OpenHarmony内核源码分析 (静态分配篇) | 很简单的一位小朋友

typedef struct {//静态内存池信息结构体
    UINT32 uwBlkSize;           /**< Block size | 块大小*/
    UINT32 uwBlkNum;            /**< Block number | 块数量*/
    UINT32 uwBlkCnt;            /**< The number of allocated blocks | 已经被分配的块数量*/
    LOS_MEMBOX_NODE stFreeList; /**< Free list | 空闲链表*/
} LOS_MEMBOX_INFO;

typedef struct tagMEMBOX_NODE { //内存池中空闲节点的结构,是个单向的链表
    struct tagMEMBOX_NODE *pstNext; /**< Free node's pointer to the next node in a memory pool | 指向内存池中下一个空闲节点的指针*/
} LOS_MEMBOX_NODE;

`欢迎大家关注公众号<程序猿百晓生>，可以了解到以下知识点。`
1.OpenHarmony开发基础
2.OpenHarmony北向开发环境搭建
3.鸿蒙南向开发环境的搭建
4.鸿蒙生态应用开发白皮书V2.0 & V3.0
5.鸿蒙开发面试真题（含参考答案） 
6.TypeScript入门学习手册
7.OpenHarmony 经典面试题(含参考答案)
8.OpenHarmony设备开发入门【最新版】
9.沉浸式剖析OpenHarmony源代码
10.系统定制指南
11.【OpenHarmony】Uboot 驱动加载流程
12.OpenHarmony构建系统--GN与子系统、部件、模块详解
13.ohos开机init启动流程
14.鸿蒙版性能优化指南
.......

///初始化一个静态内存池，根据入参设定其起始地址、总大小及每个内存块大小
LITE_OS_SEC_TEXT_INIT UINT32 LOS_MemboxInit(VOID *pool, UINT32 poolSize, UINT32 blkSize)
{
    LOS_MEMBOX_INFO *boxInfo = (LOS_MEMBOX_INFO *)pool;//在内存起始处放置控制头
    LOS_MEMBOX_NODE *node = NULL;
    //...
    UINT32 index;
    UINT32 intSave;
    MEMBOX_LOCK(intSave);
    boxInfo->uwBlkSize = LOS_MEMBOX_ALIGNED(blkSize + OS_MEMBOX_NODE_HEAD_SIZE); //节块总大小(节头+节体)
    boxInfo->uwBlkNum = (poolSize - sizeof(LOS_MEMBOX_INFO)) / boxInfo->uwBlkSize;//总节块数量
    boxInfo->uwBlkCnt = 0;	//已分配的数量
    if (boxInfo->uwBlkNum == 0) {//只有0块的情况
        MEMBOX_UNLOCK(intSave);
        return LOS_NOK;
    }
    node = (LOS_MEMBOX_NODE *)(boxInfo + 1);//去除池头,找到第一个节块位置
    boxInfo->stFreeList.pstNext = node;//池头空闲链表指向第一个节块
    for (index = 0; index < boxInfo->uwBlkNum - 1; ++index) {//切割节块,挂入空闲链表
        node->pstNext = OS_MEMBOX_NEXT(node, boxInfo->uwBlkSize);//按块大小切割好,统一由pstNext指向
        node = node->pstNext;//node存储了下一个节点的地址信息
    }
    node->pstNext = NULL;//最后一个为null
    MEMBOX_UNLOCK(intSave);
    return LOS_OK;
}

///从指定的静态内存池中申请一块静态内存块,整个内核源码只有 OsSwtmrScan中用到了静态内存.
LITE_OS_SEC_TEXT VOID *LOS_MemboxAlloc(VOID *pool)
{
    LOS_MEMBOX_INFO *boxInfo = (LOS_MEMBOX_INFO *)pool;
    LOS_MEMBOX_NODE *node = NULL;
    LOS_MEMBOX_NODE *nodeTmp = NULL;
    UINT32 intSave;
    if (pool == NULL) {
        return NULL;
    }
    MEMBOX_LOCK(intSave);
    node = &(boxInfo->stFreeList);//拿到空闲单链表
    if (node->pstNext != NULL) {//不需要遍历链表,因为这是空闲链表
        nodeTmp = node->pstNext;//先记录要使用的节点
        node->pstNext = nodeTmp->pstNext;//不再空闲了,把节点摘出去了.
        OS_MEMBOX_SET_MAGIC(nodeTmp);//为已使用的节块设置魔法数字
        boxInfo->uwBlkCnt++;//已使用块数增加
    }
    MEMBOX_UNLOCK(intSave);
    return (nodeTmp == NULL) ? NULL : OS_MEMBOX_USER_ADDR(nodeTmp);//返回可用的虚拟地址
}

/// 释放指定的一块静态内存块
LITE_OS_SEC_TEXT UINT32 LOS_MemboxFree(VOID *pool, VOID *box)
{
    LOS_MEMBOX_INFO *boxInfo = (LOS_MEMBOX_INFO *)pool;
    UINT32 ret = LOS_NOK;
    UINT32 intSave;
    if ((pool == NULL) || (box == NULL)) {
        return LOS_NOK;
    }
    MEMBOX_LOCK(intSave);
    do {
        LOS_MEMBOX_NODE *node = OS_MEMBOX_NODE_ADDR(box);//通过节体获取节块首地址
        if (OsCheckBoxMem(boxInfo, node) != LOS_OK) {
            break;
        }
        node->pstNext = boxInfo->stFreeList.pstNext;//节块指向空闲链表表头
        boxInfo->stFreeList.pstNext = node;//空闲链表表头反指向它,意味节块排到第一,下次申请将首个分配它
        boxInfo->uwBlkCnt--;//已经使用的内存块减一
        ret = LOS_OK;
    } while (0);//将被编译时优化
    MEMBOX_UNLOCK(intSave);
    return ret;
}

///软时钟初始化 ,注意函数在多CPU情况下会执行多次
STATIC UINT32 SwtmrBaseInit(VOID)
{
    UINT32 ret;
    UINT32 size = sizeof(SWTMR_CTRL_S) * LOSCFG_BASE_CORE_SWTMR_LIMIT;
    SWTMR_CTRL_S *swtmr = (SWTMR_CTRL_S *)LOS_MemAlloc(m_aucSysMem0, size); /* system resident resource */
    if (swtmr == NULL) {
        return LOS_ERRNO_SWTMR_NO_MEMORY;
    }
    (VOID)memset_s(swtmr, size, 0, size);//清0
    g_swtmrCBArray = swtmr;//软时钟
    LOS_ListInit(&g_swtmrFreeList);//初始化空闲链表
    for (UINT16 index = 0; index < LOSCFG_BASE_CORE_SWTMR_LIMIT; index++, swtmr++) {
            swtmr->usTimerID = index;//按顺序赋值
            LOS_ListTailInsert(&g_swtmrFreeList, &swtmr->stSortList.sortLinkNode);//通过sortLinkNode将节点挂到空闲链表 
    }
	//想要用静态内存池管理,就必须要使用LOS_MEMBOX_SIZE来计算申请的内存大小,因为需要点前缀内存承载头部信息.
    size = LOS_MEMBOX_SIZE(sizeof(SwtmrHandlerItem), OS_SWTMR_HANDLE_QUEUE_SIZE);//规划一片内存区域作为软时钟处理函数的静态内存池。
    g_swtmrHandlerPool = (UINT8 *)LOS_MemAlloc(m_aucSysMem1, size); /* system resident resource */
    if (g_swtmrHandlerPool == NULL) {
        return LOS_ERRNO_SWTMR_NO_MEMORY;
    }
    ret = LOS_MemboxInit(g_swtmrHandlerPool, size, sizeof(SwtmrHandlerItem));
    if (ret != LOS_OK) {
        return LOS_ERRNO_SWTMR_HANDLER_POOL_NO_MEM;
    }
    for (UINT16 index = 0; index < LOSCFG_KERNEL_CORE_NUM; index++) {
        SwtmrRunQue *srq = &g_swtmrRunQue[index];
        /* The linked list of all cores must be initialized at core 0 startup for load balancing */
        OsSortLinkInit(&srq->swtmrSortLink);
        LOS_ListInit(&srq->swtmrHandlerQueue);
        srq->swtmrTask = NULL;
    }
    SwtmrDebugDataInit();
    return LOS_OK;
}

typedef VOID (*SWTMR_PROC_FUNC)(UINTPTR arg);	//函数指针, 赋值给 SWTMR_CTRL_S->pfnHandler,回调处理
typedef struct {//处理软件定时器超时的回调函数的结构体
    SWTMR_PROC_FUNC handler;    /**< Callback function that handles software timer timeout  */	//处理软件定时器超时的回调函数
    UINTPTR arg;                /**< Parameter passed in when the callback function
                                     that handles software timer timeout is called */	//调用处理软件计时器超时的回调函数时传入的参数
    LOS_DL_LIST node;
#ifdef LOSCFG_SWTMR_DEBUG
    UINT32 swtmrID;
#endif
} SwtmrHandlerItem;