SmartPDCode/truing_control/PDU-AC-235-NEW/FreeRTOS/tasks.c

/*
 * FreeRTOS Kernel V10.5.1
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/* Standard includes. */
#include <stdlib.h>
#include <string.h>

/* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
 * all the API functions to use the MPU wrappers.  That should only be done when
 * task.h is included from an application file. */
#define MPU_WRAPPERS_INCLUDED_FROM_API_FILE

/* FreeRTOS includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "timers.h"
#include "stack_macros.h"

/* Lint e9021, e961 and e750 are suppressed as a MISRA exception justified
 * because the MPU ports require MPU_WRAPPERS_INCLUDED_FROM_API_FILE to be defined
 * for the header files above, but not in this file, in order to generate the
 * correct privileged Vs unprivileged linkage and placement. */
#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE /*lint !e961 !e750 !e9021. */

/* Set configUSE_STATS_FORMATTING_FUNCTIONS to 2 to include the stats formatting
 * functions but without including stdio.h here. */
#if (configUSE_STATS_FORMATTING_FUNCTIONS == 1)

/* At the bottom of this file are two optional functions that can be used
 * to generate human readable text from the raw data generated by the
 * uxTaskGetSystemState() function.  Note the formatting functions are provided
 * for convenience only, and are NOT considered part of the kernel. */
    #include <stdio.h>
#endif /* configUSE_STATS_FORMATTING_FUNCTIONS == 1) */

#if (configUSE_PREEMPTION == 0)

/* If the cooperative scheduler is being used then a yield should not be
 * performed just because a higher priority task has been woken. */
    #define taskYIELD_IF_USING_PREEMPTION()
#else
    #define taskYIELD_IF_USING_PREEMPTION()    portYIELD_WITHIN_API()
#endif

/**
 * Values that can be assigned to the ucNotifyState member of the TCB.
 * 接收任务通知状态机
 */
#define taskNOT_WAITING_NOTIFICATION              ((uint8_t)0)
#define taskWAITING_NOTIFICATION                  ((uint8_t)1)
#define taskNOTIFICATION_RECEIVED                 ((uint8_t)2)

/*
 * The value used to fill the stack of a task when the task is created.  This
 * is used purely for checking the high water mark for tasks.
 */
#define tskSTACK_FILL_BYTE                        (0xa5U)

/* Bits used to record how a task's stack and TCB were allocated. */
#define tskDYNAMICALLY_ALLOCATED_STACK_AND_TCB    ((uint8_t) 0)
#define tskSTATICALLY_ALLOCATED_STACK_ONLY        ((uint8_t) 1)
#define tskSTATICALLY_ALLOCATED_STACK_AND_TCB     ((uint8_t) 2)

/* If any of the following are set then task stacks are filled with a known
 * value so the high water mark can be determined.  If none of the following are
 * set then don't fill the stack so there is no unnecessary dependency on memset. */
#if ((configCHECK_FOR_STACK_OVERFLOW > 1) || \
    (configUSE_TRACE_FACILITY == 1) || \
    (INCLUDE_uxTaskGetStackHighWaterMark == 1) || \
    (INCLUDE_uxTaskGetStackHighWaterMark2 == 1))

    #define tskSET_NEW_STACKS_TO_KNOWN_VALUE    1
#else
    #define tskSET_NEW_STACKS_TO_KNOWN_VALUE    0
#endif

/*
 * Macros used by vListTask to indicate which state a task is in.
 */
#define tskRUNNING_CHAR      ('X')
#define tskBLOCKED_CHAR      ('B')
#define tskREADY_CHAR        ('R')
#define tskDELETED_CHAR      ('D')
#define tskSUSPENDED_CHAR    ('S')

/*
 * Some kernel aware debuggers require the data the debugger needs access to to
 * be global, rather than file scope.
 */
#ifdef portREMOVE_STATIC_QUALIFIER
    #define static
#endif

/* The name allocated to the Idle task.  This can be overridden by defining
 * configIDLE_TASK_NAME in FreeRTOSConfig.h. */
#ifndef configIDLE_TASK_NAME
    #define configIDLE_TASK_NAME    "IDLE"
#endif

#if (configUSE_PORT_OPTIMISED_TASK_SELECTION == 0)

/* If configUSE_PORT_OPTIMISED_TASK_SELECTION is 0 then task selection is
 * performed in a generic way that is not optimised to any particular
 * microcontroller architecture. */

/* uxTopReadyPriority holds the priority of the highest priority ready
 * state task. */
    #define taskRECORD_READY_PRIORITY(uxPriority) \
    {                                               \
        if ((uxPriority) > uxTopReadyPriority)   \
        {                                           \
            uxTopReadyPriority = (uxPriority);    \
        }                                           \
    } /* taskRECORD_READY_PRIORITY */



    #define taskSELECT_HIGHEST_PRIORITY_TASK()                                \
    {                                                                         \
        UBaseType_t uxTopPriority = uxTopReadyPriority;                       \
                                                                              \
        /* Find the highest priority queue that contains ready tasks. */      \
        while (listLIST_IS_EMPTY(&(pxReadyTasksLists[uxTopPriority]))) \
        {                                                                     \
            configASSERT(uxTopPriority);                                    \
            --uxTopPriority;                                                  \
        }                                                                     \
                                                                              \
        /* listGET_OWNER_OF_NEXT_ENTRY indexes through the list, so the tasks of \
         * the  same priority get an equal share of the processor time. */                    \
        listGET_OWNER_OF_NEXT_ENTRY(pxCurrentTCB, &(pxReadyTasksLists[uxTopPriority])); \
        uxTopReadyPriority = uxTopPriority;                                                   \
    } /* taskSELECT_HIGHEST_PRIORITY_TASK */


/* Define away taskRESET_READY_PRIORITY() and portRESET_READY_PRIORITY() as
 * they are only required when a port optimised method of task selection is
 * being used. */
    #define taskRESET_READY_PRIORITY(uxPriority)
    #define portRESET_READY_PRIORITY(uxPriority, uxTopReadyPriority)

#else /* configUSE_PORT_OPTIMISED_TASK_SELECTION */

/* If configUSE_PORT_OPTIMISED_TASK_SELECTION is 1 then task selection is
 * performed in a way that is tailored to the particular microcontroller
 * architecture being used. */

/* A port optimised version is provided.  Call the port defined macros. */
#define taskRECORD_READY_PRIORITY(uxPriority)    portRECORD_READY_PRIORITY((uxPriority), uxTopReadyPriority)


/**
 * 找到优先级最高的任务
 * pxCurrentTCB 保存优先级最高的任务
 * @uxTopPriority: 保存当前系统最高优先级
 */
#define taskSELECT_HIGHEST_PRIORITY_TASK()                                                 \
{                                                                                          \
    UBaseType_t uxTopPriority;                                                             \
                                                                                           \
    /* Find the highest priority list that contains ready tasks. */                        \
    portGET_HIGHEST_PRIORITY(uxTopPriority, uxTopReadyPriority);                          \
    configASSERT(listCURRENT_LIST_LENGTH(&(pxReadyTasksLists[uxTopPriority])) > 0);        \
    listGET_OWNER_OF_NEXT_ENTRY(pxCurrentTCB, &(pxReadyTasksLists[uxTopPriority]));       \
} /* taskSELECT_HIGHEST_PRIORITY_TASK() */


/* A port optimised version is provided, call it only if the TCB being reset
 * is being referenced from a ready list.  If it is referenced from a delayed
 * or suspended list then it won't be in a ready list. */
    #define taskRESET_READY_PRIORITY(uxPriority)                                                     \
    {                                                                                                  \
        if (listCURRENT_LIST_LENGTH(&(pxReadyTasksLists[(uxPriority)])) == (UBaseType_t) 0) \
        {                                                                                              \
            portRESET_READY_PRIORITY((uxPriority), (uxTopReadyPriority));                        \
        }                                                                                              \
    }

#endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */


/**
 * pxDelayedTaskList and pxOverflowDelayedTaskList are switched when the tick
 * count overflows.
 * 当xTickCount溢出时候，交换pxDelayedTaskList和pxOverflowDelayedTaskList队列
 */
#define taskSWITCH_DELAYED_LISTS()                                                \
    {                                                                             \
        List_t * pxTemp;                                                          \
                                                                                  \
        /* The delayed tasks list should be empty when the lists are switched. */ \
        configASSERT((listLIST_IS_EMPTY(pxDelayedTaskList)));               \
                                                                                  \
        pxTemp = pxDelayedTaskList;                                               \
        pxDelayedTaskList = pxOverflowDelayedTaskList;                            \
        pxOverflowDelayedTaskList = pxTemp;                                       \
        xNumOfOverflows++;                                                        \
        prvResetNextTaskUnblockTime();                                            \
    }

/*
 * Place the task represented by pxTCB into the appropriate ready list for
 * the task.  It is inserted at the end of the list.
 * 相同优先级的，使用队列方式加入
 */
#define prvAddTaskToReadyList(pxTCB)                                                       \
    traceMOVED_TASK_TO_READY_STATE(pxTCB);                                                 \
    taskRECORD_READY_PRIORITY((pxTCB)->uxPriority);                                        \
    listINSERT_END(&(pxReadyTasksLists[(pxTCB)->uxPriority]), &((pxTCB)->xStateListItem)); \
    tracePOST_MOVED_TASK_TO_READY_STATE(pxTCB)

/*
 * Several functions take a TaskHandle_t parameter that can optionally be NULL,
 * where NULL is used to indicate that the handle of the currently executing
 * task should be used in place of the parameter.  This macro simply checks to
 * see if the parameter is NULL and returns a pointer to the appropriate TCB.
 */
#define prvGetTCBFromHandle(pxHandle)    (((pxHandle) == NULL) ? pxCurrentTCB : (pxHandle))

/* The item value of the event list item is normally used to hold the priority
 * of the task to which it belongs (coded to allow it to be held in reverse
 * priority order).  However, it is occasionally borrowed for other purposes.  It
 * is important its value is not updated due to a task priority change while it is
 * being used for another purpose.  The following bit definition is used to inform
 * the scheduler that the value should not be changed - in which case it is the
 * responsibility of whichever module is using the value to ensure it gets set back
 * to its original value when it is released. */
#if (configUSE_16_BIT_TICKS == 1)
    #define taskEVENT_LIST_ITEM_VALUE_IN_USE    0x8000U
#else
    #define taskEVENT_LIST_ITEM_VALUE_IN_USE    0x80000000UL
#endif

/*
 * Task control block.  A task control block (TCB) is allocated for each task,
 * and stores task state information, including a pointer to the task's context
 * (the task's run time environment, including register values)
 * 任务控制块
 */
typedef struct tskTaskControlBlock
{
    volatile StackType_t * pxTopOfStack; /*THIS MUST BE THE FIRST MEMBER OF THE TCB STRUCT. */

    #if (portUSING_MPU_WRAPPERS == 1)
        xMPU_SETTINGS xMPUSettings; /*THIS MUST BE THE SECOND MEMBER OF THE TCB STRUCT. */
    #endif

    ListItem_t xStateListItem;                  /* 任务状态队列节点 (Ready, Blocked, Suspended). */
    ListItem_t xEventListItem;                  /* 任务事件队列节点 */
    UBaseType_t uxPriority;                     /* 任务优先级 */
    StackType_t * pxStack;                      /* 任务栈顶 */
    char pcTaskName[configMAX_TASK_NAME_LEN];

/* Points to the highest valid address for the stack. */
#if ((portSTACK_GROWTH > 0) || (configRECORD_STACK_HIGH_ADDRESS == 1))
    StackType_t * pxEndOfStack;
#endif

/* Holds the critical section nesting depth for ports
 * that do not maintain their own count in the port layer.
 */
#if (portCRITICAL_NESTING_IN_TCB == 1)
    UBaseType_t uxCriticalNesting;
#endif

#if (configUSE_TRACE_FACILITY == 1)
    UBaseType_t uxTCBNumber;
    UBaseType_t uxTaskNumber;
#endif

#if (configUSE_MUTEXES == 1)
    UBaseType_t uxBasePriority;
    UBaseType_t uxMutexesHeld;
#endif

#if (configUSE_APPLICATION_TASK_TAG == 1)
    TaskHookFunction_t pxTaskTag;
#endif

#if (configNUM_THREAD_LOCAL_STORAGE_POINTERS > 0)
    void * pvThreadLocalStoragePointers[configNUM_THREAD_LOCAL_STORAGE_POINTERS];
#endif

/* Stores the amount of time the task has spent in the Running state. */
#if (configGENERATE_RUN_TIME_STATS == 1)
    configRUN_TIME_COUNTER_TYPE ulRunTimeCounter;
#endif

/* Memory block used as Thread Local Storage (TLS) Block for the task. */
#if ((configUSE_NEWLIB_REENTRANT == 1) || (configUSE_C_RUNTIME_TLS_SUPPORT == 1))
    configTLS_BLOCK_TYPE xTLSBlock;
#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)
    volatile uint32_t ulNotifiedValue[configTASK_NOTIFICATION_ARRAY_ENTRIES];
    volatile uint8_t ucNotifyState[configTASK_NOTIFICATION_ARRAY_ENTRIES];
#endif

    /* See the comments in FreeRTOS.h with the definition of
     * tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE. */
#if (tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE != 0)
    uint8_t ucStaticallyAllocated;
#endif

#if (INCLUDE_xTaskAbortDelay == 1)
        uint8_t ucDelayAborted;
#endif

#if (configUSE_POSIX_ERRNO == 1)
        int iTaskErrno;
#endif
} tskTCB;

/* The old tskTCB name is maintained above then typedefed to the new TCB_t name
 * below to enable the use of older kernel aware debuggers.
 */
typedef tskTCB TCB_t;

/*lint -save -e956 A manual analysis and inspection has been used to determine
 * which static variables must be declared volatile. */
portDONT_DISCARD PRIVILEGED_DATA TCB_t * volatile pxCurrentTCB = NULL;

/**
 * Lists for ready and blocked tasks. --------------------
 * xDelayedTaskList1 and xDelayedTaskList2 could be moved to function scope but
 * doing so breaks some kernel aware debuggers and debuggers that rely on removing
 * the static qualifier.
 * @pxReadyTasksLists: 就绪任务管理数组,每一个优先级拥有自己的管理队列
 */
PRIVILEGED_DATA static List_t pxReadyTasksLists[configMAX_PRIORITIES]; /*< Prioritised ready tasks. */
PRIVILEGED_DATA static List_t xDelayedTaskList1;                         /*< Delayed tasks. */
PRIVILEGED_DATA static List_t xDelayedTaskList2;                         /*< Delayed tasks (two lists are used - one for delays that have overflowed the current tick count. */
PRIVILEGED_DATA static List_t * volatile pxDelayedTaskList;              /*< Points to the delayed task list currently being used. */
PRIVILEGED_DATA static List_t * volatile pxOverflowDelayedTaskList;      /*< Points to the delayed task list currently being used to hold tasks that have overflowed the current tick count. */
PRIVILEGED_DATA static List_t xPendingReadyList;                         /*< Tasks that have been readied while the scheduler was suspended.  They will be moved to the ready list when the scheduler is resumed. */

#if (INCLUDE_vTaskDelete == 1)

    PRIVILEGED_DATA static List_t xTasksWaitingTermination; /*< Tasks that have been deleted - but their memory not yet freed. */
    PRIVILEGED_DATA static volatile UBaseType_t uxDeletedTasksWaitingCleanUp = (UBaseType_t) 0U;

#endif

#if (INCLUDE_vTaskSuspend == 1)

    PRIVILEGED_DATA static List_t xSuspendedTaskList; /*< Tasks that are currently suspended. */

#endif

/* Global POSIX errno. Its value is changed upon context switching to match
 * the errno of the currently running task. */
#if (configUSE_POSIX_ERRNO == 1)
    int FreeRTOS_errno = 0;
#endif

/* Other file private variables. --------------------------------*/
PRIVILEGED_DATA static volatile UBaseType_t uxCurrentNumberOfTasks = (UBaseType_t) 0U;
/**
 * @xTickCount: 当前系统tick计数器
 */
PRIVILEGED_DATA static volatile TickType_t xTickCount = (TickType_t) configINITIAL_TICK_COUNT;
PRIVILEGED_DATA static volatile UBaseType_t uxTopReadyPriority = tskIDLE_PRIORITY;
PRIVILEGED_DATA static volatile BaseType_t xSchedulerRunning = pdFALSE;
PRIVILEGED_DATA static volatile TickType_t xPendedTicks = (TickType_t) 0U;
PRIVILEGED_DATA static volatile BaseType_t xYieldPending = pdFALSE;
/**
 * @xNumOfOverflows: 记录xTickCount溢出的次数
 */
PRIVILEGED_DATA static volatile BaseType_t xNumOfOverflows = (BaseType_t) 0;
PRIVILEGED_DATA static UBaseType_t uxTaskNumber = (UBaseType_t) 0U;
PRIVILEGED_DATA static volatile TickType_t xNextTaskUnblockTime = (TickType_t) 0U; /* Initialised to portMAX_DELAY before the scheduler starts. */
/**
 * 空闲任务描述符
 */
PRIVILEGED_DATA static TaskHandle_t xIdleTaskHandle = NULL;

/* Improve support for OpenOCD. The kernel tracks Ready tasks via priority lists.
 * For tracking the state of remote threads, OpenOCD uses uxTopUsedPriority
 * to determine the number of priority lists to read back from the remote target. */
const volatile UBaseType_t uxTopUsedPriority = configMAX_PRIORITIES - 1U;

/* Context switches are held pending while the scheduler is suspended.  Also,
 * interrupts must not manipulate the xStateListItem of a TCB, or any of the
 * lists the xStateListItem can be referenced from, if the scheduler is suspended.
 * If an interrupt needs to unblock a task while the scheduler is suspended then it
 * moves the task's event list item into the xPendingReadyList, ready for the
 * kernel to move the task from the pending ready list into the real ready list
 * when the scheduler is unsuspended.  The pending ready list itself can only be
 * accessed from a critical section. */
PRIVILEGED_DATA static volatile UBaseType_t uxSchedulerSuspended = (UBaseType_t) pdFALSE;

#if (configGENERATE_RUN_TIME_STATS == 1)

/* Do not move these variables to function scope as doing so prevents the
 * code working with debuggers that need to remove the static qualifier. */
    PRIVILEGED_DATA static configRUN_TIME_COUNTER_TYPE ulTaskSwitchedInTime = 0UL;    /*< Holds the value of a timer/counter the last time a task was switched in. */
    PRIVILEGED_DATA static volatile configRUN_TIME_COUNTER_TYPE ulTotalRunTime = 0UL; /*< Holds the total amount of execution time as defined by the run time counter clock. */

#endif

/**
 * Utility task that simply returns pdTRUE if the task referenced by xTask is
 * currently in the Suspended state, or pdFALSE if the task referenced by xTask
 * is in any other state.
 */
#if (INCLUDE_vTaskSuspend == 1)

    static BaseType_t prvTaskIsTaskSuspended(const TaskHandle_t xTask) PRIVILEGED_FUNCTION;

#endif /* INCLUDE_vTaskSuspend */

/*
 * Utility to ready all the lists used by the scheduler.  This is called
 * automatically upon the creation of the first task.
 */
static void prvInitialiseTaskLists(void) PRIVILEGED_FUNCTION;

/*
 * The idle task, which as all tasks is implemented as a never ending loop.
 * The idle task is automatically created and added to the ready lists upon
 * creation of the first user task.
 *
 * The portTASK_FUNCTION_PROTO() macro is used to allow port/compiler specific
 * language extensions.  The equivalent prototype for this function is:
 *
 * void prvIdleTask(void *pvParameters);
 *
 */
static portTASK_FUNCTION_PROTO(prvIdleTask, pvParameters) PRIVILEGED_FUNCTION;

/*
 * Utility to free all memory allocated by the scheduler to hold a TCB,
 * including the stack pointed to by the TCB.
 *
 * This does not free memory allocated by the task itself (i.e. memory
 * allocated by calls to pvPortMalloc from within the tasks application code).
 */
#if (INCLUDE_vTaskDelete == 1)

    static void prvDeleteTCB(TCB_t * pxTCB) PRIVILEGED_FUNCTION;

#endif

/*
 * Used only by the idle task.  This checks to see if anything has been placed
 * in the list of tasks waiting to be deleted.  If so the task is cleaned up
 * and its TCB deleted.
 */
static void prvCheckTasksWaitingTermination(void) PRIVILEGED_FUNCTION;

/*
 * The currently executing task is entering the Blocked state.  Add the task to
 * either the current or the overflow delayed task list.
 */
static void prvAddCurrentTaskToDelayedList(TickType_t xTicksToWait,
                                            const BaseType_t xCanBlockIndefinitely) PRIVILEGED_FUNCTION;

/*
 * Fills an TaskStatus_t structure with information on each task that is
 * referenced from the pxList list (which may be a ready list, a delayed list,
 * a suspended list, etc.).
 *
 * THIS FUNCTION IS INTENDED FOR DEBUGGING ONLY, AND SHOULD NOT BE CALLED FROM
 * NORMAL APPLICATION CODE.
 */
#if (configUSE_TRACE_FACILITY == 1)

    static UBaseType_t prvListTasksWithinSingleList(TaskStatus_t * pxTaskStatusArray,
                                                     List_t * pxList,
                                                     eTaskState eState) PRIVILEGED_FUNCTION;

#endif

/*
 * Searches pxList for a task with name pcNameToQuery - returning a handle to
 * the task if it is found, or NULL if the task is not found.
 */
#if (INCLUDE_xTaskGetHandle == 1)

    static TCB_t * prvSearchForNameWithinSingleList(List_t * pxList,
                                                     const char pcNameToQuery[]) PRIVILEGED_FUNCTION;

#endif

/*
 * When a task is created, the stack of the task is filled with a known value.
 * This function determines the 'high water mark' of the task stack by
 * determining how much of the stack remains at the original preset value.
 */
#if ((configUSE_TRACE_FACILITY == 1) || (INCLUDE_uxTaskGetStackHighWaterMark == 1) || (INCLUDE_uxTaskGetStackHighWaterMark2 == 1))

    static configSTACK_DEPTH_TYPE prvTaskCheckFreeStackSpace(const uint8_t * pucStackByte) PRIVILEGED_FUNCTION;

#endif

/*
 * Return the amount of time, in ticks, that will pass before the kernel will
 * next move a task from the Blocked state to the Running state.
 *
 * This conditional compilation should use inequality to 0, not equality to 1.
 * This is to ensure portSUPPRESS_TICKS_AND_SLEEP() can be called when user
 * defined low power mode implementations require configUSE_TICKLESS_IDLE to be
 * set to a value other than 1.
 */
#if (configUSE_TICKLESS_IDLE != 0)

    static TickType_t prvGetExpectedIdleTime(void) PRIVILEGED_FUNCTION;

#endif

/*
 * Set xNextTaskUnblockTime to the time at which the next Blocked state task
 * will exit the Blocked state.
 */
static void prvResetNextTaskUnblockTime(void) PRIVILEGED_FUNCTION;

#if (configUSE_STATS_FORMATTING_FUNCTIONS > 0)

/*
 * Helper function used to pad task names with spaces when printing out
 * human readable tables of task information.
 */
    static char * prvWriteNameToBuffer(char * pcBuffer,
                                        const char * pcTaskName) PRIVILEGED_FUNCTION;

#endif

/*
 * Called after a Task_t structure has been allocated either statically or
 * dynamically to fill in the structure's members.
 */
static void prvInitialiseNewTask(TaskFunction_t pxTaskCode,
                                  const char * const pcName,
                                  const uint32_t ulStackDepth,
                                  void * const pvParameters,
                                  UBaseType_t uxPriority,
                                  TaskHandle_t * const pxCreatedTask,
                                  TCB_t * pxNewTCB,
                                  const MemoryRegion_t * const xRegions) PRIVILEGED_FUNCTION;

/*
 * Called after a new task has been created and initialised to place the task
 * under the control of the scheduler.
 */
static void prvAddNewTaskToReadyList(TCB_t * pxNewTCB) PRIVILEGED_FUNCTION;

/*
 * freertos_tasks_c_additions_init() should only be called if the user definable
 * macro FREERTOS_TASKS_C_ADDITIONS_INIT() is defined, as that is the only macro
 * called by the function.
 */
#ifdef FREERTOS_TASKS_C_ADDITIONS_INIT

    static void freertos_tasks_c_additions_init(void) PRIVILEGED_FUNCTION;

#endif

#if (portUSING_MPU_WRAPPERS == 1)

    BaseType_t xTaskCreateRestricted(const TaskParameters_t * const pxTaskDefinition,
                                      TaskHandle_t * pxCreatedTask)
    {
        TCB_t * pxNewTCB;
        BaseType_t xReturn = errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY;

        configASSERT(pxTaskDefinition->puxStackBuffer);

        if (pxTaskDefinition->puxStackBuffer != NULL)
        {
            /* Allocate space for the TCB.  Where the memory comes from depends
             * on the implementation of the port malloc function and whether or
             * not static allocation is being used. */
            pxNewTCB = (TCB_t *) pvPortMalloc(sizeof(TCB_t));

            if (pxNewTCB != NULL)
            {
                memset((void *) pxNewTCB, 0x00, sizeof(TCB_t));

                /* Store the stack location in the TCB. */
                pxNewTCB->pxStack = pxTaskDefinition->puxStackBuffer;

                #if (tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE != 0)
                {
                    /* Tasks can be created statically or dynamically, so note
                     * this task had a statically allocated stack in case it is
                     * later deleted.  The TCB was allocated dynamically. */
                    pxNewTCB->ucStaticallyAllocated = tskSTATICALLY_ALLOCATED_STACK_ONLY;
                }
                #endif /* tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE */

                prvInitialiseNewTask(pxTaskDefinition->pvTaskCode,
                                      pxTaskDefinition->pcName,
                                      (uint32_t) pxTaskDefinition->usStackDepth,
                                      pxTaskDefinition->pvParameters,
                                      pxTaskDefinition->uxPriority,
                                      pxCreatedTask, pxNewTCB,
                                      pxTaskDefinition->xRegions);

                prvAddNewTaskToReadyList(pxNewTCB);
                xReturn = pdPASS;
            }
        }

        return xReturn;
    }

#endif /* portUSING_MPU_WRAPPERS */

/**
 * 创建任务
 * @pxTaskCode: 任务函数入口
 * @pcName： 任务名称
 * @usStackDepth: 任务堆栈大小
 * @pvParameters: 传递给任务的参数
 * @uxPriority： 任务优先级, 数字越大，优先级越大
 * @pxCreatedTask: 任务句柄
 */
BaseType_t xTaskCreate(TaskFunction_t pxTaskCode,
                        const char * const pcName,
                        const configSTACK_DEPTH_TYPE usStackDepth,
                        void * const pvParameters,
                        UBaseType_t uxPriority,
                        TaskHandle_t * const pxCreatedTask)
{
    TCB_t * pxNewTCB;
    BaseType_t xReturn;
    /* If the stack grows down then allocate the stack then the TCB so the stack
     * does not grow into the TCB.  Likewise if the stack grows up then allocate
     * the TCB then the stack.
     * 堆栈向下生长
     */
    #if (portSTACK_GROWTH > 0)
    {
        /* Allocate space for the TCB.  Where the memory comes from depends on
         * the implementation of the port malloc function and whether or not static
         * allocation is being used. */
        pxNewTCB = (TCB_t *) pvPortMalloc(sizeof(TCB_t));
        if (pxNewTCB != NULL)
        {
            memset((void *) pxNewTCB, 0x00, sizeof(TCB_t));
            /* Allocate space for the stack used by the task being created.
             * The base of the stack memory stored in the TCB so the task can
             * be deleted later if required. */
            pxNewTCB->pxStack = (StackType_t *) pvPortMallocStack((((size_t) usStackDepth) * sizeof(StackType_t)));
            if (pxNewTCB->pxStack == NULL)
            {
                /* Could not allocate the stack.  Delete the allocated TCB. */
                vPortFree(pxNewTCB);
                pxNewTCB = NULL;
            }
        }
    }
    #else /* portSTACK_GROWTH */
    {
        StackType_t * pxStack;
        /**
         * Allocate space for the stack used by the task being created.
         * 申请任务堆栈空间
         */
        pxStack = pvPortMallocStack((((size_t)usStackDepth) * sizeof(StackType_t)));
        if (pxStack != NULL) {
            /**
             * Allocate space for the TCB.
             * 任务控制块申请内存
             */
            pxNewTCB = (TCB_t *)pvPortMalloc(sizeof(TCB_t));
            if (pxNewTCB != NULL) {
                memset((void *)pxNewTCB, 0x00, sizeof(TCB_t));
                /**
                 * Store the stack location in the TCB.
                 * 设置新任务的堆栈
                 */
                pxNewTCB->pxStack = pxStack;
            }
            else
            {
                /* The stack cannot be used as the TCB was not created.  Free
                 * it again. */
                vPortFreeStack(pxStack);
            }
        }
        else
        {
            pxNewTCB = NULL;
        }
    }
    #endif /* portSTACK_GROWTH */
    if (pxNewTCB != NULL) {
        #if (tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE != 0)
        {
            /* Tasks can be created statically or dynamically, so note this
             * task was created dynamically in case it is later deleted. */
            pxNewTCB->ucStaticallyAllocated = tskDYNAMICALLY_ALLOCATED_STACK_AND_TCB;
        }
        #endif /* tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE */
        prvInitialiseNewTask(pxTaskCode,
                             pcName,
                             (uint32_t)usStackDepth,
                             pvParameters,
                             uxPriority,
                             pxCreatedTask,
                             pxNewTCB,
                             NULL);
        /* 新创建的任务，加入任务就绪队列 */
        prvAddNewTaskToReadyList(pxNewTCB);
        xReturn = pdPASS;
    }
    else
    {
        xReturn = errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY;
    }
    return xReturn;
}

static void prvInitialiseNewTask(TaskFunction_t pxTaskCode,
                                  const char * const pcName,
                                  const uint32_t ulStackDepth,
                                  void * const pvParameters,
                                  UBaseType_t uxPriority,
                                  TaskHandle_t * const pxCreatedTask,
                                  TCB_t * pxNewTCB,
                                  const MemoryRegion_t * const xRegions)
{
    StackType_t * pxTopOfStack;
    UBaseType_t x;

    #if (portUSING_MPU_WRAPPERS == 1)
        /* Should the task be created in privileged mode? */
        BaseType_t xRunPrivileged;

        if ((uxPriority & portPRIVILEGE_BIT) != 0U)
        {
            xRunPrivileged = pdTRUE;
        }
        else
        {
            xRunPrivileged = pdFALSE;
        }
        uxPriority &= ~portPRIVILEGE_BIT;
    #endif /* portUSING_MPU_WRAPPERS == 1 */

    /* Avoid dependency on memset() if it is not required. */
    #if (tskSET_NEW_STACKS_TO_KNOWN_VALUE == 1)
    {
        /* Fill the stack with a known value to assist debugging. */
        (void)memset(pxNewTCB->pxStack, (int)tskSTACK_FILL_BYTE, (size_t) ulStackDepth * sizeof(StackType_t));
    }
    #endif /* tskSET_NEW_STACKS_TO_KNOWN_VALUE */

    /* Calculate the top of stack address.  This depends on whether the stack
     * grows from high memory to low (as per the 80x86) or vice versa.
     * portSTACK_GROWTH is used to make the result positive or negative as required
     * by the port.
     * portSTACK_GROWTH小于0，栈向下生长(高地址往低地址)
     */
    #if (portSTACK_GROWTH < 0)
    {
        /* 设置栈顶的位置(高地址) */
        pxTopOfStack = &(pxNewTCB->pxStack[ulStackDepth - (uint32_t)1]);
        /* 栈地址对齐到portBYTE_ALIGNMENT_MASK */
        pxTopOfStack = (StackType_t *)(((portPOINTER_SIZE_TYPE) pxTopOfStack) & (~((portPOINTER_SIZE_TYPE) portBYTE_ALIGNMENT_MASK)));
        /**
         * Check the alignment of the calculated top of stack is correct.
         * 如果栈地址不对齐，发出assert
         */
        configASSERT((((portPOINTER_SIZE_TYPE)pxTopOfStack & (portPOINTER_SIZE_TYPE)portBYTE_ALIGNMENT_MASK) == 0UL));

        #if (configRECORD_STACK_HIGH_ADDRESS == 1)
        {
            /* Also record the stack's high address, which may assist
             * debugging. */
            pxNewTCB->pxEndOfStack = pxTopOfStack;
        }
        #endif /* configRECORD_STACK_HIGH_ADDRESS */
    }
    #else
    {
        /* 栈向上生长, 栈顶地址就是栈的起始地址 */
        pxTopOfStack = pxNewTCB->pxStack;

        /* Check the alignment of the stack buffer is correct. */
        configASSERT((((portPOINTER_SIZE_TYPE) pxNewTCB->pxStack & (portPOINTER_SIZE_TYPE) portBYTE_ALIGNMENT_MASK) == 0UL));

        /**
         * The other extreme of the stack space is required if stack checking is
         * performed.
         * 计算出栈底的地址
         */
        pxNewTCB->pxEndOfStack = pxNewTCB->pxStack + (ulStackDepth - (uint32_t)1);
    }
    #endif /* portSTACK_GROWTH */

    /* Store the task name in the TCB. */
    if (pcName != NULL) {
        for (x = (UBaseType_t) 0; x < (UBaseType_t) configMAX_TASK_NAME_LEN; x++) {
            /* 保存任务名称 */
            pxNewTCB->pcTaskName[x] = pcName[x];

            /* Don't copy all configMAX_TASK_NAME_LEN if the string is shorter than
             * configMAX_TASK_NAME_LEN characters just in case the memory after the
             * string is not accessible (extremely unlikely). */
            if (pcName[x] == (char) 0x00) {
                break;
            }
        }

        /* Ensure the name string is terminated in the case that the string length
         * was greater or equal to configMAX_TASK_NAME_LEN. */
        pxNewTCB->pcTaskName[configMAX_TASK_NAME_LEN - 1] = '\0';
    }

    /* This is used as an array index so must ensure it's not too large. */
    configASSERT(uxPriority < configMAX_PRIORITIES);

    if (uxPriority >= (UBaseType_t) configMAX_PRIORITIES) {
        uxPriority = (UBaseType_t) configMAX_PRIORITIES - (UBaseType_t)1U;
    }

    pxNewTCB->uxPriority = uxPriority;
    #if (configUSE_MUTEXES == 1)
    {
        pxNewTCB->uxBasePriority = uxPriority;
    }
    #endif /* configUSE_MUTEXES */

    vListInitialiseItem(&(pxNewTCB->xStateListItem));
    vListInitialiseItem(&(pxNewTCB->xEventListItem));

    /* Set the pxNewTCB as a link back from the ListItem_t.  This is so we can get
     * back to  the containing TCB from a generic item in a list. */
    listSET_LIST_ITEM_OWNER(&(pxNewTCB->xStateListItem), pxNewTCB);

    /* Event lists are always in priority order. */
    listSET_LIST_ITEM_VALUE(&(pxNewTCB->xEventListItem), (TickType_t)configMAX_PRIORITIES - (TickType_t)uxPriority);
    listSET_LIST_ITEM_OWNER(&(pxNewTCB->xEventListItem), pxNewTCB);

    #if (portUSING_MPU_WRAPPERS == 1)
    {
        vPortStoreTaskMPUSettings(&(pxNewTCB->xMPUSettings), xRegions, pxNewTCB->pxStack, ulStackDepth);
    }
    #else
    {
        /* Avoid compiler warning about unreferenced parameter. */
        (void) xRegions;
    }
    #endif

    #if ((configUSE_NEWLIB_REENTRANT == 1) || (configUSE_C_RUNTIME_TLS_SUPPORT == 1))
    {
        /* Allocate and initialize memory for the task's TLS Block. */
        configINIT_TLS_BLOCK(pxNewTCB->xTLSBlock);
    }
    #endif

    /* Initialize the TCB stack to look as if the task was already running,
     * but had been interrupted by the scheduler.  The return address is set
     * to the start of the task function. Once the stack has been initialised
     * the top of stack variable is updated. */
    #if (portUSING_MPU_WRAPPERS == 1)
    {
        /* If the port has capability to detect stack overflow,
         * pass the stack end address to the stack initialization
         * function as well. */
        #if (portHAS_STACK_OVERFLOW_CHECKING == 1)
        {
            #if (portSTACK_GROWTH < 0)
            {
                pxNewTCB->pxTopOfStack = pxPortInitialiseStack(pxTopOfStack, pxNewTCB->pxStack, pxTaskCode, pvParameters, xRunPrivileged);
            }
            #else /* portSTACK_GROWTH */
            {
                pxNewTCB->pxTopOfStack = pxPortInitialiseStack(pxTopOfStack, pxNewTCB->pxEndOfStack, pxTaskCode, pvParameters, xRunPrivileged);
            }
            #endif /* portSTACK_GROWTH */
        }
        #else /* portHAS_STACK_OVERFLOW_CHECKING */
        {
            pxNewTCB->pxTopOfStack = pxPortInitialiseStack(pxTopOfStack, pxTaskCode, pvParameters, xRunPrivileged);
        }
        #endif /* portHAS_STACK_OVERFLOW_CHECKING */
    }
    #else /* portUSING_MPU_WRAPPERS */
    {
        /* If the port has capability to detect stack overflow,
         * pass the stack end address to the stack initialization
         * function as well. */
        #if (portHAS_STACK_OVERFLOW_CHECKING == 1)
        {
            #if (portSTACK_GROWTH < 0)
            {
                pxNewTCB->pxTopOfStack = pxPortInitialiseStack(pxTopOfStack, pxNewTCB->pxStack, pxTaskCode, pvParameters);
            }
            #else /* portSTACK_GROWTH */
            {
                pxNewTCB->pxTopOfStack = pxPortInitialiseStack(pxTopOfStack, pxNewTCB->pxEndOfStack, pxTaskCode, pvParameters);
            }
            #endif /* portSTACK_GROWTH */
        }
        #else /* portHAS_STACK_OVERFLOW_CHECKING */
        {
            /* 指向 任务栈中的R11的位置 */
            pxNewTCB->pxTopOfStack = pxPortInitialiseStack(pxTopOfStack, pxTaskCode, pvParameters);
        }
        #endif /* portHAS_STACK_OVERFLOW_CHECKING */
    }
    #endif /* portUSING_MPU_WRAPPERS */

    if (pxCreatedTask != NULL)
    {
        /* Pass the handle out in an anonymous way.  The handle can be used to
         * change the created task's priority, delete the created task, etc.*/
        *pxCreatedTask = (TaskHandle_t) pxNewTCB;
    }

}

static void prvAddNewTaskToReadyList(TCB_t * pxNewTCB)
{
    /* Ensure interrupts don't access the task lists while the lists are being
     * updated. */
    taskENTER_CRITICAL();
    {
        /* 累加系统任务数 */
        uxCurrentNumberOfTasks++;

        /* 系统当前没有任务运行 */
        if (pxCurrentTCB == NULL) {
            /**
             * There are no other tasks, or all the other tasks are in
             * the suspended state - make this the current task.
             * 系统没任务或者所有任务都被挂起了
             */
            pxCurrentTCB = pxNewTCB;
            /* 系统第一次创建任务 */
            if (uxCurrentNumberOfTasks == (UBaseType_t)1) {
                /* This is the first task to be created so do the preliminary
                 * initialisation required.  We will not recover if this call
                 * fails, but we will report the failure. */
                prvInitialiseTaskLists();
            }
        }
        else
        {
            /* If the scheduler is not already running, make this task the
             * current task if it is the highest priority task to be created
             * so far.
             * 任务调度器还没有运行
             */
            if (xSchedulerRunning == pdFALSE) {
                /* 如果新建任务的优先级，大于当前任务的优先级，将新创建的任务设置为当前任务 */
                if (pxCurrentTCB->uxPriority <= pxNewTCB->uxPriority)
                {
                    pxCurrentTCB = pxNewTCB;
                }
            }
        }

        uxTaskNumber++;

        #if (configUSE_TRACE_FACILITY == 1)
        {
            /* Add a counter into the TCB for tracing only. */
            pxNewTCB->uxTCBNumber = uxTaskNumber;
        }
        #endif /* configUSE_TRACE_FACILITY */
        traceTASK_CREATE(pxNewTCB);

        /* 新创建的任务，加入就绪队列 */
        prvAddTaskToReadyList(pxNewTCB);

        portSETUP_TCB(pxNewTCB);
    }
    taskEXIT_CRITICAL();

    /* 调度器已经开始运行, 检查新创建的任务，是否可以抢占，当前正在运行的任务 */
    if (xSchedulerRunning == pdTRUE) {
        /**
         * 新创建的任务优先级高于当前正在运行任务的优先级，触发抢占
         */
        if (pxCurrentTCB->uxPriority < pxNewTCB->uxPriority)
        {
            /**
             * 对于cortex-m系列的arm来说，就是触发PendSVHandler异常
             */
            taskYIELD_IF_USING_PREEMPTION();
        }
    }
}

#if (INCLUDE_vTaskDelete == 1)

/**
 * 删除任务
 * @ xTaskToDelete: 待删除的任务
 */
void vTaskDelete(TaskHandle_t xTaskToDelete)
{
    TCB_t * pxTCB;

    taskENTER_CRITICAL();
    {
        /**
         * If null is passed in here then it is the calling task that is
         * being deleted.
         */
        pxTCB = prvGetTCBFromHandle(xTaskToDelete);
        /**
         * Remove task from the ready/delayed list.
         * 任务从就绪队列删除
         */
        if (uxListRemove(&(pxTCB->xStateListItem)) == (UBaseType_t)0)
        {
            taskRESET_READY_PRIORITY(pxTCB->uxPriority);
        }
        /**
         * Is the task waiting on an event also?
         * 如果待删除任务正在等待事件
         */
        if (listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) != NULL)
        {
            /* 直接从事件链表中删除 */
            (void)uxListRemove(&(pxTCB->xEventListItem));
        }
        /* Increment the uxTaskNumber also so kernel aware debuggers can
         * detect that the task lists need re-generating.  This is done before
         * portPRE_TASK_DELETE_HOOK() as in the Windows port that macro will
         * not return. */
        uxTaskNumber++;
        /* 待删除任务是当前正在运行的任务 */
        if (pxTCB == pxCurrentTCB) {
            /* A task is deleting itself.  This cannot complete within the
             * task itself, as a context switch to another task is required.
             * Place the task in the termination list.  The idle task will
             * check the termination list and free up any memory allocated by
             * the scheduler for the TCB and stack of the deleted task.
             * 加入到待删除任务管理队列
             */
            vListInsertEnd(&xTasksWaitingTermination, &(pxTCB->xStateListItem));
            /* Increment the ucTasksDeleted variable so the idle task knows
             * there is a task that has been deleted and that it should therefore
             * check the xTasksWaitingTermination list. */
            ++uxDeletedTasksWaitingCleanUp;
            /* Call the delete hook before portPRE_TASK_DELETE_HOOK() as
             * portPRE_TASK_DELETE_HOOK() does not return in the Win32 port. */
            traceTASK_DELETE(pxTCB);
            /* The pre-delete hook is primarily for the Windows simulator,
             * in which Windows specific clean up operations are performed,
             * after which it is not possible to yield away from this task -
             * hence xYieldPending is used to latch that a context switch is
             * required. */
            portPRE_TASK_DELETE_HOOK(pxTCB, &xYieldPending);
        }
        else
        {
            --uxCurrentNumberOfTasks;
            traceTASK_DELETE(pxTCB);
            /* Reset the next expected unblock time in case it referred to
             * the task that has just been deleted. */
            prvResetNextTaskUnblockTime();
        }
    }
    taskEXIT_CRITICAL();
    /* If the task is not deleting itself, call prvDeleteTCB from outside of
     * critical section. If a task deletes itself, prvDeleteTCB is called
     * from prvCheckTasksWaitingTermination which is called from Idle task. */
    if (pxTCB != pxCurrentTCB)
    {
        prvDeleteTCB(pxTCB);
    }
    /* Force a reschedule if it is the currently running task that has just
     * been deleted. */
    if (xSchedulerRunning == pdTRUE)
    {
        /* 待删除任务是自己 */
        if (pxTCB == pxCurrentTCB)
        {
            configASSERT(uxSchedulerSuspended == 0);
            /* 多触发一次任务调度 */
            portYIELD_WITHIN_API();
        }
    }
}
#endif

#if (INCLUDE_xTaskDelayUntil == 1)

BaseType_t xTaskDelayUntil(TickType_t * const pxPreviousWakeTime,
                            const TickType_t xTimeIncrement)
{
    TickType_t xTimeToWake;
    BaseType_t xAlreadyYielded, xShouldDelay = pdFALSE;
    configASSERT(pxPreviousWakeTime);
    configASSERT((xTimeIncrement > 0U));
    configASSERT(uxSchedulerSuspended == 0);
    vTaskSuspendAll();
    {
        /* Minor optimisation.  The tick count cannot change in this
         * block. */
        const TickType_t xConstTickCount = xTickCount;
        /* Generate the tick time at which the task wants to wake. */
        xTimeToWake = *pxPreviousWakeTime + xTimeIncrement;
        if (xConstTickCount < *pxPreviousWakeTime)
        {
            /* The tick count has overflowed since this function was
             * lasted called.  In this case the only time we should ever
             * actually delay is if the wake time has also  overflowed,
             * and the wake time is greater than the tick time.  When this
             * is the case it is as if neither time had overflowed. */
            if ((xTimeToWake < *pxPreviousWakeTime) && (xTimeToWake > xConstTickCount))
            {
                xShouldDelay = pdTRUE;
            }
        }
        else
        {
            /* The tick time has not overflowed.  In this case we will
             * delay if either the wake time has overflowed, and/or the
             * tick time is less than the wake time. */
            if ((xTimeToWake < *pxPreviousWakeTime) || (xTimeToWake > xConstTickCount))
            {
                xShouldDelay = pdTRUE;
            }
        }
        /* Update the wake time ready for the next call. */
        *pxPreviousWakeTime = xTimeToWake;
        if (xShouldDelay != pdFALSE)
        {
            traceTASK_DELAY_UNTIL(xTimeToWake);
            /* prvAddCurrentTaskToDelayedList() needs the block time, not
             * the time to wake, so subtract the current tick count. */
            prvAddCurrentTaskToDelayedList(xTimeToWake - xConstTickCount, pdFALSE);
        }
    }
    xAlreadyYielded = xTaskResumeAll();
    /* Force a reschedule if xTaskResumeAll has not already done so, we may
     * have put ourselves to sleep. */
    if (xAlreadyYielded == pdFALSE)
    {
        portYIELD_WITHIN_API();
    }
    return xShouldDelay;
}

#endif /* INCLUDE_xTaskDelayUntil */

#if (INCLUDE_vTaskDelay == 1)

/**
 * 相对延迟
 * @xTicksToDelay: 系统相对节拍数
 */
void vTaskDelay(const TickType_t xTicksToDelay)
{
    BaseType_t xAlreadyYielded = pdFALSE;
    /* A delay time of zero just forces a reschedule. */
    if (xTicksToDelay > (TickType_t)0U)
    {
        configASSERT(uxSchedulerSuspended == 0);
        /* 临时挂起任务调度 */
        vTaskSuspendAll();
        {
            traceTASK_DELAY();
            /* A task that is removed from the event list while the
             * scheduler is suspended will not get placed in the ready
             * list or removed from the blocked list until the scheduler
             * is resumed.
             *
             * This task cannot be in an event list as it is the currently
             * executing task. */
            prvAddCurrentTaskToDelayedList(xTicksToDelay, pdFALSE);
        }
        /* 恢复任务调度 */
        xAlreadyYielded = xTaskResumeAll();
    }
    /**
     * Force a reschedule if xTaskResumeAll has not already done so, we may
     * have put ourselves to sleep.
     * 如果有任务需要被调度，触发任务调度，执行延迟的任务被挂起
     */
    if (xAlreadyYielded == pdFALSE)
    {
        portYIELD_WITHIN_API();
    }
}

#endif

#if ((INCLUDE_eTaskGetState == 1) || (configUSE_TRACE_FACILITY == 1) || (INCLUDE_xTaskAbortDelay == 1))

    eTaskState eTaskGetState(TaskHandle_t xTask)
    {
        eTaskState eReturn;
        List_t const * pxStateList;
        List_t const * pxDelayedList;
        List_t const * pxOverflowedDelayedList;
        const TCB_t * const pxTCB = xTask;

        configASSERT(pxTCB);

        if (pxTCB == pxCurrentTCB)
        {
            /* The task calling this function is querying its own state. */
            eReturn = eRunning;
        }
        else
        {
            taskENTER_CRITICAL();
            {
                pxStateList = listLIST_ITEM_CONTAINER(&(pxTCB->xStateListItem));
                pxDelayedList = pxDelayedTaskList;
                pxOverflowedDelayedList = pxOverflowDelayedTaskList;
            }
            taskEXIT_CRITICAL();

            if ((pxStateList == pxDelayedList) || (pxStateList == pxOverflowedDelayedList))
            {
                /* The task being queried is referenced from one of the Blocked
                 * lists. */
                eReturn = eBlocked;
            }

            #if (INCLUDE_vTaskSuspend == 1)
                else if (pxStateList == &xSuspendedTaskList)
                {
                    /* The task being queried is referenced from the suspended
                     * list.  Is it genuinely suspended or is it blocked
                     * indefinitely? */
                    if (listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) == NULL)
                    {
                        #if (configUSE_TASK_NOTIFICATIONS == 1)
                        {
                            BaseType_t x;

                            /* The task does not appear on the event list item of
                             * and of the RTOS objects, but could still be in the
                             * blocked state if it is waiting on its notification
                             * rather than waiting on an object.  If not, is
                             * suspended. */
                            eReturn = eSuspended;

                            for (x = 0; x < configTASK_NOTIFICATION_ARRAY_ENTRIES; x++)
                            {
                                if (pxTCB->ucNotifyState[x] == taskWAITING_NOTIFICATION)
                                {
                                    eReturn = eBlocked;
                                    break;
                                }
                            }
                        }
                        #else /* if (configUSE_TASK_NOTIFICATIONS == 1) */
                        {
                            eReturn = eSuspended;
                        }
                        #endif /* if (configUSE_TASK_NOTIFICATIONS == 1) */
                    }
                    else
                    {
                        eReturn = eBlocked;
                    }
                }
            #endif /* if (INCLUDE_vTaskSuspend == 1) */

            #if (INCLUDE_vTaskDelete == 1)
                else if ((pxStateList == &xTasksWaitingTermination) || (pxStateList == NULL))
                {
                    /* The task being queried is referenced from the deleted
                     * tasks list, or it is not referenced from any lists at
                     * all. */
                    eReturn = eDeleted;
                }
            #endif

            else /*lint !e525 Negative indentation is intended to make use of pre-processor clearer. */
            {
                /* If the task is not in any other state, it must be in the
                 * Ready (including pending ready) state. */
                eReturn = eReady;
            }
        }

        return eReturn;
    } /*lint !e818 xTask cannot be a pointer to const because it is a typedef. */

#endif /* INCLUDE_eTaskGetState */

#if (INCLUDE_uxTaskPriorityGet == 1)

    UBaseType_t uxTaskPriorityGet(const TaskHandle_t xTask)
    {
        TCB_t const * pxTCB;
        UBaseType_t uxReturn;

        taskENTER_CRITICAL();
        {
            /* If null is passed in here then it is the priority of the task
             * that called uxTaskPriorityGet() that is being queried. */
            pxTCB = prvGetTCBFromHandle(xTask);
            uxReturn = pxTCB->uxPriority;
        }
        taskEXIT_CRITICAL();

        return uxReturn;
    }

#endif

#if (INCLUDE_uxTaskPriorityGet == 1)

    UBaseType_t uxTaskPriorityGetFromISR(const TaskHandle_t xTask)
    {
        TCB_t const * pxTCB;
        UBaseType_t uxReturn, uxSavedInterruptState;

        /* RTOS ports that support interrupt nesting have the concept of a
         * maximum  system call (or maximum API call) interrupt priority.
         * Interrupts that are  above the maximum system call priority are keep
         * permanently enabled, even when the RTOS kernel is in a critical section,
         * but cannot make any calls to FreeRTOS API functions.  If configASSERT()
         * is defined in FreeRTOSConfig.h then
         * portASSERT_IF_INTERRUPT_PRIORITY_INVALID() will result in an assertion
         * failure if a FreeRTOS API function is called from an interrupt that has
         * been assigned a priority above the configured maximum system call
         * priority.  Only FreeRTOS functions that end in FromISR can be called
         * from interrupts  that have been assigned a priority at or (logically)
         * below the maximum system call interrupt priority.  FreeRTOS maintains a
         * separate interrupt safe API to ensure interrupt entry is as fast and as
         * simple as possible.  More information (albeit Cortex-M specific) is
         * provided on the following link:
         * https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
        portASSERT_IF_INTERRUPT_PRIORITY_INVALID();

        uxSavedInterruptState = portSET_INTERRUPT_MASK_FROM_ISR();
        {
            /* If null is passed in here then it is the priority of the calling
             * task that is being queried. */
            pxTCB = prvGetTCBFromHandle(xTask);
            uxReturn = pxTCB->uxPriority;
        }
        portCLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptState);

        return uxReturn;
    }

#endif /* INCLUDE_uxTaskPriorityGet */

#if (INCLUDE_vTaskPrioritySet == 1)

void vTaskPrioritySet(TaskHandle_t xTask, UBaseType_t uxNewPriority)
{
    TCB_t * pxTCB;
    UBaseType_t uxCurrentBasePriority, uxPriorityUsedOnEntry;
    BaseType_t xYieldRequired = pdFALSE;
    configASSERT(uxNewPriority < configMAX_PRIORITIES);
    /* Ensure the new priority is valid. */
    if (uxNewPriority >= (UBaseType_t)configMAX_PRIORITIES)
    {
        uxNewPriority = (UBaseType_t)configMAX_PRIORITIES - (UBaseType_t)1U;
    }
    taskENTER_CRITICAL();
    {
        /* If null is passed in here then it is the priority of the calling
         * task that is being changed. */
        pxTCB = prvGetTCBFromHandle(xTask);
        traceTASK_PRIORITY_SET(pxTCB, uxNewPriority);
        #if (configUSE_MUTEXES == 1)
        {
            uxCurrentBasePriority = pxTCB->uxBasePriority;
        }
        #else
        {
            uxCurrentBasePriority = pxTCB->uxPriority;
        }
        #endif
        if (uxCurrentBasePriority != uxNewPriority)
        {
            /* The priority change may have readied a task of higher
             * priority than the calling task. */
            if (uxNewPriority > uxCurrentBasePriority)
            {
                if (pxTCB != pxCurrentTCB)
                {
                    /* The priority of a task other than the currently
                     * running task is being raised.  Is the priority being
                     * raised above that of the running task? */
                    if (uxNewPriority >= pxCurrentTCB->uxPriority)
                    {
                        xYieldRequired = pdTRUE;
                    }
                }
                else
                {
                    /* The priority of the running task is being raised,
                     * but the running task must already be the highest
                     * priority task able to run so no yield is required. */
                }
            }
            else if (pxTCB == pxCurrentTCB)
            {
                /* Setting the priority of the running task down means
                 * there may now be another task of higher priority that
                 * is ready to execute. */
                xYieldRequired = pdTRUE;
            }
            else
            {
                /* Setting the priority of any other task down does not
                 * require a yield as the running task must be above the
                 * new priority of the task being modified. */
            }
            /* Remember the ready list the task might be referenced from
             * before its uxPriority member is changed so the
             * taskRESET_READY_PRIORITY() macro can function correctly. */
            uxPriorityUsedOnEntry = pxTCB->uxPriority;
            #if (configUSE_MUTEXES == 1)
            {
                /* Only change the priority being used if the task is not
                 * currently using an inherited priority. */
                if (pxTCB->uxBasePriority == pxTCB->uxPriority)
                {
                    pxTCB->uxPriority = uxNewPriority;
                }
                /* The base priority gets set whatever. */
                pxTCB->uxBasePriority = uxNewPriority;
            }
            #else /* if (configUSE_MUTEXES == 1) */
            {
                pxTCB->uxPriority = uxNewPriority;
            }
            #endif /* if (configUSE_MUTEXES == 1) */
            /* Only reset the event list item value if the value is not
             * being used for anything else. */
            if ((listGET_LIST_ITEM_VALUE(&(pxTCB->xEventListItem)) & taskEVENT_LIST_ITEM_VALUE_IN_USE) == 0UL)
            {
                listSET_LIST_ITEM_VALUE(&(pxTCB->xEventListItem), ((TickType_t)configMAX_PRIORITIES - (TickType_t)uxNewPriority));
            }

            /* If the task is in the blocked or suspended list we need do
             * nothing more than change its priority variable. However, if
             * the task is in a ready list it needs to be removed and placed
             * in the list appropriate to its new priority. */
            if (listIS_CONTAINED_WITHIN(&(pxReadyTasksLists[uxPriorityUsedOnEntry]), &(pxTCB->xStateListItem)) != pdFALSE)
            {
                /* The task is currently in its ready list - remove before
                 * adding it to its new ready list.  As we are in a critical
                 * section we can do this even if the scheduler is suspended. */
                if (uxListRemove(&(pxTCB->xStateListItem)) == (UBaseType_t)0)
                {
                    /* It is known that the task is in its ready list so
                     * there is no need to check again and the port level
                     * reset macro can be called directly. */
                    portRESET_READY_PRIORITY(uxPriorityUsedOnEntry, uxTopReadyPriority);
                }
                prvAddTaskToReadyList(pxTCB);
            }
            if (xYieldRequired != pdFALSE)
            {
                taskYIELD_IF_USING_PREEMPTION();
            }
            /* Remove compiler warning about unused variables when the port
             * optimised task selection is not being used. */
            (void) uxPriorityUsedOnEntry;
        }
    }
    taskEXIT_CRITICAL();
}

#endif /* INCLUDE_vTaskPrioritySet */


#if (INCLUDE_vTaskSuspend == 1)

void vTaskSuspend(TaskHandle_t xTaskToSuspend)
{
    TCB_t * pxTCB;
    taskENTER_CRITICAL();
    {
        /* If null is passed in here then it is the running task that is
         * being suspended. */
        pxTCB = prvGetTCBFromHandle(xTaskToSuspend);
        traceTASK_SUSPEND(pxTCB);
        /* Remove task from the ready/delayed list and place in the
         * suspended list. */
        if (uxListRemove(&(pxTCB->xStateListItem)) == (UBaseType_t)0)
        {
            taskRESET_READY_PRIORITY(pxTCB->uxPriority);
        }
        /* Is the task waiting on an event also? */
        if (listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) != NULL)
        {
            (void) uxListRemove(&(pxTCB->xEventListItem));
        }
        vListInsertEnd(&xSuspendedTaskList, &(pxTCB->xStateListItem));
        #if (configUSE_TASK_NOTIFICATIONS == 1)
        {
            BaseType_t x;
            for (x = 0; x < configTASK_NOTIFICATION_ARRAY_ENTRIES; x++)
            {
                if (pxTCB->ucNotifyState[x] == taskWAITING_NOTIFICATION)
                {
                    /* The task was blocked to wait for a notification, but is
                     * now suspended, so no notification was received. */
                    pxTCB->ucNotifyState[x] = taskNOT_WAITING_NOTIFICATION;
                }
            }
        }
        #endif /* if (configUSE_TASK_NOTIFICATIONS == 1) */
    }
    taskEXIT_CRITICAL();
    if (xSchedulerRunning != pdFALSE)
    {
        /* Reset the next expected unblock time in case it referred to the
         * task that is now in the Suspended state. */
        taskENTER_CRITICAL();
        {
            prvResetNextTaskUnblockTime();
        }
        taskEXIT_CRITICAL();
    }
    if (pxTCB == pxCurrentTCB)
    {
        if (xSchedulerRunning != pdFALSE)
        {
            /* The current task has just been suspended. */
            configASSERT(uxSchedulerSuspended == 0);
            portYIELD_WITHIN_API();
        }
        else
        {
            /* The scheduler is not running, but the task that was pointed
             * to by pxCurrentTCB has just been suspended and pxCurrentTCB
             * must be adjusted to point to a different task. */
            if (listCURRENT_LIST_LENGTH(&xSuspendedTaskList) == uxCurrentNumberOfTasks)
            {
                /* No other tasks are ready, so set pxCurrentTCB back to
                 * NULL so when the next task is created pxCurrentTCB will
                 * be set to point to it no matter what its relative priority
                 * is. */
                pxCurrentTCB = NULL;
            }
            else
            {
                vTaskSwitchContext();
            }
        }
    }
}

static BaseType_t prvTaskIsTaskSuspended(const TaskHandle_t xTask)
{
    BaseType_t xReturn = pdFALSE;
    const TCB_t * const pxTCB = xTask;
    /* Accesses xPendingReadyList so must be called from a critical
     * section. */
    /* It does not make sense to check if the calling task is suspended. */
    configASSERT(xTask);
    /* Is the task being resumed actually in the suspended list? */
    if (listIS_CONTAINED_WITHIN(&xSuspendedTaskList, &(pxTCB->xStateListItem)) != pdFALSE)
    {
        /* Has the task already been resumed from within an ISR? */
        if (listIS_CONTAINED_WITHIN(&xPendingReadyList, &(pxTCB->xEventListItem)) == pdFALSE)
        {
            /* Is it in the suspended list because it is in the Suspended
             * state, or because is is blocked with no timeout? */
            if (listIS_CONTAINED_WITHIN(NULL, &(pxTCB->xEventListItem)) != pdFALSE)
            {
                xReturn = pdTRUE;
            }
        }
    }

    return xReturn;
}

void vTaskResume(TaskHandle_t xTaskToResume)
{
    TCB_t * const pxTCB = xTaskToResume;
    /* It does not make sense to resume the calling task. */
    configASSERT(xTaskToResume);
    /* The parameter cannot be NULL as it is impossible to resume the
     * currently executing task. */
    if ((pxTCB != pxCurrentTCB) && (pxTCB != NULL))
    {
        taskENTER_CRITICAL();
        {
            if (prvTaskIsTaskSuspended(pxTCB) != pdFALSE)
            {
                traceTASK_RESUME(pxTCB);
                /* The ready list can be accessed even if the scheduler is
                 * suspended because this is inside a critical section. */
                (void) uxListRemove(&(pxTCB->xStateListItem));
                prvAddTaskToReadyList(pxTCB);
                /* A higher priority task may have just been resumed. */
                if (pxTCB->uxPriority >= pxCurrentTCB->uxPriority)
                {
                    /* This yield may not cause the task just resumed to run,
                     * but will leave the lists in the correct state for the
                     * next yield. */
                    taskYIELD_IF_USING_PREEMPTION();
                }
            }
        }
        taskEXIT_CRITICAL();
    }
}

#endif /* INCLUDE_vTaskSuspend */


#if ((INCLUDE_xTaskResumeFromISR == 1) && (INCLUDE_vTaskSuspend == 1))

BaseType_t xTaskResumeFromISR(TaskHandle_t xTaskToResume)
{
    BaseType_t xYieldRequired = pdFALSE;
    TCB_t * const pxTCB = xTaskToResume;
    UBaseType_t uxSavedInterruptStatus;
    configASSERT(xTaskToResume);
    /* RTOS ports that support interrupt nesting have the concept of a
     * maximum  system call (or maximum API call) interrupt priority.
     * Interrupts that are  above the maximum system call priority are keep
     * permanently enabled, even when the RTOS kernel is in a critical section,
     * but cannot make any calls to FreeRTOS API functions.  If configASSERT()
     * is defined in FreeRTOSConfig.h then
     * portASSERT_IF_INTERRUPT_PRIORITY_INVALID() will result in an assertion
     * failure if a FreeRTOS API function is called from an interrupt that has
     * been assigned a priority above the configured maximum system call
     * priority.  Only FreeRTOS functions that end in FromISR can be called
     * from interrupts  that have been assigned a priority at or (logically)
     * below the maximum system call interrupt priority.  FreeRTOS maintains a
     * separate interrupt safe API to ensure interrupt entry is as fast and as
     * simple as possible.  More information (albeit Cortex-M specific) is
     * provided on the following link:
     * https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
    portASSERT_IF_INTERRUPT_PRIORITY_INVALID();
    uxSavedInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
    {
        if (prvTaskIsTaskSuspended(pxTCB) != pdFALSE)
        {
            traceTASK_RESUME_FROM_ISR(pxTCB);
            /* Check the ready lists can be accessed. */
            if (uxSchedulerSuspended == (UBaseType_t)pdFALSE)
            {
                /* Ready lists can be accessed so move the task from the
                 * suspended list to the ready list directly. */
                if (pxTCB->uxPriority >= pxCurrentTCB->uxPriority)
                {
                    xYieldRequired = pdTRUE;
                    /* Mark that a yield is pending in case the user is not
                     * using the return value to initiate a context switch
                     * from the ISR using portYIELD_FROM_ISR. */
                    xYieldPending = pdTRUE;
                }
                (void)uxListRemove(&(pxTCB->xStateListItem));
                prvAddTaskToReadyList(pxTCB);
            }
            else
            {
                /* The delayed or ready lists cannot be accessed so the task
                 * is held in the pending ready list until the scheduler is
                 * unsuspended. */
                vListInsertEnd(&(xPendingReadyList), &(pxTCB->xEventListItem));
            }
        }
    }
    portCLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptStatus);
    return xYieldRequired;
}

#endif /* ((INCLUDE_xTaskResumeFromISR == 1) && (INCLUDE_vTaskSuspend == 1)) */

void vTaskStartScheduler(void)
{
    BaseType_t xReturn;

    /**
     * 创建系统空闲任务.
     */
    xReturn = xTaskCreate(prvIdleTask,
                               configIDLE_TASK_NAME,
                               configMINIMAL_STACK_SIZE,
                               (void *) NULL,
                               portPRIVILEGE_BIT,       /* 任务优先级最低 */
                               &xIdleTaskHandle);



    #if (configUSE_TIMERS == 1)
    {
        if (xReturn == pdPASS)
        {
            /* 创建软件定时器处理任务 */
            xReturn = xTimerCreateTimerTask();
        }
    }
    #endif

    if (xReturn == pdPASS)
    {
        /* Interrupts are turned off here, to ensure a tick does not occur
         * before or during the call to xPortStartScheduler().  The stacks of
         * the created tasks contain a status word with interrupts switched on
         * so interrupts will automatically get re-enabled when the first task
         * starts to run. */
        portDISABLE_INTERRUPTS();

        #if ((configUSE_NEWLIB_REENTRANT == 1) || (configUSE_C_RUNTIME_TLS_SUPPORT == 1))
        {
            /* Switch C-Runtime's TLS Block to point to the TLS
             * block specific to the task that will run first. */
            configSET_TLS_BLOCK(pxCurrentTCB->xTLSBlock);
        }
        #endif

        xNextTaskUnblockTime = portMAX_DELAY;
        /* 调度器开始运行 */
        xSchedulerRunning = pdTRUE;
        /* 初始化系统tick值 */
        xTickCount = (TickType_t) configINITIAL_TICK_COUNT;

        /* If configGENERATE_RUN_TIME_STATS is defined then the following
         * macro must be defined to configure the timer/counter used to generate
         * the run time counter time base.   NOTE:  If configGENERATE_RUN_TIME_STATS
         * is set to 0 and the following line fails to build then ensure you do not
         * have portCONFIGURE_TIMER_FOR_RUN_TIME_STATS() defined in your
         * FreeRTOSConfig.h file. */
        portCONFIGURE_TIMER_FOR_RUN_TIME_STATS();

        traceTASK_SWITCHED_IN();

        /**
         * Setting up the timer tick is hardware specific and thus in the
         * portable interface.
         * 初始化system tick定时器
         */
        xPortStartScheduler();

        /* In most cases, xPortStartScheduler() will not return. If it
         * returns pdTRUE then there was not enough heap memory available
         * to create either the Idle or the Timer task. If it returned
         * pdFALSE, then the application called xTaskEndScheduler().
         * Most ports don't implement xTaskEndScheduler() as there is
         * nothing to return to. */
    }
    else
    {
        /* This line will only be reached if the kernel could not be started,
         * because there was not enough FreeRTOS heap to create the idle task
         * or the timer task. */
        configASSERT(xReturn != errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY);
    }

    /* Prevent compiler warnings if INCLUDE_xTaskGetIdleTaskHandle is set to 0,
     * meaning xIdleTaskHandle is not used anywhere else. */
    (void) xIdleTaskHandle;

    /* OpenOCD makes use of uxTopUsedPriority for thread debugging. Prevent uxTopUsedPriority
     * from getting optimized out as it is no longer used by the kernel. */
    (void) uxTopUsedPriority;
}


void vTaskEndScheduler(void)
{
    /* Stop the scheduler interrupts and call the portable scheduler end
     * routine so the original ISRs can be restored if necessary.  The port
     * layer must ensure interrupts enable  bit is left in the correct state. */
    portDISABLE_INTERRUPTS();
    xSchedulerRunning = pdFALSE;
    vPortEndScheduler();
}

/**
 * 挂起调度器
 */
void vTaskSuspendAll(void)
{
    /* A critical section is not required as the variable is of type
     * BaseType_t.  Please read Richard Barry's reply in the following link to a
     * post in the FreeRTOS support forum before reporting this as a bug! -
     * https://goo.gl/wu4acr */

    /* portSOFTWARE_BARRIER() is only implemented for emulated/simulated ports that
     * do not otherwise exhibit real time behaviour. */
    portSOFTWARE_BARRIER();

    /* The scheduler is suspended if uxSchedulerSuspended is non-zero.  An increment
     * is used to allow calls to vTaskSuspendAll() to nest. */
    ++uxSchedulerSuspended;

    /* Enforces ordering for ports and optimised compilers that may otherwise place
     * the above increment elsewhere. */
    portMEMORY_BARRIER();
}

#if (configUSE_TICKLESS_IDLE != 0)

/* 计算系统进入低功耗模式的时长 */
static TickType_t prvGetExpectedIdleTime(void)
{
    TickType_t xReturn;
    UBaseType_t uxHigherPriorityReadyTasks = pdFALSE;
    /* uxHigherPriorityReadyTasks takes care of the case where
     * configUSE_PREEMPTION is 0, so there may be tasks above the idle priority
     * task that are in the Ready state, even though the idle task is
     * running. */
    #if (configUSE_PORT_OPTIMISED_TASK_SELECTION == 0)
    {
        if (uxTopReadyPriority > tskIDLE_PRIORITY)
        {
            uxHigherPriorityReadyTasks = pdTRUE;
        }
    }
    #else
    {
        const UBaseType_t uxLeastSignificantBit = (UBaseType_t) 0x01;
        /* When port optimised task selection is used the uxTopReadyPriority
         * variable is used as a bit map.  If bits other than the least
         * significant bit are set then there are tasks that have a priority
         * above the idle priority that are in the Ready state.  This takes
         * care of the case where the co-operative scheduler is in use. */
        if (uxTopReadyPriority > uxLeastSignificantBit)
        {
            uxHigherPriorityReadyTasks = pdTRUE;
        }
    }
    #endif

    /* 有其他任务在运行，则不能进入低功耗 */
    if (pxCurrentTCB->uxPriority > tskIDLE_PRIORITY)
    {
        xReturn = 0;
    }
    else if (listCURRENT_LIST_LENGTH(&(pxReadyTasksLists[tskIDLE_PRIORITY])) > 1)
    {
        /* There are other idle priority tasks in the ready state.  If
         * time slicing is used then the very next tick interrupt must be
         * processed. */
        xReturn = 0;
    }
    else if (uxHigherPriorityReadyTasks != pdFALSE)
    {
        /* There are tasks in the Ready state that have a priority above the
         * idle priority.  This path can only be reached if
         * configUSE_PREEMPTION is 0. */
        xReturn = 0;
    }
    else
    {
        /* 当系统只有空闲任务时，计算出系统可以进入低功耗模式的时长 */
        xReturn = xNextTaskUnblockTime - xTickCount;
    }
    return xReturn;
}

#endif

/**
 * 恢复调度器的运行
 */
BaseType_t xTaskResumeAll(void)
{
    TCB_t * pxTCB = NULL;
    BaseType_t xAlreadyYielded = pdFALSE;

    /* If uxSchedulerSuspended is zero then this function does not match a
     * previous call to vTaskSuspendAll(). */
    configASSERT(uxSchedulerSuspended);

    /* It is possible that an ISR caused a task to be removed from an event
     * list while the scheduler was suspended.  If this was the case then the
     * removed task will have been added to the xPendingReadyList.  Once the
     * scheduler has been resumed it is safe to move all the pending ready
     * tasks from this list into their appropriate ready list. */
    taskENTER_CRITICAL();
    {
        --uxSchedulerSuspended;

        /* 恢复调度器的执行 */
        if (uxSchedulerSuspended == (UBaseType_t)pdFALSE)
        {
            if (uxCurrentNumberOfTasks > (UBaseType_t)0U)
            {
                /**
                 * Move any readied tasks from the pending list into the
                 * appropriate ready list.
                 * 等待调度任务队列不为空
                 */
                while (listLIST_IS_EMPTY(&xPendingReadyList) == pdFALSE)
                {
                    /* 选择优先级最高的任务 */
                    pxTCB = listGET_OWNER_OF_HEAD_ENTRY((&xPendingReadyList));
                    listREMOVE_ITEM(&(pxTCB->xEventListItem));
                    portMEMORY_BARRIER();
                    listREMOVE_ITEM(&(pxTCB->xStateListItem));
                    /* 加入到就绪队列 */
                    prvAddTaskToReadyList(pxTCB);

                    /**
                     * If the moved task has a priority higher than or equal to
                     * the current task then a yield must be performed.
                     * pxTCB的优先级大于当前正在运行任务的优先级，当前运行任务可以
                     * 被抢占
                     */
                    if (pxTCB->uxPriority >= pxCurrentTCB->uxPriority)
                    {
                        xYieldPending = pdTRUE;
                    }
                }

                if (pxTCB != NULL)
                {
                    /* A task was unblocked while the scheduler was suspended,
                     * which may have prevented the next unblock time from being
                     * re-calculated, in which case re-calculate it now.  Mainly
                     * important for low power tickless implementations, where
                     * this can prevent an unnecessary exit from low power
                     * state. */
                    prvResetNextTaskUnblockTime();
                }

                /**
                 * If any ticks occurred while the scheduler was suspended then
                 * they should be processed now.  This ensures the tick count does
                 * not  slip, and that any delayed tasks are resumed at the correct
                 * time.
                 * 系统调度器被挂起后，产生时钟中断，会累计xPendedTicks的值,其实就是累计
                 * 错过调度的次数
                 */
                {
                    TickType_t xPendedCounts = xPendedTicks;

                    /* 处理由于调度器被挂起后，错过的调度次数 */
                    if (xPendedCounts > (TickType_t)0U)
                    {
                        do
                        {
                            if (xTaskIncrementTick() == pdTRUE)
                            {
                                xYieldPending = pdTRUE;
                            }
                            --xPendedCounts;
                        } while (xPendedCounts > (TickType_t)0U);

                        xPendedTicks = 0;
                    }
                }

                /* 任务需要调度 */
                if (xYieldPending == pdTRUE)
                {
                    /* 开启抢占的情况下，当前任务可以被抢占 */
                    #if (configUSE_PREEMPTION != 0)
                    {
                        xAlreadyYielded = pdTRUE;
                    }
                    #endif
                    taskYIELD_IF_USING_PREEMPTION();
                }
            }
        }
    }
    taskEXIT_CRITICAL();

    return xAlreadyYielded;
}

TickType_t xTaskGetTickCount(void)
{
    TickType_t xTicks;

    /* Critical section required if running on a 16 bit processor. */
    portTICK_TYPE_ENTER_CRITICAL();
    {
        xTicks = xTickCount;
    }
    portTICK_TYPE_EXIT_CRITICAL();

    return xTicks;
}

TickType_t xTaskGetTickCountFromISR(void)
{
    TickType_t xReturn;
    UBaseType_t uxSavedInterruptStatus;

    /* RTOS ports that support interrupt nesting have the concept of a maximum
     * system call (or maximum API call) interrupt priority.  Interrupts that are
     * above the maximum system call priority are kept permanently enabled, even
     * when the RTOS kernel is in a critical section, but cannot make any calls to
     * FreeRTOS API functions.  If configASSERT() is defined in FreeRTOSConfig.h
     * then portASSERT_IF_INTERRUPT_PRIORITY_INVALID() will result in an assertion
     * failure if a FreeRTOS API function is called from an interrupt that has been
     * assigned a priority above the configured maximum system call priority.
     * Only FreeRTOS functions that end in FromISR can be called from interrupts
     * that have been assigned a priority at or (logically) below the maximum
     * system call  interrupt priority.  FreeRTOS maintains a separate interrupt
     * safe API to ensure interrupt entry is as fast and as simple as possible.
     * More information (albeit Cortex-M specific) is provided on the following
     * link: https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
    portASSERT_IF_INTERRUPT_PRIORITY_INVALID();

    uxSavedInterruptStatus = portTICK_TYPE_SET_INTERRUPT_MASK_FROM_ISR();
    {
        xReturn = xTickCount;
    }
    portTICK_TYPE_CLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptStatus);

    return xReturn;
}


UBaseType_t uxTaskGetNumberOfTasks(void)
{
    /* A critical section is not required because the variables are of type
     * BaseType_t. */
    return uxCurrentNumberOfTasks;
}


char *pcTaskGetName(TaskHandle_t xTaskToQuery)
{
    TCB_t * pxTCB;

    /* If null is passed in here then the name of the calling task is being
     * queried. */
    pxTCB = prvGetTCBFromHandle(xTaskToQuery);
    configASSERT(pxTCB);
    return &(pxTCB->pcTaskName[0]);
}


#if (INCLUDE_xTaskGetHandle == 1)

static TCB_t *prvSearchForNameWithinSingleList(List_t * pxList, const char pcNameToQuery[])
{
    TCB_t * pxNextTCB;
    TCB_t * pxFirstTCB;
    TCB_t * pxReturn = NULL;
    UBaseType_t x;
    char cNextChar;
    BaseType_t xBreakLoop;
    /* This function is called with the scheduler suspended. */
    if (listCURRENT_LIST_LENGTH(pxList) > (UBaseType_t)0)
    {
        listGET_OWNER_OF_NEXT_ENTRY(pxFirstTCB, pxList);
        do
        {
            listGET_OWNER_OF_NEXT_ENTRY(pxNextTCB, pxList);
            /* Check each character in the name looking for a match or
             * mismatch. */
            xBreakLoop = pdFALSE;
            for (x = (UBaseType_t) 0; x < (UBaseType_t) configMAX_TASK_NAME_LEN; x++)
            {
                cNextChar = pxNextTCB->pcTaskName[x];
                if (cNextChar != pcNameToQuery[x])
                {
                    /* Characters didn't match. */
                    xBreakLoop = pdTRUE;
                }
                else if (cNextChar == (char)0x00)
                {
                    /* Both strings terminated, a match must have been
                     * found. */
                    pxReturn = pxNextTCB;
                    xBreakLoop = pdTRUE;
                }

                if (xBreakLoop != pdFALSE)
                {
                    break;
                }
            }
            if (pxReturn != NULL)
            {
                /* The handle has been found. */
                break;
            }
        } while (pxNextTCB != pxFirstTCB);
    }
    return pxReturn;
}

#endif /* INCLUDE_xTaskGetHandle */

#if (INCLUDE_xTaskGetHandle == 1)

TaskHandle_t xTaskGetHandle(const char * pcNameToQuery)
{
    UBaseType_t uxQueue = configMAX_PRIORITIES;
    TCB_t * pxTCB;
    /* Task names will be truncated to configMAX_TASK_NAME_LEN - 1 bytes. */
    configASSERT(strlen(pcNameToQuery) < configMAX_TASK_NAME_LEN);
    vTaskSuspendAll();
    {
        /* Search the ready lists. */
        do
        {
            uxQueue--;
            pxTCB = prvSearchForNameWithinSingleList((List_t *) &(pxReadyTasksLists[uxQueue]), pcNameToQuery);
            if (pxTCB != NULL)
            {
                /* Found the handle. */
                break;
            }
        } while (uxQueue > (UBaseType_t)tskIDLE_PRIORITY);
        /* Search the delayed lists. */
        if (pxTCB == NULL)
        {
            pxTCB = prvSearchForNameWithinSingleList((List_t *) pxDelayedTaskList, pcNameToQuery);
        }
        if (pxTCB == NULL)
        {
            pxTCB = prvSearchForNameWithinSingleList((List_t *) pxOverflowDelayedTaskList, pcNameToQuery);
        }
        #if (INCLUDE_vTaskSuspend == 1)
        {
            if (pxTCB == NULL)
            {
                /* Search the suspended list. */
                pxTCB = prvSearchForNameWithinSingleList(&xSuspendedTaskList, pcNameToQuery);
            }
        }
        #endif
        #if (INCLUDE_vTaskDelete == 1)
        {
            if (pxTCB == NULL)
            {
                /* Search the deleted list. */
                pxTCB = prvSearchForNameWithinSingleList(&xTasksWaitingTermination, pcNameToQuery);
            }
        }
        #endif
    }
    (void) xTaskResumeAll();
    return pxTCB;
}

#endif /* INCLUDE_xTaskGetHandle */


#if (configUSE_TRACE_FACILITY == 1)

    UBaseType_t uxTaskGetSystemState(TaskStatus_t * const pxTaskStatusArray,
                                      const UBaseType_t uxArraySize,
                                      configRUN_TIME_COUNTER_TYPE * const pulTotalRunTime)
    {
        UBaseType_t uxTask = 0, uxQueue = configMAX_PRIORITIES;

        vTaskSuspendAll();
        {
            /* Is there a space in the array for each task in the system? */
            if (uxArraySize >= uxCurrentNumberOfTasks)
            {
                /* Fill in an TaskStatus_t structure with information on each
                 * task in the Ready state. */
                do
                {
                    uxQueue--;
                    uxTask += prvListTasksWithinSingleList(&(pxTaskStatusArray[uxTask]), &(pxReadyTasksLists[uxQueue]), eReady);
                } while (uxQueue > (UBaseType_t) tskIDLE_PRIORITY); /*lint !e961 MISRA exception as the casts are only redundant for some ports. */

                /* Fill in an TaskStatus_t structure with information on each
                 * task in the Blocked state. */
                uxTask += prvListTasksWithinSingleList(&(pxTaskStatusArray[uxTask]), (List_t *) pxDelayedTaskList, eBlocked);
                uxTask += prvListTasksWithinSingleList(&(pxTaskStatusArray[uxTask]), (List_t *) pxOverflowDelayedTaskList, eBlocked);

                #if (INCLUDE_vTaskDelete == 1)
                {
                    /* Fill in an TaskStatus_t structure with information on
                     * each task that has been deleted but not yet cleaned up. */
                    uxTask += prvListTasksWithinSingleList(&(pxTaskStatusArray[uxTask]), &xTasksWaitingTermination, eDeleted);
                }
                #endif

                #if (INCLUDE_vTaskSuspend == 1)
                {
                    /* Fill in an TaskStatus_t structure with information on
                     * each task in the Suspended state. */
                    uxTask += prvListTasksWithinSingleList(&(pxTaskStatusArray[uxTask]), &xSuspendedTaskList, eSuspended);
                }
                #endif

                #if (configGENERATE_RUN_TIME_STATS == 1)
                {
                    if (pulTotalRunTime != NULL)
                    {
                        #ifdef portALT_GET_RUN_TIME_COUNTER_VALUE
                            portALT_GET_RUN_TIME_COUNTER_VALUE((*pulTotalRunTime));
                        #else
                            *pulTotalRunTime = portGET_RUN_TIME_COUNTER_VALUE();
                        #endif
                    }
                }
                #else /* if (configGENERATE_RUN_TIME_STATS == 1) */
                {
                    if (pulTotalRunTime != NULL)
                    {
                        *pulTotalRunTime = 0;
                    }
                }
                #endif /* if (configGENERATE_RUN_TIME_STATS == 1) */
            }
        }
        (void) xTaskResumeAll();

        return uxTask;
    }

#endif /* configUSE_TRACE_FACILITY */


#if (INCLUDE_xTaskGetIdleTaskHandle == 1)

TaskHandle_t xTaskGetIdleTaskHandle(void)
{
    /* If xTaskGetIdleTaskHandle() is called before the scheduler has been
     * started, then xIdleTaskHandle will be NULL. */
    configASSERT((xIdleTaskHandle != NULL));
    return xIdleTaskHandle;
}

#endif


#if (configUSE_TICKLESS_IDLE != 0)

void vTaskStepTick(TickType_t xTicksToJump)
{
    /* Correct the tick count value after a period during which the tick
     * was suppressed.  Note this does *not* call the tick hook function for
     * each stepped tick. */
    configASSERT((xTickCount + xTicksToJump) <= xNextTaskUnblockTime);
    if ((xTickCount + xTicksToJump) == xNextTaskUnblockTime)
    {
        /* Arrange for xTickCount to reach xNextTaskUnblockTime in
         * xTaskIncrementTick() when the scheduler resumes.  This ensures
         * that any delayed tasks are resumed at the correct time. */
        configASSERT(uxSchedulerSuspended);
        configASSERT(xTicksToJump != (TickType_t)0);
        /* Prevent the tick interrupt modifying xPendedTicks simultaneously. */
        taskENTER_CRITICAL();
        {
            xPendedTicks++;
        }
        taskEXIT_CRITICAL();
        xTicksToJump--;
    }
    xTickCount += xTicksToJump;
    traceINCREASE_TICK_COUNT(xTicksToJump);
}

#endif


BaseType_t xTaskCatchUpTicks(TickType_t xTicksToCatchUp)
{
    BaseType_t xYieldOccurred;

    /* Must not be called with the scheduler suspended as the implementation
     * relies on xPendedTicks being wound down to 0 in xTaskResumeAll(). */
    configASSERT(uxSchedulerSuspended == 0);

    /* Use xPendedTicks to mimic xTicksToCatchUp number of ticks occurring when
     * the scheduler is suspended so the ticks are executed in xTaskResumeAll(). */
    vTaskSuspendAll();

    /* Prevent the tick interrupt modifying xPendedTicks simultaneously. */
    taskENTER_CRITICAL();
    {
        xPendedTicks += xTicksToCatchUp;
    }
    taskEXIT_CRITICAL();
    xYieldOccurred = xTaskResumeAll();

    return xYieldOccurred;
}

#if (INCLUDE_xTaskAbortDelay == 1)

BaseType_t xTaskAbortDelay(TaskHandle_t xTask)
{
    TCB_t * pxTCB = xTask;
    BaseType_t xReturn;
    configASSERT(pxTCB);
    vTaskSuspendAll();
    {
        /* A task can only be prematurely removed from the Blocked state if
         * it is actually in the Blocked state. */
        if (eTaskGetState(xTask) == eBlocked)
        {
            xReturn = pdPASS;
            /* Remove the reference to the task from the blocked list.  An
             * interrupt won't touch the xStateListItem because the
             * scheduler is suspended. */
            (void) uxListRemove(&(pxTCB->xStateListItem));
            /* Is the task waiting on an event also?  If so remove it from
             * the event list too.  Interrupts can touch the event list item,
             * even though the scheduler is suspended, so a critical section
             * is used. */
            taskENTER_CRITICAL();
            {
                if (listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) != NULL)
                {
                    (void) uxListRemove(&(pxTCB->xEventListItem));
                    /* This lets the task know it was forcibly removed from the
                     * blocked state so it should not re-evaluate its block time and
                     * then block again. */
                    pxTCB->ucDelayAborted = pdTRUE;
                }
            }
            taskEXIT_CRITICAL();
            /* Place the unblocked task into the appropriate ready list. */
            prvAddTaskToReadyList(pxTCB);
            /* A task being unblocked cannot cause an immediate context
             * switch if preemption is turned off. */
            #if (configUSE_PREEMPTION == 1)
            {
                /* Preemption is on, but a context switch should only be
                 * performed if the unblocked task has a priority that is
                 * higher than the currently executing task. */
                if (pxTCB->uxPriority > pxCurrentTCB->uxPriority)
                {
                    /* Pend the yield to be performed when the scheduler
                     * is unsuspended. */
                    xYieldPending = pdTRUE;
                }
            }
            #endif /* configUSE_PREEMPTION */
        }
        else
        {
            xReturn = pdFAIL;
        }
    }
    (void) xTaskResumeAll();
    return xReturn;
}

#endif /* INCLUDE_xTaskAbortDelay */


BaseType_t xTaskIncrementTick(void)
{
    TCB_t * pxTCB;
    TickType_t xItemValue;
    BaseType_t xSwitchRequired = pdFALSE;

    /**
     * Called by the portable layer each time a tick interrupt occurs.
     * Increments the tick then checks to see if the new tick value will cause any
     * tasks to be unblocked.
     */
    traceTASK_INCREMENT_TICK(xTickCount);

    /* 调度器如果没有被挂起 */
    if (uxSchedulerSuspended != (UBaseType_t)pdTRUE) {
        /*
         * Minor optimisation.  The tick count cannot change in this
         * block.
         * 累加系统时钟数
         */
        const TickType_t xConstTickCount = xTickCount + (TickType_t)1;

        /* Increment the RTOS tick, switching the delayed and overflowed
         * delayed lists if it wraps to 0. */
        xTickCount = xConstTickCount;

        /* 系统时钟计数器发生溢出 */
        if (xConstTickCount == (TickType_t)0U)
        {
            taskSWITCH_DELAYED_LISTS();
        }

        /* See if this tick has made a timeout expire.  Tasks are stored in
         * the  queue in the order of their wake time - meaning once one task
         * has been found whose block time has not expired there is no need to
         * look any further down the list.
         * 遇见下一个任务超时的时间点
         */
        if (xConstTickCount >= xNextTaskUnblockTime) {
            for (; ;)
            {
                /* 延迟队列为空 */
                if (listLIST_IS_EMPTY(pxDelayedTaskList) != pdFALSE)
                {
                    /* The delayed list is empty.  Set xNextTaskUnblockTime
                     * to the maximum possible value so it is extremely
                     * unlikely that the
                     * if (xTickCount >= xNextTaskUnblockTime) test will pass
                     * next time through.
                     * 设置下一个任务超时的时间为无限大
                     */
                    xNextTaskUnblockTime = portMAX_DELAY;
                    break;
                }
                else
                {
                    /* The delayed list is not empty, get the value of the
                     * item at the head of the delayed list.  This is the time
                     * at which the task at the head of the delayed list must
                     * be removed from the Blocked state.
                     * 链表头部的任务，超时时间值是最小的
                     */
                    pxTCB = listGET_OWNER_OF_HEAD_ENTRY(pxDelayedTaskList);
                    /* 获取任务的超时时间值 */
                    xItemValue = listGET_LIST_ITEM_VALUE(&(pxTCB->xStateListItem));

                    /* 没有超时 */
                    if (xConstTickCount < xItemValue)
                    {
                        /* It is not time to unblock this item yet, but the
                         * item value is the time at which the task at the head
                         * of the blocked list must be removed from the Blocked
                         * state -  so record the item value in
                         * xNextTaskUnblockTime. */
                        xNextTaskUnblockTime = xItemValue;
                        break;
                    }

                    /**
                     * It is time to remove the item from the Blocked state.
                     * 任务从延迟队列中删除
                     */
                    listREMOVE_ITEM(&(pxTCB->xStateListItem));

                    /* Is the task waiting on an event also?  If so remove
                     * it from the event list. */
                    if (listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) != NULL)
                    {
                        listREMOVE_ITEM(&(pxTCB->xEventListItem));
                    }

                    /**
                     * Place the unblocked task into the appropriate ready
                     * list.
                     * 任务加入到就绪队列
                     */
                    prvAddTaskToReadyList(pxTCB);

                    /* A task being unblocked cannot cause an immediate
                     * context switch if preemption is turned off. */
                    #if (configUSE_PREEMPTION == 1)
                    {
                        /* Preemption is on, but a context switch should
                         * only be performed if the unblocked task's
                         * priority is higher than the currently executing
                         * task.
                         * The case of equal priority tasks sharing
                         * processing time (which happens when both
                         * preemption and time slicing are on) is
                         * handled below.
                         * 当前任务可以被抢占
                         */
                        if (pxTCB->uxPriority > pxCurrentTCB->uxPriority)
                        {
                            xSwitchRequired = pdTRUE;
                        }
                    }
                    #endif
                }
            }
        }

        /**
         * Tasks of equal priority to the currently running task will share
         * processing time (time slice) if preemption is on, and the application
         * writer has not explicitly turned time slicing off.
         * 开启抢占情况下，相同优先级的任务，分时间片轮转
         */
        #if ((configUSE_PREEMPTION == 1) && (configUSE_TIME_SLICING == 1))
        {
            /* 存在与pxCurrentTCB相同优先级的待运行任务 */
            if (listCURRENT_LIST_LENGTH(&(pxReadyTasksLists[pxCurrentTCB->uxPriority])) > (UBaseType_t)1)
            {
                xSwitchRequired = pdTRUE;
            }
        }
        #endif

        #if (configUSE_TICK_HOOK == 1)
        {
            /* Guard against the tick hook being called when the pended tick
             * count is being unwound (when the scheduler is being unlocked). */
            if (xPendedTicks == (TickType_t)0)
            {
                vApplicationTickHook();
            }
        }
        #endif

        /* 开启抢占情况下 */
        #if (configUSE_PREEMPTION == 1)
        {
            /* 存在高优先级的任务，触发抢占 */
            if (xYieldPending != pdFALSE)
            {
                xSwitchRequired = pdTRUE;
            }
        }
        #endif /* configUSE_PREEMPTION */
    } else { /* 调度器处于挂起状态 */

        ++xPendedTicks;

        /* The tick hook gets called at regular intervals, even if the
         * scheduler is locked. */
        #if (configUSE_TICK_HOOK == 1)
        {
            vApplicationTickHook();
        }
        #endif
    }

    return xSwitchRequired;
}

#if (configUSE_APPLICATION_TASK_TAG == 1)

    void vTaskSetApplicationTaskTag(TaskHandle_t xTask,
                                     TaskHookFunction_t pxHookFunction)
    {
        TCB_t * xTCB;

        /* If xTask is NULL then it is the task hook of the calling task that is
         * getting set. */
        if (xTask == NULL)
        {
            xTCB = (TCB_t *) pxCurrentTCB;
        }
        else
        {
            xTCB = xTask;
        }

        /* Save the hook function in the TCB.  A critical section is required as
         * the value can be accessed from an interrupt. */
        taskENTER_CRITICAL();
        {
            xTCB->pxTaskTag = pxHookFunction;
        }
        taskEXIT_CRITICAL();
    }

    TaskHookFunction_t xTaskGetApplicationTaskTag(TaskHandle_t xTask)
    {
        TCB_t * pxTCB;
        TaskHookFunction_t xReturn;

        /* If xTask is NULL then set the calling task's hook. */
        pxTCB = prvGetTCBFromHandle(xTask);

        /* Save the hook function in the TCB.  A critical section is required as
         * the value can be accessed from an interrupt. */
        taskENTER_CRITICAL();
        {
            xReturn = pxTCB->pxTaskTag;
        }
        taskEXIT_CRITICAL();

        return xReturn;
    }

    TaskHookFunction_t xTaskGetApplicationTaskTagFromISR(TaskHandle_t xTask)
    {
        TCB_t * pxTCB;
        TaskHookFunction_t xReturn;
        UBaseType_t uxSavedInterruptStatus;

        /* If xTask is NULL then set the calling task's hook. */
        pxTCB = prvGetTCBFromHandle(xTask);

        /* Save the hook function in the TCB.  A critical section is required as
         * the value can be accessed from an interrupt. */
        uxSavedInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
        {
            xReturn = pxTCB->pxTaskTag;
        }
        portCLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptStatus);

        return xReturn;
    }

    BaseType_t xTaskCallApplicationTaskHook(TaskHandle_t xTask,
                                             void * pvParameter)
    {
        TCB_t * xTCB;
        BaseType_t xReturn;

        /* If xTask is NULL then we are calling our own task hook. */
        if (xTask == NULL)
        {
            xTCB = pxCurrentTCB;
        }
        else
        {
            xTCB = xTask;
        }

        if (xTCB->pxTaskTag != NULL)
        {
            xReturn = xTCB->pxTaskTag(pvParameter);
        }
        else
        {
            xReturn = pdFAIL;
        }

        return xReturn;
    }

#endif /* configUSE_APPLICATION_TASK_TAG */

void vTaskSwitchContext(void)
{
    /* 调度器处于挂起状态 */
    if (uxSchedulerSuspended != (UBaseType_t)pdFALSE) {
        /**
         * The scheduler is currently suspended - do not allow a context
         * switch.
         */
        xYieldPending = pdTRUE;
    } else {
        xYieldPending = pdFALSE;
        traceTASK_SWITCHED_OUT();

        #if (configGENERATE_RUN_TIME_STATS == 1)
        {
            #ifdef portALT_GET_RUN_TIME_COUNTER_VALUE
                portALT_GET_RUN_TIME_COUNTER_VALUE(ulTotalRunTime);
            #else
                ulTotalRunTime = portGET_RUN_TIME_COUNTER_VALUE();
            #endif

            /* Add the amount of time the task has been running to the
             * accumulated time so far.  The time the task started running was
             * stored in ulTaskSwitchedInTime.  Note that there is no overflow
             * protection here so count values are only valid until the timer
             * overflows.  The guard against negative values is to protect
             * against suspect run time stat counter implementations - which
             * are provided by the application, not the kernel. */
            if (ulTotalRunTime > ulTaskSwitchedInTime)
            {
                pxCurrentTCB->ulRunTimeCounter += (ulTotalRunTime - ulTaskSwitchedInTime);
            }

            ulTaskSwitchedInTime = ulTotalRunTime;
        }
        #endif /* configGENERATE_RUN_TIME_STATS */

        /* Check for stack overflow, if configured. */
        taskCHECK_FOR_STACK_OVERFLOW();

        /* Before the currently running task is switched out, save its errno. */
        #if (configUSE_POSIX_ERRNO == 1)
        {
            pxCurrentTCB->iTaskErrno = FreeRTOS_errno;
        }
        #endif

        /**
         * Select a new task to run using either the generic C or port
         * optimised asm code.
         * 选择优先级最高的任务
         */
        taskSELECT_HIGHEST_PRIORITY_TASK();
        traceTASK_SWITCHED_IN();

        /* After the new task is switched in, update the global errno. */
        #if (configUSE_POSIX_ERRNO == 1)
        {
            FreeRTOS_errno = pxCurrentTCB->iTaskErrno;
        }
        #endif

        #if ((configUSE_NEWLIB_REENTRANT == 1) || (configUSE_C_RUNTIME_TLS_SUPPORT == 1))
        {
            /* Switch C-Runtime's TLS Block to point to the TLS
             * Block specific to this task. */
            configSET_TLS_BLOCK(pxCurrentTCB->xTLSBlock);
        }
        #endif
    }
}

void vTaskPlaceOnEventList(List_t * const pxEventList,
                            const TickType_t xTicksToWait)
{
    configASSERT(pxEventList);

    /* THIS FUNCTION MUST BE CALLED WITH EITHER INTERRUPTS DISABLED OR THE
     * SCHEDULER SUSPENDED AND THE QUEUE BEING ACCESSED LOCKED. */

    /* Place the event list item of the TCB in the appropriate event list.
     * This is placed in the list in priority order so the highest priority task
     * is the first to be woken by the event.
     *
     * Note: Lists are sorted in ascending order by ListItem_t.xItemValue.
     * Normally, the xItemValue of a TCB's ListItem_t members is:
     *      xItemValue = (configMAX_PRIORITIES - uxPriority)
     * Therefore, the event list is sorted in descending priority order.
     *
     * The queue that contains the event list is locked, preventing
     * simultaneous access from interrupts. */
    vListInsert(pxEventList, &(pxCurrentTCB->xEventListItem));

    prvAddCurrentTaskToDelayedList(xTicksToWait, pdTRUE);
}


void vTaskPlaceOnUnorderedEventList(List_t * pxEventList,
                                     const TickType_t xItemValue,
                                     const TickType_t xTicksToWait)
{
    configASSERT(pxEventList);

    /* THIS FUNCTION MUST BE CALLED WITH THE SCHEDULER SUSPENDED.  It is used by
     * the event groups implementation. */
    configASSERT(uxSchedulerSuspended != 0);

    /* Store the item value in the event list item.  It is safe to access the
     * event list item here as interrupts won't access the event list item of a
     * task that is not in the Blocked state. */
    listSET_LIST_ITEM_VALUE(&(pxCurrentTCB->xEventListItem), xItemValue | taskEVENT_LIST_ITEM_VALUE_IN_USE);

    /* Place the event list item of the TCB at the end of the appropriate event
     * list.  It is safe to access the event list here because it is part of an
     * event group implementation - and interrupts don't access event groups
     * directly (instead they access them indirectly by pending function calls to
     * the task level).
     * 任务加入事件队列
     */
    listINSERT_END(pxEventList, &(pxCurrentTCB->xEventListItem));

    /* 任务加入延迟队列 */
    prvAddCurrentTaskToDelayedList(xTicksToWait, pdTRUE);
}


#if (configUSE_TIMERS == 1)

    void vTaskPlaceOnEventListRestricted(List_t * const pxEventList,
                                          TickType_t xTicksToWait,
                                          const BaseType_t xWaitIndefinitely)
    {
        configASSERT(pxEventList);

        /* This function should not be called by application code hence the
         * 'Restricted' in its name.  It is not part of the public API.  It is
         * designed for use by kernel code, and has special calling requirements -
         * it should be called with the scheduler suspended. */


        /* Place the event list item of the TCB in the appropriate event list.
         * In this case it is assume that this is the only task that is going to
         * be waiting on this event list, so the faster vListInsertEnd() function
         * can be used in place of vListInsert. */
        listINSERT_END(pxEventList, &(pxCurrentTCB->xEventListItem));

        /* If the task should block indefinitely then set the block time to a
         * value that will be recognised as an indefinite delay inside the
         * prvAddCurrentTaskToDelayedList() function. */
        if (xWaitIndefinitely != pdFALSE)
        {
            xTicksToWait = portMAX_DELAY;
        }

        traceTASK_DELAY_UNTIL((xTickCount + xTicksToWait));
        prvAddCurrentTaskToDelayedList(xTicksToWait, xWaitIndefinitely);
    }

#endif /* configUSE_TIMERS */


BaseType_t xTaskRemoveFromEventList(const List_t * const pxEventList)
{
    TCB_t * pxUnblockedTCB;
    BaseType_t xReturn;

    /* THIS FUNCTION MUST BE CALLED FROM A CRITICAL SECTION.  It can also be
     * called from a critical section within an ISR. */

    /* The event list is sorted in priority order, so the first in the list can
     * be removed as it is known to be the highest priority.  Remove the TCB from
     * the delayed list, and add it to the ready list.
     *
     * If an event is for a queue that is locked then this function will never
     * get called - the lock count on the queue will get modified instead.  This
     * means exclusive access to the event list is guaranteed here.
     *
     * This function assumes that a check has already been made to ensure that
     * pxEventList is not empty. */
    pxUnblockedTCB = listGET_OWNER_OF_HEAD_ENTRY(pxEventList);
    configASSERT(pxUnblockedTCB);
    listREMOVE_ITEM(&(pxUnblockedTCB->xEventListItem));

    /* 如果调度器正在运行中 */
    if (uxSchedulerSuspended == (UBaseType_t)pdFALSE)
    {
        listREMOVE_ITEM(&(pxUnblockedTCB->xStateListItem));
        /* 任务重新加入就绪队列 */
        prvAddTaskToReadyList(pxUnblockedTCB);

        #if (configUSE_TICKLESS_IDLE != 0)
        {
            /* If a task is blocked on a kernel object then xNextTaskUnblockTime
             * might be set to the blocked task's time out time.  If the task is
             * unblocked for a reason other than a timeout xNextTaskUnblockTime is
             * normally left unchanged, because it is automatically reset to a new
             * value when the tick count equals xNextTaskUnblockTime.  However if
             * tickless idling is used it might be more important to enter sleep mode
             * at the earliest possible time - so reset xNextTaskUnblockTime here to
             * ensure it is updated at the earliest possible time. */
            prvResetNextTaskUnblockTime();
        }
        #endif
    }
    else
    {
        /* The delayed and ready lists cannot be accessed, so hold this task
         * pending until the scheduler is resumed.
         * 调度器被挂起状态，将任务加入到等待加入就绪队列链表
         */
        listINSERT_END(&(xPendingReadyList), &(pxUnblockedTCB->xEventListItem));
    }

    /**
     * pxUnblockedTCB任务优先级比当前正在运行任务的优先级要高，当前任务被抢占
     */
    if (pxUnblockedTCB->uxPriority > pxCurrentTCB->uxPriority)
    {
        /* Return true if the task removed from the event list has a higher
         * priority than the calling task.  This allows the calling task to know if
         * it should force a context switch now. */
        xReturn = pdTRUE;

        /**
         * Mark that a yield is pending in case the user is not using the
         * "xHigherPriorityTaskWoken" parameter to an ISR safe FreeRTOS function.
         * 设置可抢占标记
         */
        xYieldPending = pdTRUE;
    }
    else
    {
        xReturn = pdFALSE;
    }

    return xReturn;
}

void vTaskRemoveFromUnorderedEventList(ListItem_t * pxEventListItem,
                                        const TickType_t xItemValue)
{
    TCB_t * pxUnblockedTCB;

    /* THIS FUNCTION MUST BE CALLED WITH THE SCHEDULER SUSPENDED.  It is used by
     * the event flags implementation. */
    configASSERT(uxSchedulerSuspended != pdFALSE);

    /* Store the new item value in the event list. */
    listSET_LIST_ITEM_VALUE(pxEventListItem, xItemValue|taskEVENT_LIST_ITEM_VALUE_IN_USE);

    /* Remove the event list form the event flag.  Interrupts do not access
     * event flags. */
    pxUnblockedTCB = listGET_LIST_ITEM_OWNER(pxEventListItem);
    configASSERT(pxUnblockedTCB);
    listREMOVE_ITEM(pxEventListItem);

    #if (configUSE_TICKLESS_IDLE != 0)
    {
        /* If a task is blocked on a kernel object then xNextTaskUnblockTime
         * might be set to the blocked task's time out time.  If the task is
         * unblocked for a reason other than a timeout xNextTaskUnblockTime is
         * normally left unchanged, because it is automatically reset to a new
         * value when the tick count equals xNextTaskUnblockTime.  However if
         * tickless idling is used it might be more important to enter sleep mode
         * at the earliest possible time - so reset xNextTaskUnblockTime here to
         * ensure it is updated at the earliest possible time. */
        prvResetNextTaskUnblockTime();
    }
    #endif

    /* Remove the task from the delayed list and add it to the ready list.  The
     * scheduler is suspended so interrupts will not be accessing the ready
     * lists. */
    listREMOVE_ITEM(&(pxUnblockedTCB->xStateListItem));
    /* 加入任务就绪队列 */
    prvAddTaskToReadyList(pxUnblockedTCB);

    if (pxUnblockedTCB->uxPriority > pxCurrentTCB->uxPriority)
    {
        /* The unblocked task has a priority above that of the calling task, so
         * a context switch is required.  This function is called with the
         * scheduler suspended so xYieldPending is set so the context switch
         * occurs immediately that the scheduler is resumed (unsuspended). */
        xYieldPending = pdTRUE;
    }
}

void vTaskSetTimeOutState(TimeOut_t * const pxTimeOut)
{
    configASSERT(pxTimeOut);
    taskENTER_CRITICAL();
    {
        pxTimeOut->xOverflowCount = xNumOfOverflows;
        pxTimeOut->xTimeOnEntering = xTickCount;
    }
    taskEXIT_CRITICAL();
}


void vTaskInternalSetTimeOutState(TimeOut_t * const pxTimeOut)
{
    /* For internal use only as it does not use a critical section. */
    pxTimeOut->xOverflowCount = xNumOfOverflows;
    pxTimeOut->xTimeOnEntering = xTickCount;
}


/**
 * 检查是否已经超过pxTicksToWait
 */
BaseType_t xTaskCheckForTimeOut(TimeOut_t * const pxTimeOut,
                                 TickType_t * const pxTicksToWait)
{
    BaseType_t xReturn;

    configASSERT(pxTimeOut);
    configASSERT(pxTicksToWait);

    taskENTER_CRITICAL();
    {
        /* Minor optimisation.  The tick count cannot change in this block. */
        const TickType_t xConstTickCount = xTickCount;
        /* 计算出pxTimeOut初始设置到现在，已经经过的tick */
        const TickType_t xElapsedTime = xConstTickCount - pxTimeOut->xTimeOnEntering;

        #if (INCLUDE_xTaskAbortDelay == 1)
            if (pxCurrentTCB->ucDelayAborted != (uint8_t)pdFALSE)
            {
                /* The delay was aborted, which is not the same as a time out,
                 * but has the same result. */
                pxCurrentTCB->ucDelayAborted = pdFALSE;
                xReturn = pdTRUE;
            }
            else
        #endif

        #if (INCLUDE_vTaskSuspend == 1)
            if (*pxTicksToWait == portMAX_DELAY)
            {
                /* If INCLUDE_vTaskSuspend is set to 1 and the block time
                 * specified is the maximum block time then the task should block
                 * indefinitely, and therefore never time out. */
                xReturn = pdFALSE;
            }
            else
        #endif

        if ((xNumOfOverflows != pxTimeOut->xOverflowCount) && (xConstTickCount >= pxTimeOut->xTimeOnEntering))
        {
            /* The tick count is greater than the time at which
             * vTaskSetTimeout() was called, but has also overflowed since
             * vTaskSetTimeOut() was called.  It must have wrapped all the way
             * around and gone past again. This passed since vTaskSetTimeout()
             * was called.
             * 已经超时
             */
            xReturn = pdTRUE;
            *pxTicksToWait = (TickType_t)0;
        }
        else if (xElapsedTime < *pxTicksToWait)
        {
            /* Not a genuine timeout. Adjust parameters for time remaining. */
            *pxTicksToWait -= xElapsedTime;
            vTaskInternalSetTimeOutState(pxTimeOut);
            xReturn = pdFALSE;
        }
        else
        {
            *pxTicksToWait = (TickType_t)0;
            xReturn = pdTRUE;
        }
    }
    taskEXIT_CRITICAL();

    return xReturn;
}


void vTaskMissedYield(void)
{
    xYieldPending = pdTRUE;
}

#if (configUSE_TRACE_FACILITY == 1)

UBaseType_t uxTaskGetTaskNumber(TaskHandle_t xTask)
{
    UBaseType_t uxReturn;
    TCB_t const * pxTCB;
    if (xTask != NULL)
    {
        pxTCB = xTask;
        uxReturn = pxTCB->uxTaskNumber;
    }
    else
    {
        uxReturn = 0U;
    }
    return uxReturn;
}

void vTaskSetTaskNumber(TaskHandle_t xTask,
                         const UBaseType_t uxHandle)
{
    TCB_t * pxTCB;
    if (xTask != NULL)
    {
        pxTCB = xTask;
        pxTCB->uxTaskNumber = uxHandle;
    }
}

#endif /* configUSE_TRACE_FACILITY */

/*
 * -----------------------------------------------------------
 * The Idle task.
 * ----------------------------------------------------------
 *
 * The portTASK_FUNCTION() macro is used to allow port/compiler specific
 * language extensions.  The equivalent prototype for this function is:
 *
 * void prvIdleTask(void *pvParameters);
 * 系统idle任务
 */
static portTASK_FUNCTION(prvIdleTask, pvParameters)
{
    /* Stop warnings. */
    (void)pvParameters;

    /** THIS IS THE RTOS IDLE TASK - WHICH IS CREATED AUTOMATICALLY WHEN THE
     * SCHEDULER IS STARTED. **/

    /* In case a task that has a secure context deletes itself, in which case
     * the idle task is responsible for deleting the task's secure context, if
     * any. */
    portALLOCATE_SECURE_CONTEXT(configMINIMAL_SECURE_STACK_SIZE);

    for (; ;)
    {
        /**
         * See if any tasks have deleted themselves - if so then the idle task
         * is responsible for freeing the deleted task's TCB and stack.
         * 释放已经删除任务的任务控制块占用的内存
         */
        prvCheckTasksWaitingTermination();

        #if (configUSE_PREEMPTION == 0)
        {
            /* If we are not using preemption we keep forcing a task switch to
             * see if any other task has become available.  If we are using
             * preemption we don't need to do this as any task becoming available
             * will automatically get the processor anyway.
             * 不开启内核抢占的话，主动触发任务调度，看看，是否有其他任务可以运行
             */
            taskYIELD();
        }
        #endif

        /*
         * 开启抢占的情况下，用户空间创建了与idle相同优先级的任务，则用户空间的任务是可以
         * 使用空闲任务的时间片
         */
        #if ((configUSE_PREEMPTION == 1) && (configIDLE_SHOULD_YIELD == 1))
        {
            /* When using preemption tasks of equal priority will be
             * timesliced.  If a task that is sharing the idle priority is ready
             * to run then the idle task should yield before the end of the
             * timeslice.
             *
             * A critical region is not required here as we are just reading from
             * the list, and an occasional incorrect value will not matter.  If
             * the ready list at the idle priority contains more than one task
             * then a task other than the idle task is ready to execute.
             * 有和空闲任务相同优先级的用户任务，则空闲任务让出cpu
             */
            if (listCURRENT_LIST_LENGTH(&(pxReadyTasksLists[tskIDLE_PRIORITY])) > (UBaseType_t)1)
            {
                taskYIELD();
            }
        }
        #endif

        #if (configUSE_IDLE_HOOK == 1)
        {
            extern void vApplicationIdleHook(void);

            /* Call the user defined function from within the idle task.  This
             * allows the application designer to add background functionality
             * without the overhead of a separate task.
             * NOTE: vApplicationIdleHook() MUST NOT, UNDER ANY CIRCUMSTANCES,
             * CALL A FUNCTION THAT MIGHT BLOCK. */
            vApplicationIdleHook();
        }
        #endif /* configUSE_IDLE_HOOK */

        /* This conditional compilation should use inequality to 0, not equality
         * to 1.  This is to ensure portSUPPRESS_TICKS_AND_SLEEP() is called when
         * user defined low power mode  implementations require
         * configUSE_TICKLESS_IDLE to be set to a value other than 1.
         * 进入低功耗模式
         */
        #if (configUSE_TICKLESS_IDLE != 0)
        {
            TickType_t xExpectedIdleTime;

            /* It is not desirable to suspend then resume the scheduler on
             * each iteration of the idle task.  Therefore, a preliminary
             * test of the expected idle time is performed without the
             * scheduler suspended.  The result here is not necessarily
             * valid.
             * 计算出系统期望运行在低功耗模式的节拍数
             */
            xExpectedIdleTime = prvGetExpectedIdleTime();

            /* 满足系统配置的进入低功耗模式的阈值 */
            if (xExpectedIdleTime >= configEXPECTED_IDLE_TIME_BEFORE_SLEEP)
            {
                vTaskSuspendAll();
                {
                    /* Now the scheduler is suspended, the expected idle
                     * time can be sampled again, and this time its value can
                     * be used. */
                    configASSERT(xNextTaskUnblockTime >= xTickCount);
                    /* 再次计算出系统期望运行在低功耗模式的节拍数 */
                    xExpectedIdleTime = prvGetExpectedIdleTime();

                    /* Define the following macro to set xExpectedIdleTime to 0
                     * if the application does not want
                     * portSUPPRESS_TICKS_AND_SLEEP() to be called. */
                    configPRE_SUPPRESS_TICKS_AND_SLEEP_PROCESSING(xExpectedIdleTime);

                    /* 满足系统配置的进入低功耗模式的阈值 */
                    if (xExpectedIdleTime >= configEXPECTED_IDLE_TIME_BEFORE_SLEEP)
                    {
                        traceLOW_POWER_IDLE_BEGIN();
                        /* 处理器进入低功耗模式 */
                        portSUPPRESS_TICKS_AND_SLEEP(xExpectedIdleTime);
                        traceLOW_POWER_IDLE_END();
                    }
                }
                /* 此处，应该是只退出低功耗模式后，才能指向到这里 */
                (void) xTaskResumeAll();
            }
        }
        #endif
    }
}

#if (configUSE_TICKLESS_IDLE != 0)

eSleepModeStatus eTaskConfirmSleepModeStatus(void)
{
#if (INCLUDE_vTaskSuspend == 1)
    /* The idle task exists in addition to the application tasks. */
    const UBaseType_t uxNonApplicationTasks = 1;
#endif /* INCLUDE_vTaskSuspend */
    eSleepModeStatus eReturn = eStandardSleep;
    /* This function must be called from a critical section. */
    if (listCURRENT_LIST_LENGTH(&xPendingReadyList) != 0)
    {
        /**
         * A task was made ready while the scheduler was suspended.
         * 有任务就绪，放弃休眠
         */
        eReturn = eAbortSleep;
    }
    else if (xYieldPending == pdTRUE)
    {
        /* A yield was pended while the scheduler was suspended. */
        eReturn = eAbortSleep;
    }
    else if (xPendedTicks != 0)
    {
        /* A tick interrupt has already occurred but was held pending
         * because the scheduler is suspended. */
        eReturn = eAbortSleep;
    }
#if (INCLUDE_vTaskSuspend == 1)
    else if (listCURRENT_LIST_LENGTH(&xSuspendedTaskList) == (uxCurrentNumberOfTasks - uxNonApplicationTasks))
    {
        /* If all the tasks are in the suspended list (which might mean they
         * have an infinite block time rather than actually being suspended)
         * then it is safe to turn all clocks off and just wait for external
         * interrupts. */
        eReturn = eNoTasksWaitingTimeout;
    }
#endif /* INCLUDE_vTaskSuspend */
    return eReturn;
}

#endif

#if (configNUM_THREAD_LOCAL_STORAGE_POINTERS != 0)

void vTaskSetThreadLocalStoragePointer(TaskHandle_t xTaskToSet,
                                        BaseType_t xIndex,
                                        void * pvValue)
{
    TCB_t * pxTCB;
    if ((xIndex >= 0) &&
        (xIndex < configNUM_THREAD_LOCAL_STORAGE_POINTERS))
    {
        pxTCB = prvGetTCBFromHandle(xTaskToSet);
        configASSERT(pxTCB != NULL);
        pxTCB->pvThreadLocalStoragePointers[xIndex] = pvValue;
    }
}

#endif /* configNUM_THREAD_LOCAL_STORAGE_POINTERS */

#if (configNUM_THREAD_LOCAL_STORAGE_POINTERS != 0)

void * pvTaskGetThreadLocalStoragePointer(TaskHandle_t xTaskToQuery,
                                           BaseType_t xIndex)
{
    void * pvReturn = NULL;
    TCB_t * pxTCB;
    if ((xIndex >= 0) &&
        (xIndex < configNUM_THREAD_LOCAL_STORAGE_POINTERS))
    {
        pxTCB = prvGetTCBFromHandle(xTaskToQuery);
        pvReturn = pxTCB->pvThreadLocalStoragePointers[xIndex];
    }
    else
    {
        pvReturn = NULL;
    }
    return pvReturn;
}

#endif /* configNUM_THREAD_LOCAL_STORAGE_POINTERS */


#if (portUSING_MPU_WRAPPERS == 1)

    void vTaskAllocateMPURegions(TaskHandle_t xTaskToModify,
                                  const MemoryRegion_t * const xRegions)
    {
        TCB_t * pxTCB;

        /* If null is passed in here then we are modifying the MPU settings of
         * the calling task. */
        pxTCB = prvGetTCBFromHandle(xTaskToModify);

        vPortStoreTaskMPUSettings(&(pxTCB->xMPUSettings), xRegions, NULL, 0);
    }

#endif /* portUSING_MPU_WRAPPERS */


static void prvInitialiseTaskLists(void)
{
    UBaseType_t uxPriority;

    for (uxPriority = (UBaseType_t)0U; uxPriority < (UBaseType_t)configMAX_PRIORITIES; uxPriority++)
        vListInitialise(&(pxReadyTasksLists[uxPriority]));

    vListInitialise(&xDelayedTaskList1);
    vListInitialise(&xDelayedTaskList2);
    vListInitialise(&xPendingReadyList);

    #if (INCLUDE_vTaskDelete == 1)
    {
        vListInitialise(&xTasksWaitingTermination);
    }
    #endif /* INCLUDE_vTaskDelete */

    #if (INCLUDE_vTaskSuspend == 1)
    {
        vListInitialise(&xSuspendedTaskList);
    }
    #endif /* INCLUDE_vTaskSuspend */

    /**
     * Start with pxDelayedTaskList using list1 and the pxOverflowDelayedTaskList
     * using list2.
     */
    pxDelayedTaskList = &xDelayedTaskList1;
    pxOverflowDelayedTaskList = &xDelayedTaskList2;
}

/**
 * 检查释放已删除任务占用的内存
 */
static void prvCheckTasksWaitingTermination(void)
{
    /** THIS FUNCTION IS CALLED FROM THE RTOS IDLE TASK **/

    #if (INCLUDE_vTaskDelete == 1)
    {
        TCB_t * pxTCB;

        /* uxDeletedTasksWaitingCleanUp is used to prevent taskENTER_CRITICAL()
         * being called too often in the idle task. */
        while (uxDeletedTasksWaitingCleanUp > (UBaseType_t)0U)
        {
            taskENTER_CRITICAL();
            {
                /* 从终止队列中删除 */
                pxTCB = listGET_OWNER_OF_HEAD_ENTRY((&xTasksWaitingTermination));
                (void) uxListRemove(&(pxTCB->xStateListItem));
                --uxCurrentNumberOfTasks;
                --uxDeletedTasksWaitingCleanUp;
            }
            taskEXIT_CRITICAL();
            /* 释放任务控制块占用的内存 */
            prvDeleteTCB(pxTCB);
        }
    }
    #endif /* INCLUDE_vTaskDelete */
}

#if (configUSE_TRACE_FACILITY == 1)

    void vTaskGetInfo(TaskHandle_t xTask,
                       TaskStatus_t * pxTaskStatus,
                       BaseType_t xGetFreeStackSpace,
                       eTaskState eState)
    {
        TCB_t * pxTCB;

        /* xTask is NULL then get the state of the calling task. */
        pxTCB = prvGetTCBFromHandle(xTask);

        pxTaskStatus->xHandle = (TaskHandle_t) pxTCB;
        pxTaskStatus->pcTaskName = (const char *) &(pxTCB->pcTaskName[0]);
        pxTaskStatus->uxCurrentPriority = pxTCB->uxPriority;
        pxTaskStatus->pxStackBase = pxTCB->pxStack;
        #if ((portSTACK_GROWTH > 0) && (configRECORD_STACK_HIGH_ADDRESS == 1))
            pxTaskStatus->pxTopOfStack = pxTCB->pxTopOfStack;
            pxTaskStatus->pxEndOfStack = pxTCB->pxEndOfStack;
        #endif
        pxTaskStatus->xTaskNumber = pxTCB->uxTCBNumber;

        #if (configUSE_MUTEXES == 1)
        {
            pxTaskStatus->uxBasePriority = pxTCB->uxBasePriority;
        }
        #else
        {
            pxTaskStatus->uxBasePriority = 0;
        }
        #endif

        #if (configGENERATE_RUN_TIME_STATS == 1)
        {
            pxTaskStatus->ulRunTimeCounter = pxTCB->ulRunTimeCounter;
        }
        #else
        {
            pxTaskStatus->ulRunTimeCounter = (configRUN_TIME_COUNTER_TYPE) 0;
        }
        #endif

        /* Obtaining the task state is a little fiddly, so is only done if the
         * value of eState passed into this function is eInvalid - otherwise the
         * state is just set to whatever is passed in. */
        if (eState != eInvalid)
        {
            if (pxTCB == pxCurrentTCB)
            {
                pxTaskStatus->eCurrentState = eRunning;
            }
            else
            {
                pxTaskStatus->eCurrentState = eState;

                #if (INCLUDE_vTaskSuspend == 1)
                {
                    /* If the task is in the suspended list then there is a
                     *  chance it is actually just blocked indefinitely - so really
                     *  it should be reported as being in the Blocked state. */
                    if (eState == eSuspended)
                    {
                        vTaskSuspendAll();
                        {
                            if (listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) != NULL)
                            {
                                pxTaskStatus->eCurrentState = eBlocked;
                            }
                        }
                        (void) xTaskResumeAll();
                    }
                }
                #endif /* INCLUDE_vTaskSuspend */
            }
        }
        else
        {
            pxTaskStatus->eCurrentState = eTaskGetState(pxTCB);
        }

        /* Obtaining the stack space takes some time, so the xGetFreeStackSpace
         * parameter is provided to allow it to be skipped. */
        if (xGetFreeStackSpace != pdFALSE)
        {
            #if (portSTACK_GROWTH > 0)
            {
                pxTaskStatus->usStackHighWaterMark = prvTaskCheckFreeStackSpace((uint8_t *) pxTCB->pxEndOfStack);
            }
            #else
            {
                pxTaskStatus->usStackHighWaterMark = prvTaskCheckFreeStackSpace((uint8_t *) pxTCB->pxStack);
            }
            #endif
        }
        else
        {
            pxTaskStatus->usStackHighWaterMark = 0;
        }
    }

#endif /* configUSE_TRACE_FACILITY */


#if (configUSE_TRACE_FACILITY == 1)

    static UBaseType_t prvListTasksWithinSingleList(TaskStatus_t * pxTaskStatusArray,
                                                     List_t * pxList,
                                                     eTaskState eState)
    {
        configLIST_VOLATILE TCB_t * pxNextTCB;
        configLIST_VOLATILE TCB_t * pxFirstTCB;
        UBaseType_t uxTask = 0;

        if (listCURRENT_LIST_LENGTH(pxList) > (UBaseType_t) 0)
        {
            listGET_OWNER_OF_NEXT_ENTRY(pxFirstTCB, pxList);

            /* Populate an TaskStatus_t structure within the
             * pxTaskStatusArray array for each task that is referenced from
             * pxList.  See the definition of TaskStatus_t in task.h for the
             * meaning of each TaskStatus_t structure member. */
            do
            {
                listGET_OWNER_OF_NEXT_ENTRY(pxNextTCB, pxList);
                vTaskGetInfo((TaskHandle_t) pxNextTCB, &(pxTaskStatusArray[uxTask]), pdTRUE, eState);
                uxTask++;
            } while (pxNextTCB != pxFirstTCB);
        }

        return uxTask;
    }

#endif /* configUSE_TRACE_FACILITY */


#if ((configUSE_TRACE_FACILITY == 1) || (INCLUDE_uxTaskGetStackHighWaterMark == 1) || (INCLUDE_uxTaskGetStackHighWaterMark2 == 1))

    static configSTACK_DEPTH_TYPE prvTaskCheckFreeStackSpace(const uint8_t * pucStackByte)
    {
        uint32_t ulCount = 0U;

        while (*pucStackByte == (uint8_t) tskSTACK_FILL_BYTE)
        {
            pucStackByte -= portSTACK_GROWTH;
            ulCount++;
        }

        ulCount /= (uint32_t) sizeof(StackType_t); /*lint !e961 Casting is not redundant on smaller architectures. */

        return (configSTACK_DEPTH_TYPE) ulCount;
    }

#endif


#if (INCLUDE_uxTaskGetStackHighWaterMark2 == 1)

/* uxTaskGetStackHighWaterMark() and uxTaskGetStackHighWaterMark2() are the
 * same except for their return type.  Using configSTACK_DEPTH_TYPE allows the
 * user to determine the return type.  It gets around the problem of the value
 * overflowing on 8-bit types without breaking backward compatibility for
 * applications that expect an 8-bit return type. */
    configSTACK_DEPTH_TYPE uxTaskGetStackHighWaterMark2(TaskHandle_t xTask)
    {
        TCB_t * pxTCB;
        uint8_t * pucEndOfStack;
        configSTACK_DEPTH_TYPE uxReturn;

        /* uxTaskGetStackHighWaterMark() and uxTaskGetStackHighWaterMark2() are
         * the same except for their return type.  Using configSTACK_DEPTH_TYPE
         * allows the user to determine the return type.  It gets around the
         * problem of the value overflowing on 8-bit types without breaking
         * backward compatibility for applications that expect an 8-bit return
         * type. */

        pxTCB = prvGetTCBFromHandle(xTask);

        #if portSTACK_GROWTH < 0
        {
            pucEndOfStack = (uint8_t *) pxTCB->pxStack;
        }
        #else
        {
            pucEndOfStack = (uint8_t *) pxTCB->pxEndOfStack;
        }
        #endif

        uxReturn = prvTaskCheckFreeStackSpace(pucEndOfStack);

        return uxReturn;
    }

#endif /* INCLUDE_uxTaskGetStackHighWaterMark2 */

#if (INCLUDE_uxTaskGetStackHighWaterMark == 1)

    UBaseType_t uxTaskGetStackHighWaterMark(TaskHandle_t xTask)
    {
        TCB_t * pxTCB;
        uint8_t * pucEndOfStack;
        UBaseType_t uxReturn;

        pxTCB = prvGetTCBFromHandle(xTask);

        #if portSTACK_GROWTH < 0
        {
            pucEndOfStack = (uint8_t *) pxTCB->pxStack;
        }
        #else
        {
            pucEndOfStack = (uint8_t *) pxTCB->pxEndOfStack;
        }
        #endif

        uxReturn = (UBaseType_t) prvTaskCheckFreeStackSpace(pucEndOfStack);

        return uxReturn;
    }

#endif /* INCLUDE_uxTaskGetStackHighWaterMark */


#if (INCLUDE_vTaskDelete == 1)

static void prvDeleteTCB(TCB_t *pxTCB)
{
    /* This call is required specifically for the TriCore port.  It must be
     * above the vPortFree() calls.  The call is also used by ports/demos that
     * want to allocate and clean RAM statically. */
    portCLEAN_UP_TCB(pxTCB);
    #if ((configUSE_NEWLIB_REENTRANT == 1) || (configUSE_C_RUNTIME_TLS_SUPPORT == 1))
    {
        /* Free up the memory allocated for the task's TLS Block. */
        configDEINIT_TLS_BLOCK(pxCurrentTCB->xTLSBlock);
    }
    #endif
    #if (portUSING_MPU_WRAPPERS == 0)
    {
        /**
         * The task can only have been allocated dynamically - free both
         * the stack and TCB.
         * 释放任务的堆栈内存和任务控制块内存
         */
        vPortFreeStack(pxTCB->pxStack);
        vPortFree(pxTCB);
    }
    #elif (tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE != 0)
    {
        /* The task could have been allocated statically or dynamically, so
         * check what was statically allocated before trying to free the
         * memory. */
        if (pxTCB->ucStaticallyAllocated == tskDYNAMICALLY_ALLOCATED_STACK_AND_TCB)
        {
            /* Both the stack and TCB were allocated dynamically, so both
             * must be freed. */
            vPortFreeStack(pxTCB->pxStack);
            vPortFree(pxTCB);
        }
        else if (pxTCB->ucStaticallyAllocated == tskSTATICALLY_ALLOCATED_STACK_ONLY)
        {
            /* Only the stack was statically allocated, so the TCB is the
             * only memory that must be freed. */
            vPortFree(pxTCB);
        }
        else
        {
            /* Neither the stack nor the TCB were allocated dynamically, so
             * nothing needs to be freed. */
            configASSERT(pxTCB->ucStaticallyAllocated == tskSTATICALLY_ALLOCATED_STACK_AND_TCB);
        }
    }
    #endif
}

#endif /* INCLUDE_vTaskDelete */


static void prvResetNextTaskUnblockTime(void)
{
    /* 延迟队列为空 */
    if (listLIST_IS_EMPTY(pxDelayedTaskList) != pdFALSE)
    {
        /**
         * The new current delayed list is empty.  Set xNextTaskUnblockTime to
         * the maximum possible value so it is  extremely unlikely that the
         * if (xTickCount >= xNextTaskUnblockTime) test will pass until
         * there is an item in the delayed list.
         */
        xNextTaskUnblockTime = portMAX_DELAY;
    }
    else
    {
        /**
         * The new current delayed list is not empty, get the value of
         * the item at the head of the delayed list.  This is the time at
         * which the task at the head of the delayed list should be removed
         * from the Blocked state.
         * 下一个等待超时的时间
         */
        xNextTaskUnblockTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY(pxDelayedTaskList);
    }
}


#if ((INCLUDE_xTaskGetCurrentTaskHandle == 1) || (configUSE_MUTEXES == 1))

    TaskHandle_t xTaskGetCurrentTaskHandle(void)
    {
        TaskHandle_t xReturn;

        /* A critical section is not required as this is not called from
         * an interrupt and the current TCB will always be the same for any
         * individual execution thread. */
        xReturn = pxCurrentTCB;

        return xReturn;
    }

#endif /* ((INCLUDE_xTaskGetCurrentTaskHandle == 1) || (configUSE_MUTEXES == 1)) */


#if ((INCLUDE_xTaskGetSchedulerState == 1) || (configUSE_TIMERS == 1))

/**
 * 检查调度器状态
 */
BaseType_t xTaskGetSchedulerState(void)
{
    BaseType_t xReturn;
    if (xSchedulerRunning == pdFALSE)
    {
        xReturn = taskSCHEDULER_NOT_STARTED;
    }
    else
    {
        if (uxSchedulerSuspended == (UBaseType_t)pdFALSE)
        {
            xReturn = taskSCHEDULER_RUNNING;
        }
        else
        {
            xReturn = taskSCHEDULER_SUSPENDED;
        }
    }
    return xReturn;
}

#endif

#if (configUSE_MUTEXES == 1)

/**
 * @pxMutexHolder: 持有互斥锁的任务
 */
BaseType_t xTaskPriorityInherit(TaskHandle_t const pxMutexHolder)
{
    TCB_t * const pxMutexHolderTCB = pxMutexHolder;
    BaseType_t xReturn = pdFALSE;
    /**
     * If the mutex was given back by an interrupt while the queue was
     * locked then the mutex holder might now be NULL.  _RB_ Is this still
     * needed as interrupts can no longer use mutexes?
     */
    if (pxMutexHolder != NULL)
    {
        /**
         * If the holder of the mutex has a priority below the priority of
         * the task attempting to obtain the mutex then it will temporarily
         * inherit the priority of the task attempting to obtain the mutex.
         * 出现高优先级任务尝试获取已经被低优先级任务持有的互斥锁
         */
        if (pxMutexHolderTCB->uxPriority < pxCurrentTCB->uxPriority)
        {
            /**
             * Adjust the mutex holder state to account for its new
             * priority.  Only reset the event list item value if the value is
             * not being used for anything else.
             */
            if ((listGET_LIST_ITEM_VALUE(&(pxMutexHolderTCB->xEventListItem)) & taskEVENT_LIST_ITEM_VALUE_IN_USE) == 0UL)
            {
                /* 临时提高持有互斥锁的低优先任务的优先级,这样在加入就绪队列的时候，处于队列的前面 */
                listSET_LIST_ITEM_VALUE(&(pxMutexHolderTCB->xEventListItem),
                                (TickType_t)configMAX_PRIORITIES - (TickType_t)pxCurrentTCB->uxPriority);
            }
            /* If the task being modified is in the ready state it will need
             * to be moved into a new list.
             * 低优先级的任务，已经准备要开始运行
             */
            if (listIS_CONTAINED_WITHIN(&(pxReadyTasksLists[pxMutexHolderTCB->uxPriority]),
                                &(pxMutexHolderTCB->xStateListItem)) != pdFALSE)
            {
                if (uxListRemove(&(pxMutexHolderTCB->xStateListItem)) == (UBaseType_t)0)
                {
                    /* It is known that the task is in its ready list so
                     * there is no need to check again and the port level
                     * reset macro can be called directly. */
                    portRESET_READY_PRIORITY(pxMutexHolderTCB->uxPriority, uxTopReadyPriority);
                }
                /**
                 * Inherit the priority before being moved into the new list.
                 * 提高低优先级任务的优先级
                 */
                pxMutexHolderTCB->uxPriority = pxCurrentTCB->uxPriority;
                prvAddTaskToReadyList(pxMutexHolderTCB);
            }
            else
            {
                /**
                 * Just inherit the priority.
                 * 提高低优先级任务的优先级
                 */
                pxMutexHolderTCB->uxPriority = pxCurrentTCB->uxPriority;
            }
            traceTASK_PRIORITY_INHERIT(pxMutexHolderTCB, pxCurrentTCB->uxPriority);
            /**
             * Inheritance occurred.
             * 出现优先级继承
             */
            xReturn = pdTRUE;
        }
        else
        {
            if (pxMutexHolderTCB->uxBasePriority < pxCurrentTCB->uxPriority)
            {
                /* The base priority of the mutex holder is lower than the
                 * priority of the task attempting to take the mutex, but the
                 * current priority of the mutex holder is not lower than the
                 * priority of the task attempting to take the mutex.
                 * Therefore the mutex holder must have already inherited a
                 * priority, but inheritance would have occurred if that had
                 * not been the case. */
                xReturn = pdTRUE;
            }
        }
    }
    return xReturn;
}


BaseType_t xTaskPriorityDisinherit(TaskHandle_t const pxMutexHolder)
{
    TCB_t * const pxTCB = pxMutexHolder;
    BaseType_t xReturn = pdFALSE;
    if (pxMutexHolder != NULL)
    {
        /* A task can only have an inherited priority if it holds the mutex.
         * If the mutex is held by a task then it cannot be given from an
         * interrupt, and if a mutex is given by the holding task then it must
         * be the running state task. */
        configASSERT(pxTCB == pxCurrentTCB);
        configASSERT(pxTCB->uxMutexesHeld);
        (pxTCB->uxMutexesHeld)--;
        /* Has the holder of the mutex inherited the priority of another
         * task? */
        if (pxTCB->uxPriority != pxTCB->uxBasePriority)
        {
            /* Only disinherit if no other mutexes are held. */
            if (pxTCB->uxMutexesHeld == (UBaseType_t)0)
            {
                /* A task can only have an inherited priority if it holds
                 * the mutex.  If the mutex is held by a task then it cannot be
                 * given from an interrupt, and if a mutex is given by the
                 * holding task then it must be the running state task.  Remove
                 * the holding task from the ready list. */
                if (uxListRemove(&(pxTCB->xStateListItem)) == (UBaseType_t)0)
                {
                    portRESET_READY_PRIORITY(pxTCB->uxPriority, uxTopReadyPriority);
                }
                /* Disinherit the priority before adding the task into the
                 * new  ready list. */
                traceTASK_PRIORITY_DISINHERIT(pxTCB, pxTCB->uxBasePriority);
                pxTCB->uxPriority = pxTCB->uxBasePriority;
                /* Reset the event list item value.  It cannot be in use for
                 * any other purpose if this task is running, and it must be
                 * running to give back the mutex. */
                listSET_LIST_ITEM_VALUE(&(pxTCB->xEventListItem),
                            (TickType_t)configMAX_PRIORITIES - (TickType_t)pxTCB->uxPriority);
                prvAddTaskToReadyList(pxTCB);
                /* Return true to indicate that a context switch is required.
                 * This is only actually required in the corner case whereby
                 * multiple mutexes were held and the mutexes were given back
                 * in an order different to that in which they were taken.
                 * If a context switch did not occur when the first mutex was
                 * returned, even if a task was waiting on it, then a context
                 * switch should occur when the last mutex is returned whether
                 * a task is waiting on it or not. */
                xReturn = pdTRUE;
            }
        }
    }
    return xReturn;
}

/**
 * @pxMutexHolder: 互斥锁的持有者
 * @uxHighestPriorityWaitingTask: 等待互斥锁的最高优先级的任务
 */
void vTaskPriorityDisinheritAfterTimeout(TaskHandle_t const pxMutexHolder,
                                          UBaseType_t uxHighestPriorityWaitingTask)
{
    TCB_t * const pxTCB = pxMutexHolder;
    UBaseType_t uxPriorityUsedOnEntry, uxPriorityToUse;
    const UBaseType_t uxOnlyOneMutexHeld = (UBaseType_t)1;
    if (pxMutexHolder != NULL)
    {
        /* If pxMutexHolder is not NULL then the holder must hold at least
         * one mutex. */
        configASSERT(pxTCB->uxMutexesHeld);
        /* Determine the priority to which the priority of the task that
         * holds the mutex should be set.  This will be the greater of the
         * holding task's base priority and the priority of the highest
         * priority task that is waiting to obtain the mutex. */
        if (pxTCB->uxBasePriority < uxHighestPriorityWaitingTask)
        {
            uxPriorityToUse = uxHighestPriorityWaitingTask;
        }
        else
        {
            uxPriorityToUse = pxTCB->uxBasePriority;
        }
        /* Does the priority need to change? */
        if (pxTCB->uxPriority != uxPriorityToUse)
        {
            /* Only disinherit if no other mutexes are held.  This is a
             * simplification in the priority inheritance implementation.  If
             * the task that holds the mutex is also holding other mutexes then
             * the other mutexes may have caused the priority inheritance. */
            if (pxTCB->uxMutexesHeld == uxOnlyOneMutexHeld)
            {
                /* If a task has timed out because it already holds the
                 * mutex it was trying to obtain then it cannot of inherited
                 * its own priority. */
                configASSERT(pxTCB != pxCurrentTCB);
                /* Disinherit the priority, remembering the previous
                 * priority to facilitate determining the subject task's
                 * state. */
                traceTASK_PRIORITY_DISINHERIT(pxTCB, uxPriorityToUse);
                uxPriorityUsedOnEntry = pxTCB->uxPriority;
                /* 临时调高持有互斥锁任务的优先级 */
                pxTCB->uxPriority = uxPriorityToUse;
                /* Only reset the event list item value if the value is not
                 * being used for anything else. */
                if ((listGET_LIST_ITEM_VALUE(&(pxTCB->xEventListItem)) & taskEVENT_LIST_ITEM_VALUE_IN_USE) == 0UL)
                {
                    listSET_LIST_ITEM_VALUE(&(pxTCB->xEventListItem), (TickType_t) configMAX_PRIORITIES - (TickType_t) uxPriorityToUse);
                }
                /* If the running task is not the task that holds the mutex
                 * then the task that holds the mutex could be in either the
                 * Ready, Blocked or Suspended states.  Only remove the task
                 * from its current state list if it is in the Ready state as
                 * the task's priority is going to change and there is one
                 * Ready list per priority. */
                if (listIS_CONTAINED_WITHIN(&(pxReadyTasksLists[uxPriorityUsedOnEntry]), &(pxTCB->xStateListItem)) != pdFALSE)
                {
                    if (uxListRemove(&(pxTCB->xStateListItem)) == (UBaseType_t)0)
                    {
                        /* It is known that the task is in its ready list so
                         * there is no need to check again and the port level
                         * reset macro can be called directly. */
                        portRESET_READY_PRIORITY(pxTCB->uxPriority, uxTopReadyPriority);
                    }
                    prvAddTaskToReadyList(pxTCB);
                }
            }
        }
    }
}

#endif

#if (portCRITICAL_NESTING_IN_TCB == 1)

    void vTaskEnterCritical(void)
    {
        portDISABLE_INTERRUPTS();

        if (xSchedulerRunning != pdFALSE)
        {
            (pxCurrentTCB->uxCriticalNesting)++;

            /* This is not the interrupt safe version of the enter critical
             * function so  assert() if it is being called from an interrupt
             * context.  Only API functions that end in "FromISR" can be used in an
             * interrupt.  Only assert if the critical nesting count is 1 to
             * protect against recursive calls if the assert function also uses a
             * critical section. */
            if (pxCurrentTCB->uxCriticalNesting == 1)
            {
                portASSERT_IF_IN_ISR();
            }
        }
    }

#endif /* portCRITICAL_NESTING_IN_TCB */


#if (portCRITICAL_NESTING_IN_TCB == 1)

void vTaskExitCritical(void)
{
    if (xSchedulerRunning != pdFALSE)
    {
        if (pxCurrentTCB->uxCriticalNesting > 0U)
        {
            (pxCurrentTCB->uxCriticalNesting)--;
            if (pxCurrentTCB->uxCriticalNesting == 0U)
            {
                portENABLE_INTERRUPTS();
            }
        }
    }
}

#endif /* portCRITICAL_NESTING_IN_TCB */


#if (configUSE_STATS_FORMATTING_FUNCTIONS > 0)

static char * prvWriteNameToBuffer(char * pcBuffer, const char * pcTaskName)
{
    size_t x;
    /* Start by copying the entire string. */
    strcpy(pcBuffer, pcTaskName);
    /* Pad the end of the string with spaces to ensure columns line up when
     * printed out. */
    for (x = strlen(pcBuffer); x < (size_t) (configMAX_TASK_NAME_LEN - 1); x++)
    {
        pcBuffer[x] = ' ';
    }
    /* Terminate. */
    pcBuffer[x] = (char) 0x00;
    /* Return the new end of string. */
    return &(pcBuffer[x]);
}

#endif /* (configUSE_STATS_FORMATTING_FUNCTIONS > 0) */


#if ((configUSE_TRACE_FACILITY == 1) && (configUSE_STATS_FORMATTING_FUNCTIONS > 0))

    void vTaskList(char * pcWriteBuffer)
    {
        TaskStatus_t * pxTaskStatusArray;
        UBaseType_t uxArraySize, x;
        char cStatus;

        /*
         * PLEASE NOTE:
         *
         * This function is provided for convenience only, and is used by many
         * of the demo applications.  Do not consider it to be part of the
         * scheduler.
         *
         * vTaskList() calls uxTaskGetSystemState(), then formats part of the
         * uxTaskGetSystemState() output into a human readable table that
         * displays task: names, states, priority, stack usage and task number.
         * Stack usage specified as the number of unused StackType_t words stack can hold
         * on top of stack - not the number of bytes.
         *
         * vTaskList() has a dependency on the sprintf() C library function that
         * might bloat the code size, use a lot of stack, and provide different
         * results on different platforms.  An alternative, tiny, third party,
         * and limited functionality implementation of sprintf() is provided in
         * many of the FreeRTOS/Demo sub-directories in a file called
         * printf-stdarg.c (note printf-stdarg.c does not provide a full
         * snprintf() implementation!).
         *
         * It is recommended that production systems call uxTaskGetSystemState()
         * directly to get access to raw stats data, rather than indirectly
         * through a call to vTaskList().
         */


        /* Make sure the write buffer does not contain a string. */
        *pcWriteBuffer = (char) 0x00;

        /* Take a snapshot of the number of tasks in case it changes while this
         * function is executing. */
        uxArraySize = uxCurrentNumberOfTasks;

        pxTaskStatusArray = pvPortMalloc(uxCurrentNumberOfTasks*sizeof(TaskStatus_t));

        if (pxTaskStatusArray != NULL)
        {
            /* Generate the (binary) data. */
            uxArraySize = uxTaskGetSystemState(pxTaskStatusArray, uxArraySize, NULL);

            /* Create a human readable table from the binary data. */
            for (x = 0; x < uxArraySize; x++)
            {
                switch(pxTaskStatusArray[x].eCurrentState)
                {
                    case eRunning:
                        cStatus = tskRUNNING_CHAR;
                        break;

                    case eReady:
                        cStatus = tskREADY_CHAR;
                        break;

                    case eBlocked:
                        cStatus = tskBLOCKED_CHAR;
                        break;

                    case eSuspended:
                        cStatus = tskSUSPENDED_CHAR;
                        break;

                    case eDeleted:
                        cStatus = tskDELETED_CHAR;
                        break;

                    case eInvalid: /* Fall through. */
                    default:       /* Should not get here, but it is included
                                    * to prevent static checking errors. */
                        cStatus = (char) 0x00;
                        break;
                }

                /* Write the task name to the string, padding with spaces so it
                 * can be printed in tabular form more easily. */
                pcWriteBuffer = prvWriteNameToBuffer(pcWriteBuffer, pxTaskStatusArray[x].pcTaskName);

                /* Write the rest of the string. */
                sprintf(pcWriteBuffer, "\t%c\t%u\t%u\t%u\r\n",
                        cStatus,
                        (unsigned int)pxTaskStatusArray[x].uxCurrentPriority,
                        (unsigned int)pxTaskStatusArray[x].usStackHighWaterMark,
                        (unsigned int)pxTaskStatusArray[x].xTaskNumber);
                pcWriteBuffer += strlen(pcWriteBuffer);
            }

            vPortFree(pxTaskStatusArray);
        }
    }

#endif /* ((configUSE_TRACE_FACILITY == 1) && (configUSE_STATS_FORMATTING_FUNCTIONS > 0)) */

#if ((configGENERATE_RUN_TIME_STATS == 1) && (configUSE_STATS_FORMATTING_FUNCTIONS > 0) && (configUSE_TRACE_FACILITY == 1))

void vTaskGetRunTimeStats(char * pcWriteBuffer)
{
    TaskStatus_t * pxTaskStatusArray;
    UBaseType_t uxArraySize, x;
    configRUN_TIME_COUNTER_TYPE ulTotalTime, ulStatsAsPercentage;
    /*
     * PLEASE NOTE:
     *
     * This function is provided for convenience only, and is used by many
     * of the demo applications.  Do not consider it to be part of the
     * scheduler.
     *
     * vTaskGetRunTimeStats() calls uxTaskGetSystemState(), then formats part
     * of the uxTaskGetSystemState() output into a human readable table that
     * displays the amount of time each task has spent in the Running state
     * in both absolute and percentage terms.
     *
     * vTaskGetRunTimeStats() has a dependency on the sprintf() C library
     * function that might bloat the code size, use a lot of stack, and
     * provide different results on different platforms.  An alternative,
     * tiny, third party, and limited functionality implementation of
     * sprintf() is provided in many of the FreeRTOS/Demo sub-directories in
     * a file called printf-stdarg.c (note printf-stdarg.c does not provide
     * a full snprintf() implementation!).
     *
     * It is recommended that production systems call uxTaskGetSystemState()
     * directly to get access to raw stats data, rather than indirectly
     * through a call to vTaskGetRunTimeStats().
     */
    /* Make sure the write buffer does not contain a string. */
    *pcWriteBuffer = (char) 0x00;
    /* Take a snapshot of the number of tasks in case it changes while this
     * function is executing. */
    uxArraySize = uxCurrentNumberOfTasks;
    pxTaskStatusArray = pvPortMalloc(uxCurrentNumberOfTasks * sizeof(TaskStatus_t));
    if (pxTaskStatusArray != NULL)
    {
        /* Generate the (binary) data. */
        uxArraySize = uxTaskGetSystemState(pxTaskStatusArray, uxArraySize, &ulTotalTime);
        /* For percentage calculations. */
        ulTotalTime /= 100UL;
        /* Avoid divide by zero errors. */
        if (ulTotalTime > 0UL)
        {
            /* Create a human readable table from the binary data. */
            for (x = 0; x < uxArraySize; x++)
            {
                /* What percentage of the total run time has the task used?
                 * This will always be rounded down to the nearest integer.
                 * ulTotalRunTime has already been divided by 100. */
                ulStatsAsPercentage = pxTaskStatusArray[x].ulRunTimeCounter / ulTotalTime;
                /* Write the task name to the string, padding with
                 * spaces so it can be printed in tabular form more
                 * easily. */
                pcWriteBuffer = prvWriteNameToBuffer(pcWriteBuffer, pxTaskStatusArray[x].pcTaskName);
                if (ulStatsAsPercentage > 0UL)
                {
                    #ifdef portLU_PRINTF_SPECIFIER_REQUIRED
                    {
                        sprintf(pcWriteBuffer, "\t%lu\t\t%lu%%\r\n",
                            pxTaskStatusArray[x].ulRunTimeCounter, ulStatsAsPercentage);
                    }
                    #else
                    {
                        /* sizeof(int) == sizeof(long) so a smaller
                         * printf() library can be used. */
                        sprintf(pcWriteBuffer, "\t%u\t\t%u%%\r\n",
                            (unsigned int)pxTaskStatusArray[x].ulRunTimeCounter, (unsigned int)ulStatsAsPercentage);
                    }
                    #endif
                }
                else
                {
                    /* If the percentage is zero here then the task has
                     * consumed less than 1% of the total run time. */
                    #ifdef portLU_PRINTF_SPECIFIER_REQUIRED
                    {
                        sprintf(pcWriteBuffer, "\t%lu\t\t<1%%\r\n", pxTaskStatusArray[x].ulRunTimeCounter);
                    }
                    #else
                    {
                        /* sizeof(int) == sizeof(long) so a smaller
                         * printf() library can be used. */
                        sprintf(pcWriteBuffer, "\t%u\t\t<1%%\r\n",
                            (unsigned int)pxTaskStatusArray[x].ulRunTimeCounter);
                    }
                    #endif
                }
                pcWriteBuffer += strlen(pcWriteBuffer);
            }
        }
        vPortFree(pxTaskStatusArray);
    }
}

#endif /* ((configGENERATE_RUN_TIME_STATS == 1) && (configUSE_STATS_FORMATTING_FUNCTIONS > 0)) */

TickType_t uxTaskResetEventItemValue(void)
{
    TickType_t uxReturn;
    TickType_t uxValue;

    uxReturn = listGET_LIST_ITEM_VALUE(&(pxCurrentTCB->xEventListItem));

    /* Reset the event list item to its normal value - so it can be used with
     * queues and semaphores. */
    uxValue = (TickType_t)configMAX_PRIORITIES - (TickType_t)pxCurrentTCB->uxPriority;
    listSET_LIST_ITEM_VALUE(&(pxCurrentTCB->xEventListItem), uxValue);

    return uxReturn;
}

#if (configUSE_MUTEXES == 1)

TaskHandle_t pvTaskIncrementMutexHeldCount(void)
{
    /* If xSemaphoreCreateMutex() is called before any tasks have been created
     * then pxCurrentTCB will be NULL. */
    if (pxCurrentTCB != NULL)
    {
        (pxCurrentTCB->uxMutexesHeld)++;
    }
    return pxCurrentTCB;
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

uint32_t ulTaskGenericNotifyTake(UBaseType_t uxIndexToWait,
                                  BaseType_t xClearCountOnExit,
                                  TickType_t xTicksToWait)
{
    uint32_t ulReturn;
    configASSERT(uxIndexToWait < configTASK_NOTIFICATION_ARRAY_ENTRIES);
    taskENTER_CRITICAL();
    {
        /* Only block if the notification count is not already non-zero. */
        if (pxCurrentTCB->ulNotifiedValue[uxIndexToWait] == 0UL)
        {
            /* Mark this task as waiting for a notification. */
            pxCurrentTCB->ucNotifyState[uxIndexToWait] = taskWAITING_NOTIFICATION;
            if (xTicksToWait > (TickType_t) 0)
            {
                prvAddCurrentTaskToDelayedList(xTicksToWait, pdTRUE);
                traceTASK_NOTIFY_TAKE_BLOCK(uxIndexToWait);
                /* All ports are written to allow a yield in a critical
                 * section (some will yield immediately, others wait until the
                 * critical section exits) - but it is not something that
                 * application code should ever do. */
                portYIELD_WITHIN_API();
            }
        }
    }
    taskEXIT_CRITICAL();
    taskENTER_CRITICAL();
    {
        traceTASK_NOTIFY_TAKE(uxIndexToWait);
        ulReturn = pxCurrentTCB->ulNotifiedValue[uxIndexToWait];
        if (ulReturn != 0UL)
        {
            if (xClearCountOnExit != pdFALSE)
            {
                pxCurrentTCB->ulNotifiedValue[uxIndexToWait] = 0UL;
            }
            else
            {
                pxCurrentTCB->ulNotifiedValue[uxIndexToWait] = ulReturn - (uint32_t) 1;
            }
        }
        pxCurrentTCB->ucNotifyState[uxIndexToWait] = taskNOT_WAITING_NOTIFICATION;
    }
    taskEXIT_CRITICAL();
    return ulReturn;
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

BaseType_t xTaskGenericNotifyWait(UBaseType_t uxIndexToWait,
                                   uint32_t ulBitsToClearOnEntry,
                                   uint32_t ulBitsToClearOnExit,
                                   uint32_t * pulNotificationValue,
                                   TickType_t xTicksToWait)
{
    BaseType_t xReturn;
    configASSERT(uxIndexToWait < configTASK_NOTIFICATION_ARRAY_ENTRIES);
    taskENTER_CRITICAL();
    {
        /**
         * Only block if a notification is not already pending.
         * 没有接收到通知
         */
        if (pxCurrentTCB->ucNotifyState[uxIndexToWait] != taskNOTIFICATION_RECEIVED)
        {
            /* Clear bits in the task's notification value as bits may get
             * set  by the notifying task or interrupt.  This can be used to
             * clear the value to zero. */
            pxCurrentTCB->ulNotifiedValue[uxIndexToWait] &= ~ulBitsToClearOnEntry;
            /* Mark this task as waiting for a notification. */
            pxCurrentTCB->ucNotifyState[uxIndexToWait] = taskWAITING_NOTIFICATION;
            /* 加入延迟等待队列 */
            if (xTicksToWait > (TickType_t)0)
            {
                prvAddCurrentTaskToDelayedList(xTicksToWait, pdTRUE);
                traceTASK_NOTIFY_WAIT_BLOCK(uxIndexToWait);
                /* All ports are written to allow a yield in a critical
                 * section (some will yield immediately, others wait until the
                 * critical section exits) - but it is not something that
                 * application code should ever do.
                 * 触发任务调度
                 */
                portYIELD_WITHIN_API();
            }
        }
    }
    taskEXIT_CRITICAL();

    /* 接收到了任务通知事件或者发生超时，任务恢复执行 */
    taskENTER_CRITICAL();
    {
        traceTASK_NOTIFY_WAIT(uxIndexToWait);
        if (pulNotificationValue != NULL)
        {
            /* Output the current notification value, which may or may not
             * have changed. */
            *pulNotificationValue = pxCurrentTCB->ulNotifiedValue[uxIndexToWait];
        }
        /* If ucNotifyValue is set then either the task never entered the
         * blocked state (because a notification was already pending) or the
         * task unblocked because of a notification.  Otherwise the task
         * unblocked because of a timeout. */
        if (pxCurrentTCB->ucNotifyState[uxIndexToWait] != taskNOTIFICATION_RECEIVED)
        {
            /**
             * A notification was not received.
             * 等待超时
             */
            xReturn = pdFALSE;
        }
        else
        {
            /* A notification was already pending or a notification was
             * received while the task was waiting.
             * 接收到任务通知
            */
            pxCurrentTCB->ulNotifiedValue[uxIndexToWait] &= ~ulBitsToClearOnExit;
            xReturn = pdTRUE;
        }
        pxCurrentTCB->ucNotifyState[uxIndexToWait] = taskNOT_WAITING_NOTIFICATION;
    }

    taskEXIT_CRITICAL();

    return xReturn;
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

/**
 * @xTaskToNotify:  给接收任务通知的task发送任务通知信息
 * @ulValue:        通知值
 * @eAction:        更新值的方式
 */
BaseType_t xTaskGenericNotify(TaskHandle_t xTaskToNotify,
                               UBaseType_t uxIndexToNotify,
                               uint32_t ulValue,
                               eNotifyAction eAction,
                               uint32_t * pulPreviousNotificationValue)
{
    TCB_t * pxTCB;
    BaseType_t xReturn = pdPASS;
    uint8_t ucOriginalNotifyState;
    configASSERT(uxIndexToNotify < configTASK_NOTIFICATION_ARRAY_ENTRIES);
    configASSERT(xTaskToNotify);
    pxTCB = xTaskToNotify;
    taskENTER_CRITICAL();
    {
        if (pulPreviousNotificationValue != NULL)
        {
            *pulPreviousNotificationValue = pxTCB->ulNotifiedValue[uxIndexToNotify];
        }
        ucOriginalNotifyState = pxTCB->ucNotifyState[uxIndexToNotify];
        pxTCB->ucNotifyState[uxIndexToNotify] = taskNOTIFICATION_RECEIVED;
        switch(eAction)
        {
            case eSetBits:
                pxTCB->ulNotifiedValue[uxIndexToNotify] |= ulValue;
                break;
            case eIncrement:
                (pxTCB->ulNotifiedValue[uxIndexToNotify])++;
                break;
            case eSetValueWithOverwrite:
                pxTCB->ulNotifiedValue[uxIndexToNotify] = ulValue;
                break;
            case eSetValueWithoutOverwrite:
                if (ucOriginalNotifyState != taskNOTIFICATION_RECEIVED)
                {
                    pxTCB->ulNotifiedValue[uxIndexToNotify] = ulValue;
                }
                else
                {
                    /* The value could not be written to the task. */
                    xReturn = pdFAIL;
                }
                break;
            case eNoAction:
                /* The task is being notified without its notify value being
                 * updated. */
                break;
            default:
                /* Should not get here if all enums are handled.
                 * Artificially force an assert by testing a value the
                 * compiler can't assume is const. */
                configASSERT(xTickCount == (TickType_t) 0);
                break;
        }
        traceTASK_NOTIFY(uxIndexToNotify);
        /**
         * If the task is in the blocked state specifically to wait for a
         * notification then unblock it now.
         * 任务阻塞等待接收通知
         */
        if (ucOriginalNotifyState == taskWAITING_NOTIFICATION)
        {
            listREMOVE_ITEM(&(pxTCB->xStateListItem));
            prvAddTaskToReadyList(pxTCB);
            /* The task should not have been on an event list. */
            configASSERT(listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) == NULL);
            #if (configUSE_TICKLESS_IDLE != 0)
            {
                /* If a task is blocked waiting for a notification then
                 * xNextTaskUnblockTime might be set to the blocked task's time
                 * out time.  If the task is unblocked for a reason other than
                 * a timeout xNextTaskUnblockTime is normally left unchanged,
                 * because it will automatically get reset to a new value when
                 * the tick count equals xNextTaskUnblockTime.  However if
                 * tickless idling is used it might be more important to enter
                 * sleep mode at the earliest possible time - so reset
                 * xNextTaskUnblockTime here to ensure it is updated at the
                 * earliest possible time. */
                prvResetNextTaskUnblockTime();
            }
            #endif
            if (pxTCB->uxPriority > pxCurrentTCB->uxPriority)
            {
                /* The notified task has a priority above the currently
                 * executing task so a yield is required. */
                taskYIELD_IF_USING_PREEMPTION();
            }
        }
    }
    taskEXIT_CRITICAL();

    return xReturn;
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

BaseType_t xTaskGenericNotifyFromISR(TaskHandle_t xTaskToNotify,
                                      UBaseType_t uxIndexToNotify,
                                      uint32_t ulValue,
                                      eNotifyAction eAction,
                                      uint32_t * pulPreviousNotificationValue,
                                      BaseType_t * pxHigherPriorityTaskWoken)
{
    TCB_t * pxTCB;
    uint8_t ucOriginalNotifyState;
    BaseType_t xReturn = pdPASS;
    UBaseType_t uxSavedInterruptStatus;
    configASSERT(xTaskToNotify);
    configASSERT(uxIndexToNotify < configTASK_NOTIFICATION_ARRAY_ENTRIES);
    /* RTOS ports that support interrupt nesting have the concept of a
     * maximum  system call (or maximum API call) interrupt priority.
     * Interrupts that are  above the maximum system call priority are keep
     * permanently enabled, even when the RTOS kernel is in a critical section,
     * but cannot make any calls to FreeRTOS API functions.  If configASSERT()
     * is defined in FreeRTOSConfig.h then
     * portASSERT_IF_INTERRUPT_PRIORITY_INVALID() will result in an assertion
     * failure if a FreeRTOS API function is called from an interrupt that has
     * been assigned a priority above the configured maximum system call
     * priority.  Only FreeRTOS functions that end in FromISR can be called
     * from interrupts  that have been assigned a priority at or (logically)
     * below the maximum system call interrupt priority.  FreeRTOS maintains a
     * separate interrupt safe API to ensure interrupt entry is as fast and as
     * simple as possible.  More information (albeit Cortex-M specific) is
     * provided on the following link:
     * https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
    portASSERT_IF_INTERRUPT_PRIORITY_INVALID();
    pxTCB = xTaskToNotify;
    uxSavedInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
    {
        if (pulPreviousNotificationValue != NULL)
        {
            *pulPreviousNotificationValue = pxTCB->ulNotifiedValue[uxIndexToNotify];
        }
        ucOriginalNotifyState = pxTCB->ucNotifyState[uxIndexToNotify];
        pxTCB->ucNotifyState[uxIndexToNotify] = taskNOTIFICATION_RECEIVED;
        switch(eAction)
        {
            case eSetBits:
                pxTCB->ulNotifiedValue[uxIndexToNotify] |= ulValue;
                break;
            case eIncrement:
                (pxTCB->ulNotifiedValue[uxIndexToNotify])++;
                break;
            case eSetValueWithOverwrite:
                pxTCB->ulNotifiedValue[uxIndexToNotify] = ulValue;
                break;
            case eSetValueWithoutOverwrite:
                if (ucOriginalNotifyState != taskNOTIFICATION_RECEIVED)
                {
                    pxTCB->ulNotifiedValue[uxIndexToNotify] = ulValue;
                }
                else
                {
                    /* The value could not be written to the task. */
                    xReturn = pdFAIL;
                }
                break;
            case eNoAction:
                /* The task is being notified without its notify value being
                 * updated. */
                break;
            default:
                /* Should not get here if all enums are handled.
                 * Artificially force an assert by testing a value the
                 * compiler can't assume is const. */
                configASSERT(xTickCount == (TickType_t)0);
                break;
        }
        traceTASK_NOTIFY_FROM_ISR(uxIndexToNotify);
        /* If the task is in the blocked state specifically to wait for a
         * notification then unblock it now. */
        if (ucOriginalNotifyState == taskWAITING_NOTIFICATION)
        {
            /* The task should not have been on an event list. */
            configASSERT(listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) == NULL);
            if (uxSchedulerSuspended == (UBaseType_t) pdFALSE)
            {
                listREMOVE_ITEM(&(pxTCB->xStateListItem));
                prvAddTaskToReadyList(pxTCB);
            }
            else
            {
                /* The delayed and ready lists cannot be accessed, so hold
                 * this task pending until the scheduler is resumed. */
                listINSERT_END(&(xPendingReadyList), &(pxTCB->xEventListItem));
            }
            if (pxTCB->uxPriority > pxCurrentTCB->uxPriority)
            {
                /* The notified task has a priority above the currently
                 * executing task so a yield is required. */
                if (pxHigherPriorityTaskWoken != NULL)
                {
                    *pxHigherPriorityTaskWoken = pdTRUE;
                }
                /* Mark that a yield is pending in case the user is not
                 * using the "xHigherPriorityTaskWoken" parameter to an ISR
                 * safe FreeRTOS function. */
                xYieldPending = pdTRUE;
            }
        }
    }
    portCLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptStatus);

    return xReturn;
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

void vTaskGenericNotifyGiveFromISR(TaskHandle_t xTaskToNotify,
                                    UBaseType_t uxIndexToNotify,
                                    BaseType_t * pxHigherPriorityTaskWoken)
{
    TCB_t * pxTCB;
    uint8_t ucOriginalNotifyState;
    UBaseType_t uxSavedInterruptStatus;
    configASSERT(xTaskToNotify);
    configASSERT(uxIndexToNotify < configTASK_NOTIFICATION_ARRAY_ENTRIES);
    /* RTOS ports that support interrupt nesting have the concept of a
     * maximum  system call (or maximum API call) interrupt priority.
     * Interrupts that are  above the maximum system call priority are keep
     * permanently enabled, even when the RTOS kernel is in a critical section,
     * but cannot make any calls to FreeRTOS API functions.  If configASSERT()
     * is defined in FreeRTOSConfig.h then
     * portASSERT_IF_INTERRUPT_PRIORITY_INVALID() will result in an assertion
     * failure if a FreeRTOS API function is called from an interrupt that has
     * been assigned a priority above the configured maximum system call
     * priority.  Only FreeRTOS functions that end in FromISR can be called
     * from interrupts  that have been assigned a priority at or (logically)
     * below the maximum system call interrupt priority.  FreeRTOS maintains a
     * separate interrupt safe API to ensure interrupt entry is as fast and as
     * simple as possible.  More information (albeit Cortex-M specific) is
     * provided on the following link:
     * https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
    portASSERT_IF_INTERRUPT_PRIORITY_INVALID();
    pxTCB = xTaskToNotify;
    uxSavedInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
    {
        ucOriginalNotifyState = pxTCB->ucNotifyState[uxIndexToNotify];
        pxTCB->ucNotifyState[uxIndexToNotify] = taskNOTIFICATION_RECEIVED;
        /* 'Giving' is equivalent to incrementing a count in a counting
         * semaphore. */
        (pxTCB->ulNotifiedValue[uxIndexToNotify])++;
        traceTASK_NOTIFY_GIVE_FROM_ISR(uxIndexToNotify);
        /* If the task is in the blocked state specifically to wait for a
         * notification then unblock it now. */
        if (ucOriginalNotifyState == taskWAITING_NOTIFICATION)
        {
            /* The task should not have been on an event list. */
            configASSERT(listLIST_ITEM_CONTAINER(&(pxTCB->xEventListItem)) == NULL);
            if (uxSchedulerSuspended == (UBaseType_t)pdFALSE)
            {
                listREMOVE_ITEM(&(pxTCB->xStateListItem));
                prvAddTaskToReadyList(pxTCB);
            }
            else
            {
                /* The delayed and ready lists cannot be accessed, so hold
                 * this task pending until the scheduler is resumed. */
                listINSERT_END(&(xPendingReadyList), &(pxTCB->xEventListItem));
            }
            if (pxTCB->uxPriority > pxCurrentTCB->uxPriority)
            {
                /* The notified task has a priority above the currently
                 * executing task so a yield is required. */
                if (pxHigherPriorityTaskWoken != NULL)
                {
                    *pxHigherPriorityTaskWoken = pdTRUE;
                }
                /* Mark that a yield is pending in case the user is not
                 * using the "xHigherPriorityTaskWoken" parameter in an ISR
                 * safe FreeRTOS function. */
                xYieldPending = pdTRUE;
            }
        }
    }
    portCLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptStatus);
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

BaseType_t xTaskGenericNotifyStateClear(TaskHandle_t xTask,
                                         UBaseType_t uxIndexToClear)
{
    TCB_t * pxTCB;
    BaseType_t xReturn;
    configASSERT(uxIndexToClear < configTASK_NOTIFICATION_ARRAY_ENTRIES);
    /* If null is passed in here then it is the calling task that is having
     * its notification state cleared. */
    pxTCB = prvGetTCBFromHandle(xTask);
    taskENTER_CRITICAL();
    {
        if (pxTCB->ucNotifyState[uxIndexToClear] == taskNOTIFICATION_RECEIVED)
        {
            pxTCB->ucNotifyState[uxIndexToClear] = taskNOT_WAITING_NOTIFICATION;
            xReturn = pdPASS;
        }
        else
        {
            xReturn = pdFAIL;
        }
    }
    taskEXIT_CRITICAL();
    return xReturn;
}

#endif

#if (configUSE_TASK_NOTIFICATIONS == 1)

uint32_t ulTaskGenericNotifyValueClear(TaskHandle_t xTask,
                                        UBaseType_t uxIndexToClear,
                                        uint32_t ulBitsToClear)
{
    TCB_t * pxTCB;
    uint32_t ulReturn;
    /* If null is passed in here then it is the calling task that is having
     * its notification state cleared. */
    pxTCB = prvGetTCBFromHandle(xTask);
    taskENTER_CRITICAL();
    {
        /* Return the notification as it was before the bits were cleared,
         * then clear the bit mask. */
        ulReturn = pxTCB->ulNotifiedValue[uxIndexToClear];
        pxTCB->ulNotifiedValue[uxIndexToClear] &= ~ulBitsToClear;
    }
    taskEXIT_CRITICAL();
    return ulReturn;
}

#endif

#if ((configGENERATE_RUN_TIME_STATS == 1) && (INCLUDE_xTaskGetIdleTaskHandle == 1))

    configRUN_TIME_COUNTER_TYPE ulTaskGetIdleRunTimeCounter(void)
    {
        return xIdleTaskHandle->ulRunTimeCounter;
    }

#endif


#if ((configGENERATE_RUN_TIME_STATS == 1) && (INCLUDE_xTaskGetIdleTaskHandle == 1))

    configRUN_TIME_COUNTER_TYPE ulTaskGetIdleRunTimePercent(void)
    {
        configRUN_TIME_COUNTER_TYPE ulTotalTime, ulReturn;

        ulTotalTime = portGET_RUN_TIME_COUNTER_VALUE();

        /* For percentage calculations. */
        ulTotalTime /= (configRUN_TIME_COUNTER_TYPE) 100;

        /* Avoid divide by zero errors. */
        if (ulTotalTime > (configRUN_TIME_COUNTER_TYPE) 0)
        {
            ulReturn = xIdleTaskHandle->ulRunTimeCounter / ulTotalTime;
        }
        else
        {
            ulReturn = 0;
        }

        return ulReturn;
    }

#endif

static void prvAddCurrentTaskToDelayedList(TickType_t xTicksToWait,
                                            const BaseType_t xCanBlockIndefinitely)
{
    TickType_t xTimeToWake;
    const TickType_t xConstTickCount = xTickCount;

    #if (INCLUDE_xTaskAbortDelay == 1)
    {
        /* About to enter a delayed list, so ensure the ucDelayAborted flag is
         * reset to pdFALSE so it can be detected as having been set to pdTRUE
         * when the task leaves the Blocked state. */
        pxCurrentTCB->ucDelayAborted = pdFALSE;
    }
    #endif

    /**
     * Remove the task from the ready list before adding it to the blocked list
     * as the same list item is used for both lists.、
     * 当前任务从就绪队列删除
     */
    if (uxListRemove(&(pxCurrentTCB->xStateListItem)) == (UBaseType_t)0)
    {
        /**
         * The current task must be in a ready list, so there is no need to
         * check, and the port reset macro can be called directly.
         * 取消任务的uxTopReadyPriority标记
         */
        portRESET_READY_PRIORITY(pxCurrentTCB->uxPriority, uxTopReadyPriority);
    }

    #if (INCLUDE_vTaskSuspend == 1)
    {
        /* 无限等待 */
        if ((xTicksToWait == portMAX_DELAY) && (xCanBlockIndefinitely != pdFALSE))
        {
            /* Add the task to the suspended task list instead of a delayed task
             * list to ensure it is not woken by a timing event.  It will block
             * indefinitely.
             * 无限等待，直接加入到挂起队列
             */
            listINSERT_END(&xSuspendedTaskList, &(pxCurrentTCB->xStateListItem));
        }
        else
        {
            /* Calculate the time at which the task should be woken if the event
             * does not occur.  This may overflow but this doesn't matter, the
             * kernel will manage it correctly.
             * 计算任务绝对唤醒的时间点
             */
            xTimeToWake = xConstTickCount + xTicksToWait;

            /**
             * The list item will be inserted in wake time order.
             * 设置任务延迟超时时间
             */
            listSET_LIST_ITEM_VALUE(&(pxCurrentTCB->xStateListItem), xTimeToWake);

            /* 发生溢出 */
            if (xTimeToWake < xConstTickCount)
            {
                /**
                 * Wake time has overflowed.  Place this item in the overflow
                 * list
                 * 任务已经超时
                 */
                vListInsert(pxOverflowDelayedTaskList, &(pxCurrentTCB->xStateListItem));
            }
            else
            {
                /**
                 * The wake time has not overflowed, so the current block list
                 * is used.
                 */
                vListInsert(pxDelayedTaskList, &(pxCurrentTCB->xStateListItem));

                /* If the task entering the blocked state was placed at the
                 * head of the list of blocked tasks then xNextTaskUnblockTime
                 * needs to be updated too. */
                if (xTimeToWake < xNextTaskUnblockTime)
                {
                    /* 更新下一个取消任务阻塞的时间点 */
                    xNextTaskUnblockTime = xTimeToWake;
                }
            }
        }
    }
    #else /* INCLUDE_vTaskSuspend */
    {
        /* Calculate the time at which the task should be woken if the event
         * does not occur.  This may overflow but this doesn't matter, the kernel
         * will manage it correctly. */
        xTimeToWake = xConstTickCount + xTicksToWait;

        /* The list item will be inserted in wake time order. */
        listSET_LIST_ITEM_VALUE(&(pxCurrentTCB->xStateListItem), xTimeToWake);

        if (xTimeToWake < xConstTickCount)
        {
            /* Wake time has overflowed.  Place this item in the overflow list. */
            vListInsert(pxOverflowDelayedTaskList, &(pxCurrentTCB->xStateListItem));
        }
        else
        {
            /* The wake time has not overflowed, so the current block list is used. */
            vListInsert(pxDelayedTaskList, &(pxCurrentTCB->xStateListItem));

            /* If the task entering the blocked state was placed at the head of the
             * list of blocked tasks then xNextTaskUnblockTime needs to be updated
             * too. */
            if (xTimeToWake < xNextTaskUnblockTime)
            {
                xNextTaskUnblockTime = xTimeToWake;
            }
        }

        /* Avoid compiler warning when INCLUDE_vTaskSuspend is not 1. */
        (void) xCanBlockIndefinitely;
    }
    #endif
}