Chapter 3.2 - 用户任务管理
Created by : Mr Dk.
2019 / 11 / 18 22:54
Nanjing, Jiangsu, China
3.2.1 任务栈管理
三种堆栈：
- CPU 硬件堆栈 (系统栈或硬件栈)：保存中断或函数调用返回的 PC 以及其它 CPU 寄存器值
- 可重入函数的仿真堆栈
- 任务堆栈 (任务栈或用户栈)
任务栈可以静态或动态分配。任务栈的初始化仅为任务的第一次运行做准备，除了 PC 外，其余寄存器的值没有任何意义。
3.2.2 建立任务 - OSTaskCreate() 函数
将任务的 代码地址 和 参数 传递给内核：
- 判断优先级的有效性，是否被占用
- 分配并初始化任务的 TCB
- 该函数可以在多任务启动前或启动后调用
- 如果在多任务启动后调用
- 还需要判断一下是否高于当前程序的优先级
- 如果高于当前优先级，则发生任务切换，挂起当前任务
/*
*********************************************************************************************************
* CREATE A TASK
*
* Description: This function is used to have uC/OS-II manage the execution of a task. Tasks can either
* be created prior to the start of multitasking or by a running task. A task cannot be
* created by an ISR.
*
* Arguments : task is a pointer to the task's code
*
* p_arg is a pointer to an optional data area which can be used to pass parameters to
* the task when the task first executes. Where the task is concerned it thinks
* it was invoked and passed the argument 'p_arg' as follows:
*
* void Task (void *p_arg)
* {
* for (;;) {
* Task code;
* }
* }
*
* ptos is a pointer to the task's top 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). 'pstk' will thus point to the highest (valid) memory
* location of the stack. If OS_STK_GROWTH is set to 0, 'pstk' will point to the
* lowest memory location of the stack and the stack will grow with increasing
* memory locations.
*
* prio is the task's priority. A unique priority MUST be assigned to each task and the
* lower the number, the higher the priority.
*
* 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.
*********************************************************************************************************
*/
#if OS_TASK_CREATE_EN > 0u
INT8U OSTaskCreate (void (*task)(void *p_arg),
void *p_arg,
OS_STK *ptos,
INT8U prio)
{
OS_STK *psp;
INT8U err;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508
if (OSSafetyCriticalStartFlag == OS_TRUE) {
OS_SAFETY_CRITICAL_EXCEPTION();
}
#endif
#if OS_ARG_CHK_EN > 0u
if (prio > OS_LOWEST_PRIO) { /* Make sure priority is within allowable range */
return (OS_ERR_PRIO_INVALID);
}
#endif
OS_ENTER_CRITICAL();
if (OSIntNesting > 0u) { /* 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_RESERVED;/* Reserve the priority to prevent others from doing ... */
/* ... the same thing until task is created. */
OS_EXIT_CRITICAL();
psp = OSTaskStkInit(task, p_arg, ptos, 0u); /* Initialize the task's stack */
err = OS_TCBInit(prio, psp, (OS_STK *)0, 0u, 0u, (void *)0, 0u);
if (err == OS_ERR_NONE) {
if (OSRunning == OS_TRUE) { /* Find highest priority task if multitasking has started */
OS_Sched();
}
} else {
OS_ENTER_CRITICAL();
OSTCBPrioTbl[prio] = (OS_TCB *)0;/* Make this priority available to others */
OS_EXIT_CRITICAL();
}
return (err);
}
OS_EXIT_CRITICAL();
return (OS_ERR_PRIO_EXIST);
}
#endif
3.2.3 建立任务 - OSTaskCreateExt() 函数
前一个函数的扩展版本，总体上逻辑类似：
/*
*********************************************************************************************************
* CREATE A TASK (Extended Version)
*
* Description: This function is used to have uC/OS-II manage the execution of a task. Tasks can either
* be created prior to the start of multitasking or by a running task. A task cannot be
* created by an ISR. This function is similar to OSTaskCreate() except that it allows
* additional information about a task to be specified.
*
* Arguments : task is a pointer to the task's code
*
* p_arg is a pointer to an optional data area which can be used to pass parameters to
* the task when the task first executes. Where the task is concerned it thinks
* it was invoked and passed the argument 'p_arg' as follows:
*
* void Task (void *p_arg)
* {
* for (;;) {
* Task code;
* }
* }
*
* ptos is a pointer to the task's top 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). 'ptos' will thus point to the highest (valid) memory
* location of the stack. If OS_STK_GROWTH is set to 0, 'ptos' will point to the
* lowest memory location of the stack and the stack will grow with increasing
* memory locations. 'ptos' 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. 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 > 0u
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 == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508
if (OSSafetyCriticalStartFlag == OS_TRUE) {
OS_SAFETY_CRITICAL_EXCEPTION();
}
#endif
#if OS_ARG_CHK_EN > 0u
if (prio > OS_LOWEST_PRIO) { /* Make sure priority is within allowable range */
return (OS_ERR_PRIO_INVALID);
}
#endif
OS_ENTER_CRITICAL();
if (OSIntNesting > 0u) { /* 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_RESERVED;/* Reserve the priority to prevent others from doing ... */
/* ... the same thing until task is created. */
OS_EXIT_CRITICAL();
#if (OS_TASK_STAT_STK_CHK_EN > 0u)
OS_TaskStkClr(pbos, stk_size, opt); /* Clear the task stack (if needed) */
#endif
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
3.2.4 优先级变更 - OSTaskChangePrio() 函数
调该函数可以动态改变任务的优先级，调用者只能是任务。实现：
- 根据原任务处于就绪态还是等待态，在就绪表或等待表中用新优先级替换原优先级
- 修改 TCB
- 优先级变更后，会调用调度函数，可能会发生一次任务切换
新优先级必须是没有用过的。
/*
*********************************************************************************************************
* CHANGE PRIORITY OF A TASK
*
* Description: This function allows you to change the priority of a task dynamically. Note that the new
* priority MUST be available.
*
* Arguments : oldp is the old priority
*
* newp is the new priority
*
* Returns : OS_ERR_NONE is the call was successful
* OS_ERR_PRIO_INVALID if the priority you specify is higher that the maximum allowed
* (i.e. >= OS_LOWEST_PRIO)
* OS_ERR_PRIO_EXIST if the new priority already exist.
* OS_ERR_PRIO there is no task with the specified OLD priority (i.e. the OLD task does
* not exist.
* OS_ERR_TASK_NOT_EXIST if the task is assigned to a Mutex PIP.
*********************************************************************************************************
*/
#if OS_TASK_CHANGE_PRIO_EN > 0u
INT8U OSTaskChangePrio (INT8U oldprio,
INT8U newprio)
{
#if (OS_EVENT_EN)
OS_EVENT *pevent;
#if (OS_EVENT_MULTI_EN > 0u)
OS_EVENT **pevents;
#endif
#endif
OS_TCB *ptcb;
INT8U y_new;
INT8U x_new;
INT8U y_old;
OS_PRIO bity_new;
OS_PRIO bitx_new;
OS_PRIO bity_old;
OS_PRIO bitx_old;
#if OS_CRITICAL_METHOD == 3u
OS_CPU_SR cpu_sr = 0u; /* Storage for CPU status register */
#endif
/*$PAGE*/
#if OS_ARG_CHK_EN > 0u
if (oldprio >= OS_LOWEST_PRIO) {
if (oldprio != OS_PRIO_SELF) {
return (OS_ERR_PRIO_INVALID);
}
}
if (newprio >= OS_LOWEST_PRIO) {
return (OS_ERR_PRIO_INVALID);
}
#endif
OS_ENTER_CRITICAL();
if (OSTCBPrioTbl[newprio] != (OS_TCB *)0) { /* New priority must not already exist */
OS_EXIT_CRITICAL();
return (OS_ERR_PRIO_EXIST);
}
if (oldprio == OS_PRIO_SELF) { /* See if changing self */
oldprio = OSTCBCur->OSTCBPrio; /* Yes, get priority */
}
ptcb = OSTCBPrioTbl[oldprio];
if (ptcb == (OS_TCB *)0) { /* Does task to change exist? */
OS_EXIT_CRITICAL(); /* No, can't change its priority! */
return (OS_ERR_PRIO);
}
if (ptcb == OS_TCB_RESERVED) { /* Is task assigned to Mutex */
OS_EXIT_CRITICAL(); /* No, can't change its priority! */
return (OS_ERR_TASK_NOT_EXIST);
}
#if OS_LOWEST_PRIO <= 63u
y_new = (INT8U)(newprio >> 3u); /* Yes, compute new TCB fields */
x_new = (INT8U)(newprio & 0x07u);
#else
y_new = (INT8U)((INT8U)(newprio >> 4u) & 0x0Fu);
x_new = (INT8U)(newprio & 0x0Fu);
#endif
bity_new = (OS_PRIO)(1uL << y_new);
bitx_new = (OS_PRIO)(1uL << x_new);
OSTCBPrioTbl[oldprio] = (OS_TCB *)0; /* Remove TCB from old priority */
OSTCBPrioTbl[newprio] = ptcb; /* Place pointer to TCB @ new priority */
y_old = ptcb->OSTCBY;
bity_old = ptcb->OSTCBBitY;
bitx_old = ptcb->OSTCBBitX;
if ((OSRdyTbl[y_old] & bitx_old) != 0u) { /* If task is ready make it not */
OSRdyTbl[y_old] &= (OS_PRIO)~bitx_old;
if (OSRdyTbl[y_old] == 0u) {
OSRdyGrp &= (OS_PRIO)~bity_old;
}
OSRdyGrp |= bity_new; /* Make new priority ready to run */
OSRdyTbl[y_new] |= bitx_new;
}
#if (OS_EVENT_EN)
pevent = ptcb->OSTCBEventPtr;
if (pevent != (OS_EVENT *)0) {
pevent->OSEventTbl[y_old] &= (OS_PRIO)~bitx_old; /* Remove old task prio from wait list */
if (pevent->OSEventTbl[y_old] == 0u) {
pevent->OSEventGrp &= (OS_PRIO)~bity_old;
}
pevent->OSEventGrp |= bity_new; /* Add new task prio to wait list */
pevent->OSEventTbl[y_new] |= bitx_new;
}
#if (OS_EVENT_MULTI_EN > 0u)
if (ptcb->OSTCBEventMultiPtr != (OS_EVENT **)0) {
pevents = ptcb->OSTCBEventMultiPtr;
pevent = *pevents;
while (pevent != (OS_EVENT *)0) {
pevent->OSEventTbl[y_old] &= (OS_PRIO)~bitx_old; /* Remove old task prio from wait lists */
if (pevent->OSEventTbl[y_old] == 0u) {
pevent->OSEventGrp &= (OS_PRIO)~bity_old;
}
pevent->OSEventGrp |= bity_new; /* Add new task prio to wait lists */
pevent->OSEventTbl[y_new] |= bitx_new;
pevents++;
pevent = *pevents;
}
}
#endif
#endif
ptcb->OSTCBPrio = newprio; /* Set new task priority */
ptcb->OSTCBY = y_new;
ptcb->OSTCBX = x_new;
ptcb->OSTCBBitY = bity_new;
ptcb->OSTCBBitX = bitx_new;
OS_EXIT_CRITICAL();
if (OSRunning == OS_TRUE) {
OS_Sched(); /* Find new highest priority task */
}
return (OS_ERR_NONE);
}
#endif
3.2.5 删除任务 - OSTaskDel() 函数
不删除任务代码
- 使任务返回并处于休眠
- 任务的代码不再被 OS 管理，除非重新启动
调用后，下一个就绪的最高优先级任务开始运行，发生一次任务切换。可以删除自己，但是在删除占用系统资源的任务时要小心。
具体实现：
- 将该任务从内核中的所有地方移走
- 如果就绪，就从就绪表中移走
- 如果在等待，就从等待列表中移走
- 将 TCB 设置后，从链表中删除
- 重新调度
/*
*********************************************************************************************************
* 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.
*********************************************************************************************************
*/
#if OS_TASK_DEL_EN > 0u
INT8U OSTaskDel (INT8U prio)
{
#if (OS_FLAG_EN > 0u) && (OS_MAX_FLAGS > 0u)
OS_FLAG_NODE *pnode;
#endif
OS_TCB *ptcb;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
if (OSIntNesting > 0u) { /* 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 > 0u
if (prio >= OS_LOWEST_PRIO) { /* Task priority valid ? */
if (prio != OS_PRIO_SELF) {
return (OS_ERR_PRIO_INVALID);
}
}
#endif
/*$PAGE*/
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_RESERVED) { /* Must not be assigned to Mutex */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_DEL);
}
OSRdyTbl[ptcb->OSTCBY] &= (OS_PRIO)~ptcb->OSTCBBitX;
if (OSRdyTbl[ptcb->OSTCBY] == 0u) { /* Make task not ready */
OSRdyGrp &= (OS_PRIO)~ptcb->OSTCBBitY;
}
#if (OS_EVENT_EN)
if (ptcb->OSTCBEventPtr != (OS_EVENT *)0) {
OS_EventTaskRemove(ptcb, ptcb->OSTCBEventPtr); /* Remove this task from any event wait list */
}
#if (OS_EVENT_MULTI_EN > 0u)
if (ptcb->OSTCBEventMultiPtr != (OS_EVENT **)0) { /* Remove this task from any events' wait lists*/
OS_EventTaskRemoveMulti(ptcb, ptcb->OSTCBEventMultiPtr);
}
#endif
#endif
#if (OS_FLAG_EN > 0u) && (OS_MAX_FLAGS > 0u)
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 = 0u; /* 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 > 0u) { /* 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_EN > 0u
ptcb->OSTCBTaskName = (INT8U *)(void *)"?";
#endif
OS_EXIT_CRITICAL();
if (OSRunning == OS_TRUE) {
OS_Sched(); /* Find new highest priority task */
}
return (OS_ERR_NONE);
}
#endif
3.2.6 请求删除任务 - OSTaskDelReq() 函数
系统资源可能因为被某个被删除任务持有而丢失。该函数可以使任务在使用完资源后，先释放，再被删除。具体实现：
- 确保要删除的优先级有效
- 若任务存在，则在 TCB 中设置标志
/*
*********************************************************************************************************
* 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.
* OS_ERR_TASK_DEL_IDLE if you requested 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_REQ if a task (possibly another task) requested that the running task be
* deleted.
*********************************************************************************************************
*/
/*$PAGE*/
#if OS_TASK_DEL_EN > 0u
INT8U OSTaskDelReq (INT8U prio)
{
INT8U stat;
OS_TCB *ptcb;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
if (prio == OS_TASK_IDLE_PRIO) { /* Not allowed to delete idle task */
return (OS_ERR_TASK_DEL_IDLE);
}
#if OS_ARG_CHK_EN > 0u
if (prio >= OS_LOWEST_PRIO) { /* Task priority valid ? */
if (prio != OS_PRIO_SELF) {
return (OS_ERR_PRIO_INVALID);
}
}
#endif
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);
}
OS_ENTER_CRITICAL();
ptcb = OSTCBPrioTbl[prio];
if (ptcb == (OS_TCB *)0) { /* Task to delete must exist */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_EXIST); /* Task must already be deleted */
}
if (ptcb == OS_TCB_RESERVED) { /* Must NOT be assigned to a Mutex */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_DEL);
}
ptcb->OSTCBDelReq = OS_ERR_TASK_DEL_REQ; /* Set flag indicating task to be DEL. */
OS_EXIT_CRITICAL();
return (OS_ERR_NONE);
}
#endif
3.2.7 堆栈检验 - OSTaskStkChk() 函数
检查任务所需任务栈的空间大小。
3.2.8 任务挂起 - OSTaskSuspend() 函数
无条件挂起一个任务：
- 必须和任务恢复函数
OSTaskResume()成对使用 - 任务可以挂起自己，或其它任务
- 本任务被挂起后，只能由其它任务恢复
原理：
- 检查任务是否就绪，如果就绪，则移出就绪表
- 在 TCB 中设置标志，表示任务被挂起
- 重新调度
/*
*********************************************************************************************************
* SUSPEND A TASK
*
* Description: This function is called to suspend a task. The task can be the calling task if the
* priority passed to OSTaskSuspend() is the priority of the calling task or OS_PRIO_SELF.
*
* Arguments : prio is the priority of the task to suspend. If you specify OS_PRIO_SELF, the
* calling task will suspend itself and rescheduling will occur.
*
* Returns : OS_ERR_NONE if the requested task is suspended
* OS_ERR_TASK_SUSPEND_IDLE if you attempted to suspend the idle task which is not allowed.
* 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_SUSPEND_PRIO if the task to suspend does not exist
* OS_ERR_TASK_NOT_EXITS if the task is assigned to a Mutex PIP
*
* Note : You should use this function with great care. If you suspend a task that is waiting for
* an event (i.e. a message, a semaphore, a queue ...) you will prevent this task from
* running when the event arrives.
*********************************************************************************************************
*/
#if OS_TASK_SUSPEND_EN > 0u
INT8U OSTaskSuspend (INT8U prio)
{
BOOLEAN self;
OS_TCB *ptcb;
INT8U y;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#if OS_ARG_CHK_EN > 0u
if (prio == OS_TASK_IDLE_PRIO) { /* Not allowed to suspend idle task */
return (OS_ERR_TASK_SUSPEND_IDLE);
}
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 suspend SELF */
prio = OSTCBCur->OSTCBPrio;
self = OS_TRUE;
} else if (prio == OSTCBCur->OSTCBPrio) { /* See if suspending self */
self = OS_TRUE;
} else {
self = OS_FALSE; /* No suspending another task */
}
ptcb = OSTCBPrioTbl[prio];
if (ptcb == (OS_TCB *)0) { /* Task to suspend must exist */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_SUSPEND_PRIO);
}
if (ptcb == OS_TCB_RESERVED) { /* See if assigned to Mutex */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_EXIST);
}
y = ptcb->OSTCBY;
OSRdyTbl[y] &= (OS_PRIO)~ptcb->OSTCBBitX; /* Make task not ready */
if (OSRdyTbl[y] == 0u) {
OSRdyGrp &= (OS_PRIO)~ptcb->OSTCBBitY;
}
ptcb->OSTCBStat |= OS_STAT_SUSPEND; /* Status of task is 'SUSPENDED' */
OS_EXIT_CRITICAL();
if (self == OS_TRUE) { /* Context switch only if SELF */
OS_Sched(); /* Find new highest priority task */
}
return (OS_ERR_NONE);
}
#endif
3.2.9 任务恢复 - OSTaskResume() 函数
唯一能唤醒被挂起任务的函数。原理：
- 清除 TCB 中的挂起标志
- 若任务就绪，则将任务加入就绪表
- 重新调度
/*
*********************************************************************************************************
* 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_ERR_NONE if the requested task is resumed
* OS_ERR_PRIO_INVALID if the priority you specify is higher that the maximum allowed
* (i.e. >= OS_LOWEST_PRIO)
* OS_ERR_TASK_RESUME_PRIO if the task to resume does not exist
* OS_ERR_TASK_NOT_EXIST if the task is assigned to a Mutex PIP
* OS_ERR_TASK_NOT_SUSPENDED if the task to resume has not been suspended
*********************************************************************************************************
*/
#if OS_TASK_SUSPEND_EN > 0u
INT8U OSTaskResume (INT8U prio)
{
OS_TCB *ptcb;
#if OS_CRITICAL_METHOD == 3u /* Storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#if OS_ARG_CHK_EN > 0u
if (prio >= OS_LOWEST_PRIO) { /* Make sure task priority is valid */
return (OS_ERR_PRIO_INVALID);
}
#endif
OS_ENTER_CRITICAL();
ptcb = OSTCBPrioTbl[prio];
if (ptcb == (OS_TCB *)0) { /* Task to suspend must exist */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_RESUME_PRIO);
}
if (ptcb == OS_TCB_RESERVED) { /* See if assigned to Mutex */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_EXIST);
}
if ((ptcb->OSTCBStat & OS_STAT_SUSPEND) != OS_STAT_RDY) { /* Task must be suspended */
ptcb->OSTCBStat &= (INT8U)~(INT8U)OS_STAT_SUSPEND; /* Remove suspension */
if (ptcb->OSTCBStat == OS_STAT_RDY) { /* See if task is now ready */
if (ptcb->OSTCBDly == 0u) {
OSRdyGrp |= ptcb->OSTCBBitY; /* Yes, Make task ready to run */
OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
OS_EXIT_CRITICAL();
if (OSRunning == OS_TRUE) {
OS_Sched(); /* Find new highest priority task */
}
} else {
OS_EXIT_CRITICAL();
}
} else { /* Must be pending on event */
OS_EXIT_CRITICAL();
}
return (OS_ERR_NONE);
}
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_SUSPENDED);
}
#endif
3.2.10 任务信息的获取 - OSTaskQuery() 函数
获取自身或其它任务的信息，其实是返回任务 TCB 的一个拷贝。所以任务需要分配一个 OS_TCB 类型的空间
/*
*********************************************************************************************************
* QUERY A TASK
*
* Description: This function is called to obtain a copy of the desired task's TCB.
*
* Arguments : prio is the priority of the task to obtain information from.
*
* p_task_data is a pointer to where the desired task's OS_TCB will be stored.
*
* Returns : OS_ERR_NONE if the requested task is suspended
* 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_PRIO if the desired task has not been created
* OS_ERR_TASK_NOT_EXIST if the task is assigned to a Mutex PIP
* OS_ERR_PDATA_NULL if 'p_task_data' is a NULL pointer
*********************************************************************************************************
*/
#if OS_TASK_QUERY_EN > 0u
INT8U OSTaskQuery (INT8U prio,
OS_TCB *p_task_data)
{
OS_TCB *ptcb;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#if OS_ARG_CHK_EN > 0u
if (prio > OS_LOWEST_PRIO) { /* Task priority valid ? */
if (prio != OS_PRIO_SELF) {
return (OS_ERR_PRIO_INVALID);
}
}
if (p_task_data == (OS_TCB *)0) { /* Validate 'p_task_data' */
return (OS_ERR_PDATA_NULL);
}
#endif
OS_ENTER_CRITICAL();
if (prio == OS_PRIO_SELF) { /* See if suspend SELF */
prio = OSTCBCur->OSTCBPrio;
}
ptcb = OSTCBPrioTbl[prio];
if (ptcb == (OS_TCB *)0) { /* Task to query must exist */
OS_EXIT_CRITICAL();
return (OS_ERR_PRIO);
}
if (ptcb == OS_TCB_RESERVED) { /* Task to query must not be assigned to a Mutex */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_EXIST);
}
/* Copy TCB into user storage area */
OS_MemCopy((INT8U *)p_task_data, (INT8U *)ptcb, sizeof(OS_TCB));
OS_EXIT_CRITICAL();
return (OS_ERR_NONE);
}
#endif
Summary
从总体上来说，μC/OS-II 的逻辑比 Linux 简单多了。主要的差别在于没有那些复杂的内存管理机制，也没有复杂的调度算法。TCB 也比 Linux 简单很多。优美源自于简单吧 🥱