ucOS学习笔记(3)——ucOS的数据结构

ucOS的数据结构中最核心的一个数据结构就是任务控制块数据结构，其他的数据类型都是围绕该数据结构展开的，任务切换，代码调度也都是以该数据结构为基础来完成的。认清了该数据结构就了解了ucOS的运行机制。任务控制块数据结构如下：

typedef struct os_tcb {
    OS_STK          *OSTCBStkPtr;           /* Pointer to current top of stack                         */

#if OS_TASK_CREATE_EXT_EN > 0
    void            *OSTCBExtPtr;           /* Pointer to user definable data for TCB extension        */
    OS_STK          *OSTCBStkBottom;        /* Pointer to bottom of stack                              */
    INT32U           OSTCBStkSize;          /* Size of task stack (in number of stack elements)        */
    INT16U           OSTCBOpt;              /* Task options as passed by OSTaskCreateExt()             */
    INT16U           OSTCBId;               /* Task ID (0..65535)                                      */
#endif

    struct os_tcb   *OSTCBNext;             /* Pointer to next     TCB in the TCB list                 */
    struct os_tcb   *OSTCBPrev;             /* Pointer to previous TCB in the TCB list                 */

#if (OS_EVENT_EN) || (OS_FLAG_EN > 0)
    OS_EVENT        *OSTCBEventPtr;         /* Pointer to          event control block                 */
#endif

#if (OS_EVENT_EN) && (OS_EVENT_MULTI_EN > 0)
    OS_EVENT       **OSTCBEventMultiPtr;    /* Pointer to multiple event control blocks                */
#endif

#if ((OS_Q_EN > 0) && (OS_MAX_QS > 0)) || (OS_MBOX_EN > 0)
    void            *OSTCBMsg;              /* Message received from OSMboxPost() or OSQPost()         */
#endif

#if (OS_FLAG_EN > 0) && (OS_MAX_FLAGS > 0)
#if OS_TASK_DEL_EN > 0
    OS_FLAG_NODE    *OSTCBFlagNode;         /* Pointer to event flag node                              */
#endif
    OS_FLAGS         OSTCBFlagsRdy;         /* Event flags that made task ready to run                 */
#endif

    INT16U           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   */
#if OS_LOWEST_PRIO <= 63
    INT8U            OSTCBBitX;             /* Bit mask to access bit position in ready table          */
    INT8U            OSTCBBitY;             /* Bit mask to access bit position in ready group          */
#else
    INT16U           OSTCBBitX;             /* Bit mask to access bit position in ready table          */
    INT16U           OSTCBBitY;             /* Bit mask to access bit position in ready group          */
#endif

#if OS_TASK_DEL_EN > 0
    INT8U            OSTCBDelReq;           /* Indicates whether a task needs to delete itself         */
#endif

#if OS_TASK_PROFILE_EN > 0
    INT32U           OSTCBCtxSwCtr;         /* Number of time the task was switched in                 */
    INT32U           OSTCBCyclesTot;        /* Total number of clock cycles the task has been running  */
    INT32U           OSTCBCyclesStart;      /* Snapshot of cycle counter at start of task resumption   */
    OS_STK          *OSTCBStkBase;          /* Pointer to the beginning of the task stack              */
    INT32U           OSTCBStkUsed;          /* Number of bytes used from the stack                     */
#endif

#if OS_TASK_NAME_SIZE > 1
    INT8U            OSTCBTaskName[OS_TASK_NAME_SIZE];
#endif
} OS_TCB;
其中
OSTCBStkPtr--任务栈的指针，在任务中使用到的所有零时变量(包括任务切换时需要保存的上下文)都保存在OSTCBStkPtr指向的存储区域
OSTCBExtPtr--任务扩展数据信息指针，目前我理解这一部分主要用于保存任务名字的ASCII码
OSTCBStkBottom--任务栈底指针
OSTCBStkSize--任务栈的大小
OSTCBNext--任务控制块链表中的下一任务指针
OSTCBPrev--任务控制块链表中的上一任务指针
OSTCBEventPtr--任务等待时间指针，该数据结构本身是属于一个事件的，任务也只是属于事件的一个候选资源
OSTCBEventMultiPtr--互斥信号量指针
OSTCBMsg--邮箱指针