os_mutex.src

本文面向首次接触uC/OS-II的程序员

; *                            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)LG_REENTRANT
; {
; #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)LG_REENTRANT
; {
; #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)LG_REENTRANT
; {
; #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;