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【HarmonyOS】鸿蒙内核源码分析(tick 时钟管理篇)

2020-10-14 14:47:10 1632 HarmonyOS

0 本帖最后由 l_xy 于 2020-10-18 17:26 编辑原文链接：https://my.oschina.net/u/3751245/blog/4574493 目录多久Tick一次？看代码在哪里设置tick的回调函数？ OsTaskScan() 除了tick 会触发调度，还有哪些情况会触发调度？时钟管理模块很简单，但却有内核最重要的代码段 OstickHandler()，这是干嘛的，可以理解为 JAVA的定时任务，但这是系统内核的定时器。因鸿蒙目前开放的是轻量级的内核 lite os (LOS)，所以tick的频率不会太高对应张大爷的故事：很简单就是场馆的那个大钟，每10分响一次，一次就是一个Tick(节拍) 多久Tick一次？看代码 /** * @ingroup los_config * Number of Ticks in one second / #ifndef LOSCFG_BASE_CORE_TICK_PER_SECOND #define LOSCFG_BASE_CORE_TICK_PER_SECOND 100 //kfy 默认每秒100次触发，当然这是可以改的 #endif 复制代码每秒100 tick ，即每秒100次调用时钟中断处理程序, 时间片单位为10ms 一次任务分配多少时间给进程执行呢？答案是 2个时间片，即 20ms 对应张大爷的故事：节目喊到后这次进来的总表演时间，10分钟一个时间片，共2片，表演20分钟。 /** * @ingroup los_config * Longest execution time of tasks with the same priorities / #ifndef LOSCFG_BASE_CORE_TIMESLICE_TIMEOUT #define LOSCFG_BASE_CORE_TIMESLICE_TIMEOUT 2 #endif /* * @ingroup los_process * Hold the time slice process / #define OS_PROCESS_SCHED_RR_INTERVAL LOSCFG_BASE_CORE_TIMESLICE_TIMEOUT 复制代码* 用完需要可以再分配，但一次就是只给2个时间片，怕你一直占着茅坑，后面还有人在等的.详细代码： OsSchedResched(VOID) VOID OsSchedResched(VOID) { LosTaskCB runTask = NULL; LosTaskCB newTask = NULL; LosProcessCB runProcess = NULL; LosProcessCB newProcess = NULL; LOS_ASSERT(LOS_SpinHeld(&g_taskSpin)); if (!OsPreemptableInSched()) { return; } runTask = OsCurrTaskGet(); newTask = OsGetTopTask(); /* always be able to get one task / LOS_ASSERT(newTask != NULL); if (runTask == newTask) { return; } runTask->taskStatus &= ~OS_TASK_STATUS_RUNNING; newTask->taskStatus \|= OS_TASK_STATUS_RUNNING; runProcess = OS_PCB_FROM_PID(runTask->processID); newProcess = OS_PCB_FROM_PID(newTask->processID); OsSchedSwitchProcess(runProcess, newProcess); #if (LOSCFG_KERNEL_SMP == YES) / mask new running task's owner processor / runTask->currCpu = OS_TASK_INVALID_CPUID; newTask->currCpu = ArchCurrCpuid(); #endif (VOID)OsTaskSwitchCheck(runTask, newTask); #if (LOSCFG_KERNEL_SCHED_STATISTICS == YES) OsSchedStatistics(runTask, newTask); #endif if ((newTask->timeSlice == 0) && (newTask->policy == LOS_SCHED_RR)) { newTask->timeSlice = LOSCFG_BASE_CORE_TIMESLICE_TIMEOUT; //只给两个时间片 } OsCurrTaskSet((VOID)newTask); if (OsProcessIsUserMode(newProcess)) { OsCurrUserTaskSet(newTask->userArea); } PRINT_TRACE("cpu%d run process name: (%s) pid: %d status: %x threadMap: %x task name: (%s) tid: %d status: %x ->n" " new process name: (%s) pid: %d status: %x threadMap: %x task name: (%s) tid: %d status: %x!n", ArchCurrCpuid(), runProcess->processName, runProcess->processID, runProcess->processStatus, runProcess->threadScheduleMap, runTask->taskName, runTask->taskID, runTask->taskStatus, newProcess->processName, newProcess->processID, newProcess->processStatus, newProcess->threadScheduleMap, newTask->taskName, newTask->taskID, newTask->taskStatus); /* do the task context switch / OsTaskSchedule(newTask, runTask); } 复制代码* 在哪里设置tick的回调函数？从main中可以看到tick 的初始化和中断服务程序的注册 // 由 main 函数调用，注册中断处理函数 OsTickEntry VOID HalClockInit(VOID) { UINT32 ret; ret = LOS_HwiCreate(PRVTIMER_INT_NUM, 0xa0, 0, OsTickEntry, NULL); if (ret != LOS_OK) { PRINT_ERR("%s, %d create tick irq failed, ret:0x%xn", __FUNCTION__, __LINE__, ret); } } 复制代码 OsTickHandler 是tick 的中断处理程序，其中完成了时间片的检查和任务的扫描。 /* * Description : Tick interruption handler / LITE_OS_SEC_TEXT VOID OsTickHandler(VOID) { UINT32 intSave; TICK_LOCK(intSave); g_tickCount[ArchCurrCpuid()]++; TICK_UNLOCK(intSave); #ifdef LOSCFG_KERNEL_VDSO OsUpdateVdsoTimeval(); #endif #ifdef LOSCFG_KERNEL_TICKLESS OsTickIrqFlagSet(OsTicklessFlagGet()); #endif #if (LOSCFG_BASE_CORE_TICK_HW_TIME == YES) HalClockIrqClear(); / diff from every platform / #endif OsTimesliceCheck(); OsTaskScan(); / task timeout scan / #if (LOSCFG_BASE_CORE_SWTMR == YES) OsSwtmrScan(); #endif } LITE_OS_SEC_TEXT VOID OsTimesliceCheck(VOID) { LosTaskCB runTask = NULL; LosProcessCB runProcess = OsCurrProcessGet(); if (runProcess->policy != LOS_SCHED_RR) { goto SCHED_TASK; } if (runProcess->timeSlice != 0) { runProcess->timeSlice--;//进程时间片减少一次 if (runProcess->timeSlice == 0) { LOS_Schedule();//进程时间片用完,发起调度 } } SCHED_TASK: runTask = OsCurrTaskGet(); if (runTask->policy != LOS_SCHED_RR) { return; } if (runTask->timeSlice != 0) { runTask->timeSlice--;//对应任务时间片也减少一次 if (runTask->timeSlice == 0) { LOS_Schedule(); } } } 复制代码* OsTaskScan() OsTaskScan()不断查task的状态，有任务就去执行，毫不夸张的可以说是进程有序执行的源动力之所在！ LITE_OS_SEC_TEXT VOID OsTaskScan(VOID) { SortLinkList sortList = NULL; LosTaskCB taskCB = NULL; BOOL needSchedule = FALSE; UINT16 tempStatus; LOS_DL_LIST listObject = NULL; SortLinkAttribute taskSortLink = NULL; taskSortLink = &OsPercpuGet()->taskSortLink; taskSortLink->cursor = (taskSortLink->cursor + 1) & OS_TSK_SORTLINK_MASK; listObject = taskSortLink->sortLink + taskSortLink->cursor; /* * When task is pended with timeout, the task block is on the timeout sortlink * (per cpu) and ipc(mutex,sem and etc.)'s block at the same time, it can be waken * up by either timeout or corresponding ipc it's waiting. * * Now synchronize sortlink preocedure is used, therefore the whole task scan needs * to be protected, preventing another core from doing sortlink deletion at same time. / LOS_SpinLock(&g_taskSpin); if (LOS_ListEmpty(listObject)) { LOS_SpinUnlock(&g_taskSpin); return; } sortList = LOS_DL_LIST_ENTRY(listObject->pstNext, SortLinkList, sortLinkNode); ROLLNUM_DEC(sortList->idxRollNum); while (ROLLNUM(sortList->idxRollNum) == 0) { LOS_ListDelete(&sortList->sortLinkNode); taskCB = LOS_DL_LIST_ENTRY(sortList, LosTaskCB, sortList); taskCB->taskStatus &= ~OS_TASK_STATUS_PEND_TIME; tempStatus = taskCB->taskStatus; if (tempStatus & OS_TASK_STATUS_PEND) { taskCB->taskStatus &= ~OS_TASK_STATUS_PEND; #if (LOSCFG_KERNEL_LITEIPC == YES) taskCB->ipcStatus &= ~IPC_THREAD_STATUS_PEND; #endif taskCB->taskStatus \|= OS_TASK_STATUS_TIMEOUT; LOS_ListDelete(&taskCB->pendList); taskCB->taskSem = NULL; taskCB->taskMux = NULL; } else { taskCB->taskStatus &= ~OS_TASK_STATUS_DELAY; } if (!(tempStatus & OS_TASK_STATUS_SUSPEND)) { OS_TASK_SCHED_QUEUE_ENQUEUE(taskCB, OS_PROCESS_STATUS_PEND); needSchedule = TRUE; } if (LOS_ListEmpty(listObject)) { break; } sortList = LOS_DL_LIST_ENTRY(listObject->pstNext, SortLinkList, sortLinkNode); } LOS_SpinUnlock(&g_taskSpin); if (needSchedule != FALSE) { LOS_MpSchedule(OS_MP_CPU_ALL); LOS_Schedule(); } } 复制代码* 0
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