
    *
    *                          (c) Copyright 1992-2002, 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.
    *********************************************************************************************************
    */
    //This  function checks the mutual exclusion semaphore to see if a resource is available.
    #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/排斥 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.
    *********************************************************************************************************
    */
    //创建一个互斥信号量
    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;

        //各种判断
        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);                            
        }
        //书包
        OSTCBPrioTbl[prio] = (OS_TCB *)1;                      /* Reserve the table entry                  */
        pevent             = OSEventFreeList;                  /* Get next free event control block        */
        //判断事件控制块是否可用
        if (pevent == (OS_EVENT *)0) {                         /* See if an ECB was available              */
            //还回去
            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);
        }
        //否则
        OSEventFreeList     = (OS_EVENT *)OSEventFreeList->OSEventPtr;   /* Adjust the free list           */
        OS_EXIT_CRITICAL();
        //类型是互斥信息号量--4
        pevent->OSEventType = OS_EVENT_TYPE_MUTEX;
        //把优先级左移动8位 且低8位标记为11111111OSEventCnt的高八位是prio 低八位是8个1
        pevent->OSEventCnt  = (prio << 8) | OS_MUTEX_AVAILABLE;/* Resource is available                    */
        //表示任务没有使用本次信号量
        pevent->OSEventPtr  = (void *)0;                       /* No task owning the mutex                 */
        //然后对事件控制块进行初始化
        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.
    *********************************************************************************************************
    */
    //删除一个互斥信号量0000opt删除的方式--类似于信号量的删除
    #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) {
            /* Delete mutex only if no task waiting     */
            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
    *********************************************************************************************************
    */
    //请求一个互斥信号量---timeout延时时间  This function waits for a mutual exclusion semaphore.
    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    
        //优先级继承优先级
        INT8U      pip;                                        /* Priority Inheritance Priority (PIP)      */
        INT8U      mprio;                                      /* Mutex owner priority                     */
        //任务是否就绪标志
        BOOLEAN    rdy;                                        /* Flag indicating task was ready           */
        OS_TCB    *ptcb;

        //是否在中断
        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
        //事件指针是否可用
        if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */
            *err = OS_ERR_PEVENT_NULL;
            return;
        }
        //是否是互斥信号量
        if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) {      /* Validate event block type                */
            *err = OS_ERR_EVENT_TYPE;
            return;
        }
    #endif
        OS_ENTER_CRITICAL();                                   /* Is Mutex available?                      */
        //查看互斥信号量有效
        //若有信号OSEventCnt的低八位是8个1 说明该信号量未被占用   与OS_MUTEX_KEEP_LOWER_8进行与 若为111111111
        if ((INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE) {
            //与OS_MUTEX_KEEP_UPPER_8保存到高八位
            //把低八位置0 表示资源被占用 这时OSEventCnt高八位为pip 低八位为0
            pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;       /*      Yes, Acquire the resource                */
            //这时OSEventCnt高八位为pip 低八位为任务的优先级
            pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;         /*      Save priority of owning task        */
            //OSEventPtr指向任务控制块
            pevent->OSEventPtr  = (void *)OSTCBCur;            /*      Point to owning task's OS_TCB       */
            OS_EXIT_CRITICAL();
            *err  = OS_NO_ERR;
            return;
        }
        //取出优先级继承优先级pip
        pip   = (INT8U)(pevent->OSEventCnt >> 8);                     /* No, Get PIP from mutex            */
        //否则信号量被占用--取出互斥信号量所有者的优先级 赋值给mprio
        mprio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /*     Get priority of mutex owner   */
        //取出互斥信号量所有者的tcb地址 赋值给ptcb
        ptcb  = (OS_TCB *)(pevent->OSEventPtr);                       /*     Point to TCB of mutex owner   */
        //判断当前的是否等觘cb优先级  且 请求的任务块大于当前的优先级
        if (ptcb->OSTCBPrio != pip && mprio > OSTCBCur->OSTCBPrio) {  /*     Need to promote prio of owner?*/
            //查看互斥信号量所有者是否就绪--若就绪
            if ((OSRdyTbl[ptcb->OSTCBY] & ptcb->OSTCBBitX) != 0x00) { /*     See if mutex owner is ready   */
                                                                      /*     Yes, Remove owner from Rdy ...*/
                  //是否在就绪表中取消互斥信号量所有者的就绪标志                                                    /*          ... list at current prio */
                if ((OSRdyTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0x00) {
                    //已取消---就直接把就绪组中对应置0
                    OSRdyGrp &= ~ptcb->OSTCBBitY;
                }
                //就绪
                rdy = TRUE;
            } else {
                rdy = FALSE;                                          /* No                                */
            }
            //对互斥信号量所有者做优先级升级,改变TCB中所有者关于优先级域
            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];
            //就绪
            if (rdy == TRUE) {                                 /* If task was ready at owner's priority ...*/
                //在就绪表和就绪组中重新提升后的优先级设置就绪标志
                OSRdyGrp               |= ptcb->OSTCBBitY;     /* ... make it ready at new priority.       */
                OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
            }
            //互斥信号量原来未就绪
            OSTCBPrioTbl[pip]       = (OS_TCB *)ptcb;
        }
        //完成对优先级升级,继续对本任务就绪操作--设置等待互斥信号量的标志
        OSTCBCur->OSTCBStat |= OS_STAT_MUTEX;             /* Mutex not available, pend current task        */
        //存储超时
        OSTCBCur->OSTCBDly   = timeout;                   /* Store timeout in current task's TCB           */
        //取消本任务就绪状态
        OS_EventTaskWait(pevent);                         /* Suspend task until event or timeout occurs    */
        OS_EXIT_CRITICAL();
        OS_Sched();                                        /* Find next highest priority task ready         */
        OS_ENTER_CRITICAL();
        //若延时时间到了
        if (OSTCBCur->OSTCBStat & OS_STAT_MUTEX) {        /* Must have timed out if still waiting for event*/
            //结束等待状态  转去执行延时时间到 的函数
            OS_EventTO(pevent);
            OS_EXIT_CRITICAL();
            *err = OS_TIMEOUT;                            /* Indicate that we didn't get mutex within TO   */
            return;
        }
        //否则把当前指针指向0
        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.
    *********************************************************************************************************
    */
    //发送互斥信号量---释放一个互斥信号量
    INT8U  OSMutexPost (OS_EVENT *pevent)
    {
    #if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
        OS_CPU_SR  cpu_sr;
    #endif    
        //优先级继承优先级
        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    */
        //获取原来任务的优先级
        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);
        }
        //如果本任务是由于继承机制提高的优先级----恢复原来的优先级
        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;
        }
        //先占优先级指针表中的pip项
        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         */
            //将事件等待表中的优先级最高任务就绪
            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;
            //OSEventPtr指向新的互斥信号量所有者的tcb
            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);
        }
        //没有任务等待互斥信号量时就运行到这
        //Mutex is now available   
        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.
    *********************************************************************************************************
    */
    //This function obtains information about a mutex  OS_MUTEX_DATA结构体  用于保存互斥信号量的 信息
    #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;
        //各种判断

        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;//可用的一个互斥信号量
        } 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                              */

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  • 原文地址:https://www.cnblogs.com/wxb20/p/6230842.html
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