*                        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.  Current choices are:
*
*                        OS_TASK_OPT_STK_CHK      Stack checking to be allowed for the task
*                        OS_TASK_OPT_STK_CLR      Clear the stack when the task is created
*                        OS_TASK_OPT_SAVE_FP      If the CPU has floating-point registers, save them
*                                                 during a context switch.
*
* Returns    : OS_ERR_NONE             if the function was successful.
*              OS_PRIO_EXIT            if the task priority already exist
*                                      (each task MUST have a unique priority).
*              OS_ERR_PRIO_INVALID     if the priority you specify is higher that the maximum allowed
*                                      (i.e. > OS_LOWEST_PRIO)
*              OS_ERR_TASK_CREATE_ISR  if you tried to create a task from an ISR.
*********************************************************************************************************
*/
/*$PAGE*/
#if OS_TASK_CREATE_EXT_EN > 0
INT8U  OSTaskCreateExt (void   (*task)(void *p_arg),
                        void    *p_arg,
                        OS_STK  *ptos,
                        INT8U    prio,
                        INT16U   id,
                        OS_STK  *pbos,
                        INT32U   stk_size,
                        void    *pext,
                        INT16U   opt)
{
    OS_STK    *psp;
    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 (prio > OS_LOWEST_PRIO) {             /* Make sure priority is within allowable range           */
        return (OS_ERR_PRIO_INVALID);
    }
#endif
    OS_ENTER_CRITICAL();
    if (OSIntNesting > 0) {                  /* Make sure we don't create the task from within an ISR  */
        OS_EXIT_CRITICAL();
        return (OS_ERR_TASK_CREATE_ISR);
    }
    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();

        OS_TaskStkClr(pbos, stk_size, opt);                    /* Clear the task stack (if needed)     */

        psp = OSTaskStkInit(task, p_arg, ptos, opt);           /* Initialize the task's stack          */
        err = OS_TCBInit(prio, psp, pbos, id, stk_size, pext, opt);
        if (err == OS_ERR_NONE) {
            if (OSRunning == OS_TRUE) {                        /* Find HPT if multitasking has started */
                OS_Sched();
            }
        } else {
            OS_ENTER_CRITICAL();
            OSTCBPrioTbl[prio] = (OS_TCB *)0;                  /* Make this priority avail. to others  */
            OS_EXIT_CRITICAL();
        }
        return (err);
    }
    OS_EXIT_CRITICAL();
    return (OS_ERR_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_ERR_NONE             if the call is successful
*              OS_ERR_TASK_DEL_IDLE    if you attempted to delete uC/OS-II's idle task
*              OS_ERR_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_ERR_TASK_DEL         if the task is assigned to a Mutex PIP.   
*              OS_ERR_TASK_NOT_EXIST   if the task you want to delete does not exist.
*              OS_ERR_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 OS_Dummy() is called after OS_EXIT_CRITICAL() because, on most processors,
*                 the next instruction following the enable interrupt instruction is ignored.
*              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 an 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 > 0
INT8U  OSTaskDel (INT8U prio)
{
#if OS_EVENT_EN
    OS_EVENT     *pevent;
#endif
#if (OS_VERSION >= 251) && (OS_FLAG_EN > 0) && (OS_MAX_FLAGS > 0)
    OS_FLAG_NODE *pnode;
#endif
    OS_TCB       *ptcb;
    INT8U         y;
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR     cpu_sr = 0;
#endif



    if (OSIntNesting > 0) {                                     /* See if trying to delete from ISR    */
        return (OS_ERR_TASK_DEL_ISR);
    }
    if (prio == OS_TASK_IDLE_PRIO) {                            /* Not allowed to delete idle task     */
        return (OS_ERR_TASK_DEL_IDLE);
    }
#if OS_ARG_CHK_EN > 0
    if (prio >= OS_LOWEST_PRIO) {                               /* Task priority valid ?               */
        if (prio != OS_PRIO_SELF) {
            return (OS_ERR_PRIO_INVALID);
        }
    }
#endif

    OS_ENTER_CRITICAL();
    if (prio == OS_PRIO_SELF) {                                 /* See if requesting to delete self    */
        prio = OSTCBCur->OSTCBPrio;                             /* Set priority to delete to current   */
    }
    ptcb = OSTCBPrioTbl[prio];
    if (ptcb == (OS_TCB *)0) {                                  /* Task to delete must exist           */
        OS_EXIT_CRITICAL();
        return (OS_ERR_TASK_NOT_EXIST);
    }
    if (ptcb == (OS_TCB *)1) {                                  /* Must not be assigned to Mutex       */
        OS_EXIT_CRITICAL();
        return (OS_ERR_TASK_DEL);
    }
    y            =  ptcb->OSTCBY;
    OSRdyTbl[y] &= ~ptcb->OSTCBBitX;
    if (OSRdyTbl[y] == 0) {                                     /* Make task not ready                 */
        OSRdyGrp &= ~ptcb->OSTCBBitY;
    }
    
#if OS_EVENT_EN
    pevent = ptcb->OSTCBEventPtr;
    if (pevent != (OS_EVENT *)0) {                              /* If task is waiting on event         */
        pevent->OSEventTbl[y] &= ~ptcb->OSTCBBitX;
        if (pevent->OSEventTbl[y] == 0) {                       /* ... remove task from ...            */
            pevent->OSEventGrp &= ~ptcb->OSTCBBitY;             /* ... event ctrl block                */
        }
    }
#endif

#if (OS_VERSION >= 251) && (OS_FLAG_EN > 0) && (OS_MAX_FLAGS > 0)
    pnode = ptcb->OSTCBFlagNode;
    if (pnode != (OS_FLAG_NODE *)0) {                           /* If task is waiting on event flag    */
        OS_FlagUnlink(pnode);                                   /* Remove from wait list               */
    }
#endif

    ptcb->OSTCBDly      = 0;                                    /* Prevent OSTimeTick() from updating  */
    ptcb->OSTCBStat     = OS_STAT_RDY;                          /* Prevent task from being resumed     */
    ptcb->OSTCBStatPend = OS_STAT_PEND_OK;
    if (OSLockNesting < 255u) {                                 /* Make sure we don't context switch   */
        OSLockNesting++;
    }
    OS_EXIT_CRITICAL();                                         /* Enabling INT. ignores next instruc. */
    OS_Dummy();                                                 /* ... Dummy ensures that INTs will be */
    OS_ENTER_CRITICAL();                                        /* ... disabled HERE!                  */
    if (OSLockNesting > 0) {                                    /* Remove context switch lock          */
        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;
#if OS_TASK_NAME_SIZE > 1
    ptcb->OSTCBTaskName[0] = '?';                               /* Unknown name                        */
    ptcb->OSTCBTaskName[1] = OS_ASCII_NUL;
#endif
    OS_EXIT_CRITICAL();
    if (OSRunning == OS_TRUE) {
        OS_Sched();                                             /* Find new highest priority task      */
    }
    return (OS_ERR_NONE);
}
#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_ERR_TASK_DEL_REQ, another task requested a task delete.  Task #10 would look like
*              this:
*
*                   void Task(void *p_arg)
*                   {
*                       .
*                       .
*                       while (1) {
*                           OSTimeDly(1);
*                           if (OSTaskDelReq(OS_PRIO_SELF) == OS_ERR_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_ERR_NONE            if the task exist and the request has been registered
*              OS_ERR_TASK_NOT_EXIST  if the task has been deleted.  This allows the caller to know whether
*                                     the request has been executed.
*              OS_ERR_TASK_DEL        if the task is assigned to a Mutex.