os_task.src

在51单片机上移植成功的UCOS-II操作系统源代码,包括源代码及相关注释

; *                       memory locations.  'pstk' MUST point to a valid 'free' data item.
; *
; *              prio     is the task's priority.  A unique priority MUST be assigned to each task and the
; *                       lower the number, the higher the priority.
; *
; *              id       is the task's ID (0..65535)
; *
; *              pbos     is a pointer to the task's bottom of stack.  If the configuration constant 
; *                       OS_STK_GROWTH is set to 1, the stack is assumed to grow downward (i.e. from high
; *                       memory to low memory).  'pbos' will thus point to the LOWEST (valid) memory 
; *                       location of the stack.  If OS_STK_GROWTH is set to 0, 'pbos' will point to the 
; *                       HIGHEST memory location of the stack and the stack will grow with increasing
; *                       memory locations.  'pbos' MUST point to a valid 'free' data item.
; *
; *              stk_size is the size of the stack in number of elements.  If OS_STK is set to INT8U,
; *                       'stk_size' corresponds to the number of bytes available.  If OS_STK is set to
; *                       INT16U, 'stk_size' contains the number of 16-bit entries available.  Finally, if
; *                       OS_STK is set to INT32U, 'stk_size' contains the number of 32-bit entries
; *                       available on the stack.
; *
; *              pext     is a pointer to a user supplied memory location which is used as a TCB extension.
; *                       For example, this user memory can hold the contents of floating-point registers
; *                       during a context switch, the time each task takes to execute, the number of times
; *                       the task has been switched-in, etc. 
; *
; *              opt      contains additional information (or options) about the behavior of the task.  The 
; *                       LOWER 8-bits are reserved by uC/OS-II while the upper 8 bits can be application 
; *                       specific.  See OS_TASK_OPT_??? in uCOS-II.H.
; *
; * Returns    : OS_NO_ERR        if the function was successful.
; *              OS_PRIO_EXIT     if the task priority already exist 
; *                               (each task MUST have a unique priority).
; *              OS_PRIO_INVALID  if the priority you specify is higher that the maximum allowed 
; *                               (i.e. > OS_LOWEST_PRIO)
; *********************************************************************************************************
; */
; /*$PAGE*/
; #if   OS_TASK_CREATE_EXT_EN    
; INT8U OSTaskCreateExt (void   (*task)(void *pd), 
;                        void    *ppdata, 
;                        OS_STK  *ptos, 
;                        INT8U    prio,
;                        INT16U   id,
;                        OS_STK  *pbos,
;                        INT32U   stk_size,
;                        void    *pext,
;                        INT16U   opt) reentrant
; {
;     void    *psp;
;     INT8U    err;
;     INT16U   i;
;     OS_STK  *pfill;
; 
; 
;     if (prio > OS_LOWEST_PRIO) {             /* Make sure priority is within allowable range           */
;         return (OS_PRIO_INVALID);
;     }
;     OS_ENTER_CRITICAL();
;     if (OSTCBPrioTbl[prio] == (OS_TCB *)0) { /* Make sure task doesn't already exist at this priority  */
;         OSTCBPrioTbl[prio] = (OS_TCB *)1;    /* Reserve the priority to prevent others from doing ...  */
;                                              /* ... the same thing until task is created.              */
;         OS_EXIT_CRITICAL();
;         
;         if (opt & OS_TASK_OPT_STK_CHK) {     /* See if stack checking has been enabled                 */
;             if (opt & OS_TASK_OPT_STK_CLR) { /* See if stack needs to be cleared                       */
;                 pfill = pbos;                /* Yes, fill the stack with zeros                         */
;                 for (i = 0; i < stk_size; i++) {
;                     #if OS_STK_GROWTH == 1
;                     *pfill++ = (OS_STK)0;
;                     #else
;                     *pfill-- = (OS_STK)0;
;                     #endif
;                 }
;             }
;         }
;         
;         psp = (void *)OSTaskStkInit(task, ppdata, ptos, opt); /* Initialize the task's stack            */
;         err = OSTCBInit(prio, psp, pbos, id, stk_size, pext, opt);         
;         if (err == OS_NO_ERR) {
;             OS_ENTER_CRITICAL();
;             OSTaskCtr++;                                     /* Increment the #tasks counter           */
;             OSTaskCreateHook(OSTCBPrioTbl[prio]);            /* Call user defined hook                 */
;             OS_EXIT_CRITICAL();
;             if (OSRunning) {                 /* Find highest priority task if multitasking has started */
;                 OSSched();
;             }
;         } else {
;             OS_ENTER_CRITICAL();
;             OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority available to others                 */
;             OS_EXIT_CRITICAL();
;         }
;         return (err);
;     } else {
;         OS_EXIT_CRITICAL();
;         return (OS_PRIO_EXIST);
;     }
; }
; #endif
; /*$PAGE*/
; /*
; *********************************************************************************************************
; *                                            DELETE A TASK
; *
; * Description: This function allows you to delete a task.  The calling task can delete itself by 
; *              its own priority number.  The deleted task is returned to the dormant state and can be
; *              re-activated by creating the deleted task again.
; *
; * Arguments  : prio    is the priority of the task to delete.  Note that you can explicitely delete
; *                      the current task without knowing its priority level by setting 'prio' to
; *                      OS_PRIO_SELF.
; *
; * Returns    : OS_NO_ERR           if the call is successful
; *              OS_TASK_DEL_IDLE    if you attempted to delete uC/OS-II's idle task
; *              OS_PRIO_INVALID     if the priority you specify is higher that the maximum allowed 
; *                                  (i.e. >= OS_LOWEST_PRIO) or, you have not specified OS_PRIO_SELF.
; *              OS_TASK_DEL_ERR     if the task you want to delete does not exist
; *              OS_TASK_DEL_ISR     if you tried to delete a task from an ISR
; *
; * Notes      : 1) To reduce interrupt latency, OSTaskDel() 'disables' the task:
; *                    a) by making it not ready
; *                    b) by removing it from any wait lists
; *                    c) by preventing OSTimeTick() from making the task ready to run.
; *                 The task can then be 'unlinked' from the miscellaneous structures in uC/OS-II.
; *              2) The function OSDummy() is called after OS_EXIT_CRITICAL() because, on most processors, 
; *                 the next instruction following the enable interrupt instruction is ignored.  You can 
; *                 replace OSDummy() with a macro that basically executes a NO OP (i.e. OS_NOP()).  The 
; *                 NO OP macro would avoid the execution time of the function call and return.
; *              3) An ISR cannot delete a task.
; *              4) The lock nesting counter is incremented because, for a brief instant, if the current
; *                 task is being deleted, the current task would not be able to be rescheduled because it
; *                 is removed from the ready list.  Incrementing the nesting counter prevents another task
; *                 from being schedule.  This means that the ISR would return to the current task which is
; *                 being deleted.  The rest of the deletion would thus be able to be completed.
; *********************************************************************************************************
; */
; /*$PAGE*/
; #if OS_TASK_DEL_EN
; INT8U OSTaskDel (INT8U prio) reentrant
; {
;     OS_TCB   *ptcb;
;     OS_EVENT *pevent;
; 
; 
;     if (prio == OS_IDLE_PRIO) {                                 /* Not allowed to delete idle task     */
;         return (OS_TASK_DEL_IDLE);
;     }
;     if (prio >= OS_LOWEST_PRIO && prio != OS_PRIO_SELF) {       /* Task priority valid ?               */
;         return (OS_PRIO_INVALID);
;     }
;     OS_ENTER_CRITICAL();
;     if (OSIntNesting > 0) {                                     /* See if trying to delete from ISR    */
;         OS_EXIT_CRITICAL();
;         return (OS_TASK_DEL_ISR);
;     }
;     if (prio == OS_PRIO_SELF) {                                 /* See if requesting to delete self    */
;         prio = OSTCBCur->OSTCBPrio;                             /* Set priority to delete to current   */
;     }
;     if ((ptcb = OSTCBPrioTbl[prio]) != (OS_TCB *)0) {           /* Task to delete must exist           */
;         if ((OSRdyTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0) {/* Make task not ready                 */
;             OSRdyGrp &= ~ptcb->OSTCBBitY;
;         }
;         if ((pevent = ptcb->OSTCBEventPtr) != (OS_EVENT *)0) {  /* If task is waiting on event         */
;             if ((pevent->OSEventTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0) { /* ... remove task from */
;                 pevent->OSEventGrp &= ~ptcb->OSTCBBitY;                        /* ... event ctrl block */
;             }
;         }
;         ptcb->OSTCBDly  = 0;                                    /* Prevent OSTimeTick() from updating  */
;         ptcb->OSTCBStat = OS_STAT_RDY;                          /* Prevent task from being resumed     */
;         OSLockNesting++;
;         OS_EXIT_CRITICAL();                                     /* Enabling INT. ignores next instruc. */
;         OSDummy();                                              /* ... Dummy ensures that INTs will be */
;         OS_ENTER_CRITICAL();                                    /* ... disabled HERE!                  */
;         OSLockNesting--;
;         OSTaskDelHook(ptcb);                                    /* Call user defined hook              */
;         OSTaskCtr--;                                            /* One less task being managed         */
;         OSTCBPrioTbl[prio] = (OS_TCB *)0;                       /* Clear old priority entry            */
;         if (ptcb->OSTCBPrev == (OS_TCB *)0) {                   /* Remove from TCB chain               */
;             ptcb->OSTCBNext->OSTCBPrev = (OS_TCB *)0;
;             OSTCBList                  = ptcb->OSTCBNext;
;         } else {
;             ptcb->OSTCBPrev->OSTCBNext = ptcb->OSTCBNext;
;             ptcb->OSTCBNext->OSTCBPrev = ptcb->OSTCBPrev;
;         }
;         ptcb->OSTCBNext = OSTCBFreeList;                        /* Return TCB to free TCB list         */
;         OSTCBFreeList   = ptcb;
;         OS_EXIT_CRITICAL();
;         OSSched();                                              /* Find new highest priority task      */
;         return (OS_NO_ERR);
;     } else {
;         OS_EXIT_CRITICAL();
;         return (OS_TASK_DEL_ERR);
;     }
; }
; #endif
; /*$PAGE*/
; /*
; *********************************************************************************************************
; *                                    REQUEST THAT A TASK DELETE ITSELF
; *
; * Description: This function is used to:
; *                   a) notify a task to delete itself.
; *                   b) to see if a task requested that the current task delete itself.
; *              This function is a little tricky to understand.  Basically, you have a task that needs
; *              to be deleted however, this task has resources that it has allocated (memory buffers,
; *              semaphores, mailboxes, queues etc.).  The task cannot be deleted otherwise these
; *              resources would not be freed.  The requesting task calls OSTaskDelReq() to indicate that
; *              the task needs to be deleted.  Deleting of the task is however, deferred to the task to
; *              be deleted.  For example, suppose that task #10 needs to be deleted.  The requesting task
; *              example, task #5, would call OSTaskDelReq(10).  When task #10 gets to execute, it calls
; *              this function by specifying OS_PRIO_SELF and monitors the returned value.  If the return
; *              value is OS_TASK_DEL_REQ, another task requested a task delete.  Task #10 would look like
; *              this:
; *
; *                   void Task(void *data)
; *                   {
; *                       .
; *                       .
; *                       while (1) {
; *                           OSTimeDly(1);
; *                           if (OSTaskDelReq(OS_PRIO_SELF) == OS_TASK_DEL_REQ) {
; *                               Release any owned resources;
; *                               De-allocate any dynamic memory;
; *                               OSTaskDel(OS_PRIO_SELF);
; *                           }
; *                       }
; *                   }
; *
; * Arguments  : prio    is the priority of the task to request the delete from
; *
; * Returns    : OS_NO_ERR          if the task exist and the request has been registered
; *              OS_TASK_NOT_EXIST  if the task has been deleted.  This allows the caller to know whether
; *                                 the request has been executed.
; *              OS_TASK_DEL_IDLE   if you requested to delete uC/OS-II's idle task
; *              OS_PRIO_INVALID    if the priority you specify is higher that the maximum allowed 
; *                                 (i.e. >= OS_LOWEST_PRIO) or, you have not specified OS_PRIO_SELF.
; *              OS_TASK_DEL_REQ    if a task (possibly another task) requested that the running task be 
; *                                 deleted.
; *********************************************************************************************************
; */
; /*$PAGE*/
; #if OS_TASK_DEL_EN
; INT8U OSTaskDelReq (INT8U prio) reentrant
; {
;     BOOLEAN  stat;
;     INT8U    err;
;     OS_TCB  *ptcb;
; 
; 
;     if (prio == OS_IDLE_PRIO) {                                 /* Not allowed to delete idle task     */
;         return (OS_TASK_DEL_IDLE);
;     }
;     if (prio >= OS_LOWEST_PRIO && prio != OS_PRIO_SELF) {       /* Task priority valid ?               */
;         return (OS_PRIO_INVALID);
;     }
;     if (prio == OS_PRIO_SELF) {                                 /* See if a task is requesting to ...  */
;         OS_ENTER_CRITICAL();                                    /* ... this task to delete itself      */
;         stat = OSTCBCur->OSTCBDelReq;                           /* Return request status to caller     */
;         OS_EXIT_CRITICAL();
;         return (stat);
;     } else {
;         OS_ENTER_CRITICAL();
;         if ((ptcb = OSTCBPrioTbl[prio]) != (OS_TCB *)0) {       /* Task to delete must exist           */
;             ptcb->OSTCBDelReq = OS_TASK_DEL_REQ;                /* Set flag indicating task to be DEL. */
;             err               = OS_NO_ERR;
;         } else {
;             err               = OS_TASK_NOT_EXIST;              /* Task must be deleted                */
;         }
;         OS_EXIT_CRITICAL();
;         return (err);
;     }
; }
; #endif
; /*$PAGE*/
; /*
; *********************************************************************************************************
; *                                        RESUME A SUSPENDED TASK
; *
; * Description: This function is called to resume a previously suspended task.  This is the only call that
; *              will remove an explicit task suspension.
; *
; * Arguments  : prio     is the priority of the task to resume.
; *
; * Returns    : OS_NO_ERR                if the requested task is resumed
; *              OS_PRIO_INVALID          if the priority you specify is higher that the maximum allowed 
; *                                       (i.e. >= OS_LOWEST_PRIO)
; *              OS_TASK_RESUME_PRIO      if the task to resume does not exist
; *              OS_TASK_NOT_SUSPENDED    if the task to resume has not been suspended
; *********************************************************************************************************
; */
; 
; #if OS_TASK_SUSPEND_EN
; INT8U OSTaskResume (INT8U prio) reentrant
; {
;     OS_TCB   *ptcb;
; 
; 
;     if (prio >= OS_LOWEST_PRIO) {                               /* Make sure task priority is valid    */
;         return (OS_PRIO_INVALID);
;     }
;     OS_ENTER_CRITICAL();
;     if ((ptcb = OSTCBPrioTbl[prio]) == (OS_TCB *)0) {           /* Task to suspend must exist          */
;         OS_EXIT_CRITICAL();
;         return (OS_TASK_RESUME_PRIO);
;     } else {
;         if (ptcb->OSTCBStat & OS_STAT_SUSPEND) {                           /* Task must be suspended   */
;             if (((ptcb->OSTCBStat &= ~OS_STAT_SUSPEND) == OS_STAT_RDY) &&  /* Remove suspension        */
;                  (ptcb->OSTCBDly  == 0)) {                                 /* Must not be delayed      */
;                 OSRdyGrp               |= ptcb->OSTCBBitY;                 /* Make task ready to run   */
;                 OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
;                 OS_EXIT_CRITICAL();
;                 OSSched();
;             } else {
;                 OS_EXIT_CRITICAL();
;             }
;             return (OS_NO_ERR);
;         } else {