v04.03 鸿蒙内核源码分析(任务调度) | 任务是内核调度的单元 原创

#define OS_TASK_STATUS_INIT         0x0001U
#define OS_TASK_STATUS_READY        0x0002U
#define OS_TASK_STATUS_RUNNING      0x0004U
#define OS_TASK_STATUS_SUSPEND      0x0008U
#define OS_TASK_STATUS_PEND         0x0010U
#define OS_TASK_STATUS_DELAY        0x0020U
#define OS_TASK_STATUS_TIMEOUT      0x0040U
#define OS_TASK_STATUS_PEND_TIME    0x0080U
#define OS_TASK_STATUS_EXIT         0x0100U
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typedef struct {
    VOID            *stackPointer;      /**< Task stack pointer */ //非用户模式下的栈指针
    UINT16          taskStatus;         /**< Task status */   //各种状态标签，可以拥有多种标签，按位标识
    UINT16          priority;           /**< Task priority */  //任务优先级[0:31],默认是31级
    UINT16          policy;    //任务的调度方式(三种 .. LOS_SCHED_RR )
    UINT16          timeSlice;          /**< Remaining time slice *///剩余时间片
    UINT32          stackSize;          /**< Task stack size */  //非用户模式下栈大小
    UINTPTR         topOfStack;         /**< Task stack top */  //非用户模式下的栈顶 bottom = top + size
    UINT32          taskID;             /**< Task ID */    //任务ID，任务池本质是一个大数组，ID就是数组的索引，默认 < 128
    TSK_ENTRY_FUNC  taskEntry;          /**< Task entrance function */ //任务执行入口函数
    VOID            *joinRetval;        /**< pthread adaption */ //用来存储join线程的返回值
    VOID            *taskSem;           /**< Task-held semaphore */ //task在等哪个信号量
    VOID            *taskMux;           /**< Task-held mutex */  //task在等哪把锁
    VOID            *taskEvent;         /**< Task-held event */  //task在等哪个事件
    UINTPTR         args[4];            /**< Parameter, of which the maximum number is 4 */ //入口函数的参数 例如 main (int argc,char *argv[])
    CHAR            taskName[OS_TCB_NAME_LEN]; /**< Task name */ //任务的名称
    LOS_DL_LIST     pendList;           /**< Task pend node */  //如果任务阻塞时就通过它挂到各种阻塞情况的链表上,比如OsTaskWait时
    LOS_DL_LIST     threadList;         /**< thread list */   //挂到所属进程的线程链表上
    SortLinkList    sortList;           /**< Task sortlink node */ //挂到cpu core 的任务执行链表上
    UINT32          eventMask;          /**< Event mask */   //事件屏蔽
    UINT32          eventMode;          /**< Event mode */   //事件模式
    UINT32          priBitMap;          /**< BitMap for recording the change of task priority, //任务在执行过程中优先级会经常变化，这个变量用来记录所有曾经变化
                                             the priority can not be greater than 31 */   //过的优先级，例如 ..01001011 曾经有过 0,1,3,6 优先级
    INT32           errorNo;            /**< Error Num */
    UINT32          signal;             /**< Task signal */ //任务信号类型,(SIGNAL_NONE,SIGNAL_KILL,SIGNAL_SUSPEND,SIGNAL_AFFI)
    sig_cb          sig;    //信号控制块，这里用于进程间通讯的信号,类似于 linux singal模块
#if (LOSCFG_KERNEL_SMP == YES)
    UINT16          currCpu;            /**< CPU core number of this task is running on */ //正在运行此任务的CPU内核号
    UINT16          lastCpu;            /**< CPU core number of this task is running on last time */ //上次运行此任务的CPU内核号
    UINT16          cpuAffiMask;        /**< CPU affinity mask, support up to 16 cores */ //CPU亲和力掩码，最多支持16核，亲和力很重要，多核情况下尽量一个任务在一个CPU核上运行，提高效率
    UINT32          timerCpu;           /**< CPU core number of this task is delayed or pended */ //此任务的CPU内核号被延迟或挂起
#if (LOSCFG_KERNEL_SMP_TASK_SYNC == YES)
    UINT32          syncSignal;         /**< Synchronization for signal handling */ //用于CPU之间 同步信号
#endif
#if (LOSCFG_KERNEL_SMP_LOCKDEP == YES) //死锁检测开关
    LockDep         lockDep;
#endif
#if (LOSCFG_KERNEL_SCHED_STATISTICS == YES) //调度统计开关,显然打开这个开关性能会受到影响,鸿蒙默认是关闭的
    SchedStat       schedStat;          /**< Schedule statistics */ //调度统计
#endif
#endif
    UINTPTR         userArea;   //使用区域,由运行时划定,根据运行态不同而不同
    UINTPTR         userMapBase;  //用户模式下的栈底位置
    UINT32          userMapSize;        /**< user thread stack size ,real size : userMapSize + USER_STACK_MIN_SIZE */
    UINT32          processID;          /**< Which belong process *///所属进程ID
    FutexNode       futex;    //实现快锁功能
    LOS_DL_LIST     joinList;           /**< join list */ //联结链表,允许任务之间相互释放彼此
    LOS_DL_LIST     lockList;           /**< Hold the lock list */ //拿到了哪些锁链表
    UINT32          waitID;             /**< Wait for the PID or GID of the child process */ //等待孩子的PID或GID进程
    UINT16          waitFlag;           /**< The type of child process that is waiting, belonging to a group or parent,
                                             a specific child process, or any child process */
#if (LOSCFG_KERNEL_LITEIPC == YES)
    UINT32          ipcStatus;   //IPC状态
    LOS_DL_LIST     msgListHead;  //消息队列头结点,上面挂的都是任务要读的消息
    BOOL            accessMap[LOSCFG_BASE_CORE_TSK_LIMIT];//访问图,指的是task之间是否能访问的标识,LOSCFG_BASE_CORE_TSK_LIMIT 为任务池总数
#endif
} LosTaskCB;
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LITE_OS_SEC_TEXT_INIT UINT32 OsTaskInit(VOID)
{
    UINT32 index;
    UINT32 ret;
    UINT32 size;

    g_taskMaxNum = LOSCFG_BASE_CORE_TSK_LIMIT;//任务池中最多默认128个,可谓铁打的任务池流水的线程
    size = (g_taskMaxNum + 1) * sizeof(LosTaskCB);//计算需分配内存总大小
    /*
     * This memory is resident memory and is used to save the system resources
     * of task control block and will not be freed.
     */
    g_taskCBArray = (LosTaskCB *)LOS_MemAlloc(m_aucSysMem0, size);//任务池 常驻内存,不被释放
    if (g_taskCBArray == NULL) {
        return LOS_ERRNO_TSK_NO_MEMORY;
    }
    (VOID)memset_s(g_taskCBArray, size, 0, size);

    LOS_ListInit(&g_losFreeTask);//空闲任务链表
    LOS_ListInit(&g_taskRecyleList);//需回收任务链表
    for (index = 0; index < g_taskMaxNum; index++) {
        g_taskCBArray[index].taskStatus = OS_TASK_STATUS_UNUSED;
        g_taskCBArray[index].taskID = index;//任务ID最大默认127
        LOS_ListTailInsert(&g_losFreeTask, &g_taskCBArray[index].pendList);//都插入空闲任务列表 
    }//注意:这里挂的是pendList节点,所以取TCB要通过 OS_TCB_FROM_PENDLIST 取.

    ret = OsPriQueueInit();//创建32个任务优先级队列，即32个双向循环链表
    if (ret != LOS_OK) {
        return LOS_ERRNO_TSK_NO_MEMORY;
    }

    /* init sortlink for each core */
    for (index = 0; index < LOSCFG_KERNEL_CORE_NUM; index++) {
        ret = OsSortLinkInit(&g_percpu[index].taskSortLink);//每个CPU内核都有一个执行任务链表
        if (ret != LOS_OK) {
            return LOS_ERRNO_TSK_NO_MEMORY;
        }
    }
    return LOS_OK;
}
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#define OS_PRIORITY_QUEUE_NUM 32
LITE_OS_SEC_BSS LOS_DL_LIST *g_priQueueList = NULL;//队列链表
LITE_OS_SEC_BSS UINT32 g_priQueueBitmap;//队列位图 UINT32每位代表一个优先级,共32个优先级
//内部队列初始化
UINT32 OsPriQueueInit(VOID)
{
    UINT32 priority;

    /* system resident resource *///常驻内存
    g_priQueueList = (LOS_DL_LIST *)LOS_MemAlloc(m_aucSysMem0, (OS_PRIORITY_QUEUE_NUM * sizeof(LOS_DL_LIST)));//分配32个队列头节点
    if (g_priQueueList == NULL) {
        return LOS_NOK;
    }

    for (priority = 0; priority < OS_PRIORITY_QUEUE_NUM; ++priority) {
        LOS_ListInit(&g_priQueueList[priority]);//队列初始化,前后指针指向自己
    }
    return LOS_OK;
}


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/* The size of this structure must be smaller than or equal to the size specified by OS_TSK_STACK_ALIGN (16 bytes). */
typedef struct {
   
#if !defined(LOSCFG_ARCH_FPU_DISABLE)
    UINT64 D[FP_REGS_NUM]; /* D0-D31 */
    UINT32 regFPSCR;       /* FPSCR */
    UINT32 regFPEXC;       /* FPEXC */
#endif
    UINT32 resved;          /* It's stack 8 aligned */
    UINT32 regPSR;
    UINT32 R[GEN_REGS_NUM]; /* R0-R12 */
    UINT32 SP;              /* R13 */
    UINT32 LR;              /* R14 */
    UINT32 PC;              /* R15 */
} TaskContext;
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LITE_OS_SEC_TEXT_INIT VOID *OsTaskStackInit(UINT32 taskID, UINT32 stackSize, VOID *topStack, BOOL initFlag)
{
   
    UINT32 index = 1;
    TaskContext *taskContext = NULL;

    if (initFlag == TRUE) {
   
        OsStackInit(topStack, stackSize);
    }
    taskContext = (TaskContext *)(((UINTPTR)topStack + stackSize) - sizeof(TaskContext));//注意看上下文将存放在栈的底部

    /* initialize the task context */
#ifdef LOSCFG_GDB
    taskContext->PC = (UINTPTR)OsTaskEntrySetupLoopFrame;
#else
    taskContext->PC = (UINTPTR)OsTaskEntry;//程序计数器,CPU首次执行task时跑的第一条指令位置
#endif
    taskContext->LR = (UINTPTR)OsTaskExit;  /* LR should be kept, to distinguish it's THUMB or ARM instruction */
    taskContext->resved = 0x0;
    taskContext->R[0] = taskID;             /* R0 */
    taskContext->R[index++] = 0x01010101;   /* R1, 0x01010101 : reg initialed magic word */
    for (; index < GEN_REGS_NUM; index++) {
   //R2 - R12的初始化很有意思,为什么要这么做？
        taskContext->R[index] = taskContext->R[index - 1] + taskContext->R[1]; /* R2 - R12 */
    }

#ifdef LOSCFG_INTERWORK_THUMB // 16位模式
    taskContext->regPSR = PSR_MODE_SVC_THUMB; /* CPSR (Enable IRQ and FIQ interrupts, THUMNB-mode) */
#else
    taskContext->regPSR = PSR_MODE_SVC_ARM;   /* CPSR (Enable IRQ and FIQ interrupts, ARM-mode) */
#endif

#if !defined(LOSCFG_ARCH_FPU_DISABLE)
    /* 0xAAA0000000000000LL : float reg initialed magic word */
    for (index = 0; index < FP_REGS_NUM; index++) {
   
        taskContext->D[index] = 0xAAA0000000000000LL + index; /* D0 - D31 */
    }
    taskContext->regFPSCR = 0;
    taskContext->regFPEXC = FP_EN;
#endif

    return (VOID *)taskContext;
}
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typedef struct tagTskInitParam {//Task的初始化参数
    TSK_ENTRY_FUNC  pfnTaskEntry;  /**< Task entrance function */ //任务的入口函数
    UINT16          usTaskPrio;    /**< Task priority */ //任务优先级
    UINT16          policy;        /**< Task policy */  //任务调度方式
    UINTPTR         auwArgs[4];    /**< Task parameters, of which the maximum number is four */ //入口函数的参数,最多四个
    UINT32          uwStackSize;   /**< Task stack size */ //任务栈大小
    CHAR            *pcName;       /**< Task name */  //任务名称
#if (LOSCFG_KERNEL_SMP == YES)
    UINT16          usCpuAffiMask; /**< Task cpu affinity mask         */ //任务cpu亲和力掩码
#endif
    UINT32          uwResved;      /**< It is automatically deleted if set to LOS_TASK_STATUS_DETACHED.
                                        It is unable to be deleted if set to 0. */ //如果设置为LOS_TASK_STATUS_DETACHED，则自动删除。如果设置为0，则无法删除
    UINT16          consoleID;     /**< The console id of task belongs  */ //任务的控制台id所属
    UINT32          processID; //进程ID
    UserTaskParam   userParam; //在用户态运行时栈参数
} TSK_INIT_PARAM_S;
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u32_t osShellPing(int argc, const char **argv)
{
   
    int ret;
    u32_t i = 0;
    u32_t count = 0;
    int count_set = 0;
    u32_t interval = 1000; /* default ping interval */
    u32_t data_len = 48; /* default data length */
    ip4_addr_t dst_ipaddr;
    TSK_INIT_PARAM_S stPingTask;
    // ...省去一些中间代码
    /* start one task if ping forever or ping count greater than 60 */
    if (count == 0 || count > LWIP_SHELL_CMD_PING_RETRY_TIMES) {
   
        if (ping_taskid > 0) {
   
            PRINTK("Ping task already running and only support one now\n");
            return LOS_NOK;
        }
        stPingTask.pfnTaskEntry = (TSK_ENTRY_FUNC)ping_cmd;//线程的执行函数
        stPingTask.uwStackSize = LOSCFG_BASE_CORE_TSK_DEFAULT_STACK_SIZE;//0x4000 = 16K 
        stPingTask.pcName = "ping_task";
        stPingTask.usTaskPrio = 8; /* higher than shell 优先级高于10,属于内核态线程*/ 
        stPingTask.uwResved = LOS_TASK_STATUS_DETACHED;
        stPingTask.auwArgs[0] = dst_ipaddr.addr; /* network order */
        stPingTask.auwArgs[1] = count;
        stPingTask.auwArgs[2] = interval;
        stPingTask.auwArgs[3] = data_len;
        ret = LOS_TaskCreate((UINT32 *)(&ping_taskid), &stPingTask);
    }
 // ...
    return LOS_OK;
ping_error:
    lwip_ping_usage();
    return LOS_NOK;
}
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LITE_OS_SEC_TEXT_MINOR UINT32 ShellTaskInit(ShellCB *shellCB)
{
   
    CHAR *name = NULL;
    TSK_INIT_PARAM_S initParam = {
   0};
    if (shellCB->consoleID == CONSOLE_SERIAL) {
   
        name = SERIAL_SHELL_TASK_NAME;
    } else if (shellCB->consoleID == CONSOLE_TELNET) {
   
        name = TELNET_SHELL_TASK_NAME;
    } else {
   
        return LOS_NOK;
    }
    initParam.pfnTaskEntry = (TSK_ENTRY_FUNC)ShellTask;
    initParam.usTaskPrio   = 9; /* 9:shell task priority */
    initParam.auwArgs[0]   = (UINTPTR)shellCB;
    initParam.uwStackSize  = 0x3000;
    initParam.pcName       = name;
    initParam.uwResved     = LOS_TASK_STATUS_DETACHED;
    (VOID)LOS_EventInit(&shellCB->shellEvent);
    return LOS_TaskCreate(&shellCB->shellTaskHandle, &initParam);
}
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//创建Task
LITE_OS_SEC_TEXT_INIT UINT32 LOS_TaskCreate(UINT32 *taskID, TSK_INIT_PARAM_S *initParam)
{
    UINT32 ret;
    UINT32 intSave;
    LosTaskCB *taskCB = NULL;

    if (initParam == NULL) {
        return LOS_ERRNO_TSK_PTR_NULL;
    }

    if (OS_INT_ACTIVE) {
        return LOS_ERRNO_TSK_YIELD_IN_INT;
    }

    if (initParam->uwResved & OS_TASK_FLAG_IDLEFLAG) {//OS_TASK_FLAG_IDLEFLAG 是属于内核 idle进程专用的
        initParam->processID = OsGetIdleProcessID();//获取空闲进程
    } else if (OsProcessIsUserMode(OsCurrProcessGet())) {//当前进程是否为用户模式
        initParam->processID = OsGetKernelInitProcessID();//不是就取"Kernel"进程
    } else {
        initParam->processID = OsCurrProcessGet()->processID;//获取当前进程 ID赋值
    }
    initParam->uwResved &= ~OS_TASK_FLAG_IDLEFLAG;//不能是 OS_TASK_FLAG_IDLEFLAG
    initParam->uwResved &= ~OS_TASK_FLAG_PTHREAD_JOIN;//不能是 OS_TASK_FLAG_PTHREAD_JOIN
    if (initParam->uwResved & LOS_TASK_STATUS_DETACHED) {//是否设置了自动删除
        initParam->uwResved = OS_TASK_FLAG_DETACHED;//自动删除,注意这里是 = ,也就是说只有 OS_TASK_FLAG_DETACHED 一个标签了
    }

    ret = LOS_TaskCreateOnly(taskID, initParam);//创建一个任务,这是任务创建的实体,前面都只是前期准备工作
    if (ret != LOS_OK) {
        return ret;
    }
    taskCB = OS_TCB_FROM_TID(*taskID);//通过ID拿到task实体

    SCHEDULER_LOCK(intSave);
    taskCB->taskStatus &= ~OS_TASK_STATUS_INIT;//任务不再是初始化
    OS_TASK_SCHED_QUEUE_ENQUEUE(taskCB, 0);//进入调度就绪队列,新任务是直接进入就绪队列的
    SCHEDULER_UNLOCK(intSave);

    /* in case created task not running on this core,
       schedule or not depends on other schedulers status. */
    LOS_MpSchedule(OS_MP_CPU_ALL);//如果创建的任务没有在这个核心上运行，是否调度取决于其他调度程序的状态。
    if (OS_SCHEDULER_ACTIVE) {//当前CPU核处于可调度状态
        LOS_Schedule();//发起调度
    }

    return LOS_OK;
}
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