📄 os_task.c
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* 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_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)
* OS_ERR_TASK_CREATE_ISR if you tried to create a task from an ISR.
*********************************************************************************************************
*/
/*$PAGE*/
#if OS_TASK_CREATE_EXT_EN > 0
INT8U OSTaskCreateExt (void (*task)(void *pd),
void *p_arg,
OS_STK *ptos,
INT8U prio,
INT16U id,
OS_STK *pbos,
INT32U stk_size,
void *pext,
INT16U opt)
{
OS_STK *psp;
INT8U err;
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
cpu_sr = 0; /* Prevent compiler warning */
#endif
#if OS_ARG_CHK_EN > 0
if (prio > OS_LOWEST_PRIO) { /* Make sure priority is within allowable range */
return (OS_PRIO_INVALID);
}
#endif
OS_ENTER_CRITICAL();
if (OSIntNesting > 0) { /* Make sure we don't create the task from within an ISR */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_CREATE_ISR);
}
if (OSTCBPrioTbl[prio] == (OS_TCB *)0) { /* Make sure task doesn't already exist at this priority */
OSTCBPrioTbl[prio] = (OS_TCB *)1; /* Reserve the priority to prevent others from doing ... */
/* ... the same thing until task is created. */
OS_EXIT_CRITICAL();
OS_TaskStkClr(pbos, stk_size, opt); /* Clear the task stack (if needed) */
psp = (OS_STK *)OSTaskStkInit(task, p_arg, ptos, opt); /* Initialize the task's stack */
err = OS_TCBInit(prio, psp, pbos, id, stk_size, pext, opt);
if (err == OS_NO_ERR) {
if (OSRunning == TRUE) { /* Find HPT if multitasking has started */
OS_Sched();
}
} else {
OS_ENTER_CRITICAL();
OSTCBPrioTbl[prio] = (OS_TCB *)0; /* Make this priority avail. to others */
OS_EXIT_CRITICAL();
}
return (err);
}
OS_EXIT_CRITICAL();
return (OS_PRIO_EXIST);
}
#endif
/*$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_NOT_EXIST if the task is assigned to a Mutex PIP.
* 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 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;
cpu_sr = 0; /* Prevent compiler warning */
#endif
if (OSIntNesting > 0) { /* See if trying to delete from ISR */
return (OS_TASK_DEL_ISR);
}
#if OS_ARG_CHK_EN > 0
if (prio == OS_IDLE_PRIO) { /* Not allowed to delete idle task */
return (OS_TASK_DEL_IDLE);
}
if (prio >= OS_LOWEST_PRIO) { /* Task priority valid ? */
if (prio != OS_PRIO_SELF) {
return (OS_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_TASK_DEL_ERR);
}
if (ptcb == (OS_TCB *)1) { /* Must not be assigned to Mutex */
OS_EXIT_CRITICAL();
return (OS_TASK_NOT_EXIST);
}
y = ptcb->OSTCBY;
OSRdyTbl[y] &= ~ptcb->OSTCBBitX;
if (OSRdyTbl[y] == 0x00) { /* 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->OSTCBPendTO = FALSE;
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();
OS_Sched(); /* Find new highest priority task */
return (OS_NO_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 *p_arg)
* {
* .
* .
* 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_ERR if the task is assigned to a Mutex.
* 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.
*********************************************************************************************************
*/
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