ucos实时操作系统学习笔记——内核结构和任务创建

typedef struct os_pcb{
OS_STK *OSTCBStkPtr; /* Pointer to current top of stack */ struct os_tcb *OSTCBNext; /* Pointer to next TCB in the TCB list */
struct os_tcb *OSTCBPrev; /* Pointer to previous TCB in the TCB list */ INT32U OSTCBDly; /* Nbr ticks to delay task or, timeout waiting for event */
INT8U OSTCBStat; /* Task status */
INT8U OSTCBStatPend; /* Task PEND status */
INT8U OSTCBPrio; /* Task priority (0 == highest) */ INT8U OSTCBX; /* Bit position in group corresponding to task priority */
INT8U OSTCBY; /* Index into ready table corresponding to task priority */
OS_PRIO OSTCBBitX; /* Bit mask to access bit position in ready table */
OS_PRIO OSTCBBitY; /* Bit mask to access bit position in ready group */
}OS_TCB;

#if OS_LOWEST_PRIO <= 63u /* Pre-compute X, Y */
ptcb->OSTCBY = (INT8U)(prio >> 3u);
ptcb->OSTCBX = (INT8U)(prio & 0x07u);
#else /* Pre-compute X, Y */
ptcb->OSTCBY = (INT8U)((INT8U)(prio >> 4u) & 0xFFu);
ptcb->OSTCBX = (INT8U) (prio & 0x0Fu);
#endif
/* Pre-compute BitX and BitY */
ptcb->OSTCBBitY = (OS_PRIO)(1uL << ptcb->OSTCBY);
ptcb->OSTCBBitX = (OS_PRIO)(1uL << ptcb->OSTCBX);

static void OS_SchedNew (void)
{
#if OS_LOWEST_PRIO <= 63 /* See if we support up to 64 tasks */
INT8U y; y = OSUnMapTbl[OSRdyGrp];
OSPrioHighRdy = (INT8U)((y << ) + OSUnMapTbl[OSRdyTbl[y]]);
#else /* We support up to 256 tasks */
INT8U y;
INT16U *ptbl; if ((OSRdyGrp & 0xFF) != ) {
y = OSUnMapTbl[OSRdyGrp & 0xFF];
} else {
y = OSUnMapTbl[(OSRdyGrp >> ) & 0xFF] + ;
}
ptbl = &OSRdyTbl[y];
if ((*ptbl & 0xFF) != ) {
OSPrioHighRdy = (INT8U)((y << ) + OSUnMapTbl[(*ptbl & 0xFF)]);
} else {
OSPrioHighRdy = (INT8U)((y << ) + OSUnMapTbl[(*ptbl >> ) & 0xFF] + );
}
#endif
}

OS_EXT OS_TCB *OSTCBCur; /* Pointer to currently running TCB */
OS_EXT OS_TCB *OSTCBFreeList; /* Pointer to list of free TCBs */
OS_EXT OS_TCB *OSTCBHighRdy; /* Pointer to highest priority TCB R-to-R */
OS_EXT OS_TCB *OSTCBList; /* Pointer to doubly linked list of TCBs */
OS_EXT OS_TCB *OSTCBPrioTbl[OS_LOWEST_PRIO + ];/* Table of pointers to created TCBs */
OS_EXT OS_TCB OSTCBTbl[OS_MAX_TASKS + OS_N_SYS_TASKS]; /* Table of TCBs

INT8U OSTaskCreate (void (*task)(void *p_arg),
void *p_arg,
OS_STK *ptos,
INT8U prio)
{
OS_STK *psp;
INT8U err;
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 *)) { /* 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 *), 0u, 0u, (void *), 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 *);/* Make this priority available to others */
OS_EXIT_CRITICAL();
}
return (err);
}
OS_EXIT_CRITICAL();
return (OS_ERR_PRIO_EXIST);
}