要使用 uC/OS 的任务必须先声明任务控制块和创建任务，调用 OSTaskCreate () 函数可以创建一个任务。OSTaskCreate () 函数的信息如下表所示。
OSTaskCreate () 函数的定义位于“os_task.c”:
void OSTaskCreate (OS_TCB *p_tcb, CPU_CHAR *p_name, OS_TASK_PTR p_task, void *p_arg, OS_PRIO prio, CPU_STK *p_stk_base, CPU_STK_SIZE stk_limit, CPU_STK_SIZE stk_size, OS_MSG_QTY q_size, OS_TICK time_quanta, void *p_ext, OS_OPT opt, OS_ERR *p_err) { CPU_STK_SIZE i; #if OS_CFG_TASK_REG_TBL_SIZE > 0u OS_REG_ID reg_nbr; #endif #if defined(OS_CFG_TLS_TBL_SIZE) && (OS_CFG_TLS_TBL_SIZE > 0u) OS_TLS_ID id; #endif CPU_STK *p_sp; CPU_STK *p_stk_limit; CPU_SR_ALLOC(); #ifdef OS_SAFETY_CRITICAL if (p_err == (OS_ERR *)0) { OS_SAFETY_CRITICAL_EXCEPTION(); return; } #endif #ifdef OS_SAFETY_CRITICAL_IEC61508 if (OSSafetyCriticalStartFlag == DEF_TRUE) { *p_err = OS_ERR_ILLEGAL_CREATE_RUN_TIME; return; } #endif #if OS_CFG_CALLED_FROM_ISR_CHK_EN > 0u if (OSIntNestingCtr > (OS_NESTING_CTR)0) { /* ---------- CANNOT CREATE A TASK FROM AN ISR ---------- */ *p_err = OS_ERR_TASK_CREATE_ISR; return; } #endif #if OS_CFG_ARG_CHK_EN > 0u /* ---------------- VALIDATE ARGUMENTS ------------------ */ if (p_tcb == (OS_TCB *)0) { /* User must supply a valid OS_TCB */ *p_err = OS_ERR_TCB_INVALID; return; } if (p_task == (OS_TASK_PTR)0) { /* User must supply a valid task */ *p_err = OS_ERR_TASK_INVALID; return; } if (p_stk_base == (CPU_STK *)0) { /* User must supply a valid stack base address */ *p_err = OS_ERR_STK_INVALID; return; } if (stk_size < OSCfg_StkSizeMin) { /* User must supply a valid minimum stack size */ *p_err = OS_ERR_STK_SIZE_INVALID; return; } if (stk_limit >= stk_size) { /* User must supply a valid stack limit */ *p_err = OS_ERR_STK_LIMIT_INVALID; return; } if (prio >= OS_CFG_PRIO_MAX) { /* Priority must be within 0 and OS_CFG_PRIO_MAX-1 */ *p_err = OS_ERR_PRIO_INVALID; return; } #endif #if OS_CFG_ISR_POST_DEFERRED_EN > 0u if (prio == (OS_PRIO)0) { if (p_tcb != &OSIntQTaskTCB) { *p_err = OS_ERR_PRIO_INVALID; /* Not allowed to use priority 0 */ return; } } #endif if (prio == (OS_CFG_PRIO_MAX - 1u)) { if (p_tcb != &OSIdleTaskTCB) { *p_err = OS_ERR_PRIO_INVALID; /* Not allowed to use same priority as idle task */ return; } } OS_TaskInitTCB(p_tcb); /* Initialize the TCB to default values */ *p_err = OS_ERR_NONE; /* --------------- CLEAR THE TASK'S STACK --------------- */ if ((opt & OS_OPT_TASK_STK_CHK) != (OS_OPT)0) { /* See if stack checking has been enabled */ if ((opt & OS_OPT_TASK_STK_CLR) != (OS_OPT)0) { /* See if stack needs to be cleared */ p_sp = p_stk_base; for (i = 0u; i < stk_size; i++) { /* Stack grows from HIGH to LOW memory */ *p_sp = (CPU_STK)0; /* Clear from bottom of stack and up! */ p_sp++; } } } /* ------- INITIALIZE THE STACK FRAME OF THE TASK ------- */ #if (CPU_CFG_STK_GROWTH == CPU_STK_GROWTH_HI_TO_LO) p_stk_limit = p_stk_base + stk_limit; #else p_stk_limit = p_stk_base + (stk_size - 1u) - stk_limit; #endif p_sp = OSTaskStkInit(p_task, p_arg, p_stk_base, p_stk_limit, stk_size, opt); /* -------------- INITIALIZE THE TCB FIELDS ------------- */ p_tcb->TaskEntryAddr = p_task; /* Save task entry point address */ p_tcb->TaskEntryArg = p_arg; /* Save task entry argument */ p_tcb->NamePtr = p_name; /* Save task name */ p_tcb->Prio = prio; /* Save the task's priority */ p_tcb->StkPtr = p_sp; /* Save the new top-of-stack pointer */ p_tcb->StkLimitPtr = p_stk_limit; /* Save the stack limit pointer */ p_tcb->TimeQuanta = time_quanta; /* Save the #ticks for time slice (0 means not sliced) */ #if OS_CFG_SCHED_ROUND_ROBIN_EN > 0u if (time_quanta == (OS_TICK)0) { p_tcb->TimeQuantaCtr = OSSchedRoundRobinDfltTimeQuanta; } else { p_tcb->TimeQuantaCtr = time_quanta; } #endif p_tcb->ExtPtr = p_ext; /* Save pointer to TCB extension */ p_tcb->StkBasePtr = p_stk_base; /* Save pointer to the base address of the stack */ p_tcb->StkSize = stk_size; /* Save the stack size (in number of CPU_STK elements) */ p_tcb->Opt = opt; /* Save task options */ #if OS_CFG_TASK_REG_TBL_SIZE > 0u for (reg_nbr = 0u; reg_nbr < OS_CFG_TASK_REG_TBL_SIZE; reg_nbr++) { p_tcb->RegTbl[reg_nbr] = (OS_REG)0; } #endif #if OS_CFG_TASK_Q_EN > 0u OS_MsgQInit(&p_tcb->MsgQ, /* Initialize the task's message queue */ q_size); #else (void)&q_size; #endif OSTaskCreateHook(p_tcb); /* Call user defined hook */ #if defined(OS_CFG_TLS_TBL_SIZE) && (OS_CFG_TLS_TBL_SIZE > 0u) for (id = 0u; id < OS_CFG_TLS_TBL_SIZE; id++) { p_tcb->TLS_Tbl[id] = (OS_TLS)0; } OS_TLS_TaskCreate(p_tcb); /* Call TLS hook */ #endif /* --------------- ADD TASK TO READY LIST --------------- */ OS_CRITICAL_ENTER(); OS_PrioInsert(p_tcb->Prio); OS_RdyListInsertTail(p_tcb); #if OS_CFG_DBG_EN > 0u OS_TaskDbgListAdd(p_tcb); #endif OSTaskQty++; /* Increment the #tasks counter */ if (OSRunning != OS_STATE_OS_RUNNING) { /* Return if multitasking has not started */ OS_CRITICAL_EXIT(); return; } OS_CRITICAL_EXIT_NO_SCHED(); OSSched(); }