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event的API的使用例程使用如下：首先初始化一个eventstatic EVENT_CB_S  example_event;uwRet = LOS_EventInit(&example_event);然后读这个event    uwEvent = LOS_EventRead(&example_event, event_wait, LOS_WAITMODE_AND, 100);    if(uwEvent == event_wait)    {        dprintf("Example_Event,read event :0x%x\n",uwEvent);        uwRet = LOS_InspectStatusSetByID(LOS_INSPECT_EVENT, LOS_INSPECT_STU_SUCCESS);        if (LOS_OK != uwRet)        {            dprintf("Set Inspect Status Err\n");        }    }    else    {        dprintf("Example_Event,read event timeout\n");        uwRet = LOS_InspectStatusSetByID(LOS_INSPECT_EVENT, LOS_INSPECT_STU_ERROR);        if (LOS_OK != uwRet)        {            dprintf("Set Inspect Status Err\n");        }    }最后写这个event    /* write event */    dprintf("Example_TaskEntry_Event write event .\n");    uwRet = LOS_EventWrite(&example_event, event_wait);    if(uwRet != LOS_OK)    {        dprintf("event write failed .\n");        return LOS_NOK;    }我们首先看看event的初始化LITE_OS_SEC_TEXT_INIT UINT32 LOS_EventInit(PEVENT_CB_S pstEventCB){#如果event id 为null，则返回，本例中event id是静态定义的    if (pstEventCB == NULL)    {        return LOS_ERRNO_EVENT_PTR_NULL;    }#将eventId 赋值为零    pstEventCB->uwEventID = 0;#每个event 有个list，这里将list置空    LOS_ListInit(&pstEventCB->stEventList);    return LOS_OK;}可以看到list将next和prev都指向了自己LITE_OS_SEC_ALW_INLINE STATIC_INLINE VOID LOS_ListInit(LOS_DL_LIST *pstList){    pstList->pstNext = pstList;    pstList->pstPrev = pstList;}下来我们看看event的read函数LITE_OS_SEC_TEXT UINT32 LOS_EventRead(PEVENT_CB_S pstEventCB, UINT32 uwEventMask, UINT32 uwMode, UINT32 uwTimeOut){    UINT32      uwRet = 0;    UINTPTR     uvIntSave;    LOS_TASK_CB *pstRunTsk;#保存中断    uvIntSave = LOS_IntLock();#这里的poll其实就是判断pstEventCB->uwEventID 和 uwEventMask, 以及uwMode直接的关系，并没有任何poll的动作    uwRet = LOS_EventPoll(&(pstEventCB->uwEventID), uwEventMask, uwMode);    if (uwRet == 0)    {                pstRunTsk = g_stLosTask.pstRunTask;        pstRunTsk->uwEventMask = uwEventMask;        pstRunTsk->uwEventMode = uwMode;#将当前task加到event的srEventList中，这里的uwTimeOut 如果不等于forever的话，还会建立一个timer在uwTimeOut到期后#唤醒这个task        osTaskWait(&pstEventCB->stEventList, OS_TASK_STATUS_PEND, uwTimeOut);#恢复中断        (VOID)LOS_IntRestore(uvIntSave);#当前task让出cpu        LOS_Schedule();#当再次执行task时判断这个task是否在timeout后才被唤醒的        if (pstRunTsk->usTaskStatus & OS_TASK_STATUS_TIMEOUT)        {            uvIntSave = LOS_IntLock();            pstRunTsk->usTaskStatus &= (~OS_TASK_STATUS_TIMEOUT);            (VOID)LOS_IntRestore(uvIntSave);            return LOS_ERRNO_EVENT_READ_TIMEOUT;        }        uvIntSave = LOS_IntLock();#如果不是timeout唤醒的，说明已经调用过event write，才被唤醒的，说明>uwEventID已经被更新了#再次判断这三者>uwEventID,uwEventMask,uwMode的关系后退出。        uwRet = LOS_EventPoll(&pstEventCB->uwEventID,uwEventMask,uwMode);        (VOID)LOS_IntRestore(uvIntSave);    }    else    {        (VOID)LOS_IntRestore(uvIntSave);    }    return uwRet;}最后再在看看event write函数LITE_OS_SEC_TEXT UINT32 LOS_EventWrite(PEVENT_CB_S pstEventCB, UINT32 uwEvents){    LOS_TASK_CB *pstResumedTask;    LOS_TASK_CB *pstNextTask = (LOS_TASK_CB *)NULL;    UINTPTR     uvIntSave;    UINT8       ucExitFlag = 0;    uvIntSave = LOS_IntLock();    pstEventCB->uwEventID |= uwEvents;#首先检测event的list是否为null，因为前面已经调用过event read函数了，所以这里肯定不为null    if (!LOS_ListEmpty(&pstEventCB->stEventList))    {        for (pstResumedTask = LOS_DL_LIST_ENTRY((&pstEventCB->stEventList)->pstNext, LOS_TASK_CB, stPendList);/*lint !e413*/            &pstResumedTask->stPendList != (&pstEventCB->stEventList);)        {#找到event list中第一个需要wakeup的task            pstNextTask = LOS_DL_LIST_ENTRY(pstResumedTask->stPendList.pstNext, LOS_TASK_CB, stPendList); /*lint !e413*/            if (((pstResumedTask->uwEventMode & LOS_WAITMODE_OR) && (pstResumedTask->uwEventMask & uwEvents) != 0) ||                ((pstResumedTask->uwEventMode & LOS_WAITMODE_AND) && (pstResumedTask->uwEventMask & pstEventCB->uwEventID) == pstResumedTask->uwEventMask))            {#设置flags，后面用于调度                ucExitFlag = 1;#wakeup这个task                osTaskWake(pstResumedTask, OS_TASK_STATUS_PEND);            }            pstResumedTask = pstNextTask;        }        if (ucExitFlag == 1)        {            (VOID)LOS_IntRestore(uvIntSave);#由于flag被置为1，说明有task 要被唤醒，开始调度            LOS_Schedule();            return LOS_OK;        }    }    (VOID)LOS_IntRestore(uvIntSave);    return LOS_OK;}

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