线程池的部分原理研究2

基于上一个博客的研究，接下来针对具体的代码进行分析。

程序设计流程：

线程池初始化(n个线程) ----> 往线程池仍任务(n个任务)  ----> 销毁线程池(n个线程)

    pool_init(int pnt)                   pool_add_worker                      pool_destroy()

                                 ( (void *(*process) (void *arg), void *arg))

 

分为以下的步骤去熟悉整体的代码和细节代码

1 其中先熟悉其主要结构体的成员

/*
    all tasks in the linked list 
    recalled function for task
*/
typedef struct worker
{
    void *(*process) (void *arg); /*recalled function*/
    void *arg;
    struct worker *next;
} CThread_worker;

typedef struct cthread_pool
{
    pthread_mutex_t queue_lock;
    pthread_cond_t queue_ready;
    /*head for task*/
    CThread_worker *queue_head;
    pthread_t *threadid;
    /*max number of pthread*/
    int max_thread_num;
    /*current queue number*/
    int cur_queue_size;
    /*whether to destroy pool*/
    int shutdown;
} CThread_pool;

2 pool_init(int max_thread_num)程序实现

pool_init(int max_thread_num)
{   int i;
    pool = (CThread_pool *) malloc (sizeof (CThread_pool));
    pthread_mutex_init (&(pool->queue_lock), NULL);
    pthread_cond_init (&(pool->queue_ready), NULL);
    pool->queue_head = NULL;
    pool->max_thread_num = max_thread_num;
    pool->cur_queue_size = 0;
    pool->shutdown = 0;
    pool->threadid = (pthread_t *) malloc (max_thread_num * sizeof (pthread_t));
    for (i = 0; i < max_thread_num; i++)
        pthread_create (&(pool->threadid[i]), NULL, thread_routine,NULL);
}

void * thread_routine (void *arg)
{
    printf ("starting thread 0x%lu\n", pthread_self ());
    while (1)
    {
        /*
            if the size of waiting list, do not destroy pool
            waiting to do
        */

        pthread_mutex_lock (&(pool->queue_lock));
        while (pool->cur_queue_size == 0 && !pool->shutdown)
        {
            printf ("thread 0x%lu is waiting\n", pthread_self ());
            pthread_cond_wait (&(pool->queue_ready), &(pool->queue_lock));
        }

        if (pool->shutdown)
        {
            pthread_mutex_unlock (&(pool->queue_lock));
            printf ("thread 0x%lu will exit\n", pthread_self ());
            pthread_exit (NULL);
        }
        printf ("thread 0x%lu is starting to work\n", pthread_self ());

        assert (pool->cur_queue_size != 0);
        assert (pool->queue_head != NULL);

        /*head - 1, fetch the head of linked list*/
        pool->cur_queue_size--;
        CThread_worker *worker = pool->queue_head;
        pool->queue_head = worker->next;
        pthread_mutex_unlock (&(pool->queue_lock));
        /*recalled function*/
        (*(worker->process)) (worker->arg);
        free (worker);
        worker = NULL;
    }
    pthread_exit (NULL);
}

cur_queue_size在仍任务时++，在创建线程时--，
并且 CThread_worker *worker = pool->queue_head,
xy(x == pool->queue_head)
pool->queue_head = worker->next  <====> pool->queue_head = pool->queue_head->next
y 增加一个y作为pool最新的链表头。
借助遍历链表说明以上情况：

while (h->next != NULL) {
        h = h->next;
        printf("%d  ", h->score);
}
abcdefghi 
a->head = a,
a->nex = b,c,d,e,f,g,h,i

3. 销毁线程链表

int pool_destroy ()
{
    int i;
    pool->shutdown = 1;

    /*ask all pthreads*/
    pthread_cond_broadcast (&(pool->queue_ready));

    for (i = 0; i < pool->max_thread_num; i++)
        pthread_join (pool->threadid[i], NULL);
    free (pool->threadid);

    /*destroy waiting list*/
    CThread_worker *head = NULL;
    while (pool->queue_head != NULL)
    {
        head = pool->queue_head;
        pool->queue_head = pool->queue_head->next;
        free (head);
        if (pool->queue_head == NULL)
            break;
    }
    /*lock free*/
    pthread_mutex_destroy(&(pool->queue_lock));
    pthread_cond_destroy(&(pool->queue_ready));

    free (pool);
    pool=NULL;
    return 0;
}

while (pool->queue_head != NULL)
    {
        head = pool->queue_head;
        pool->queue_head = pool->queue_head->next;
        free (head);
        if (pool->queue_head == NULL)
            break;
    }

pool : abcdefghi 

pool->queue_head = a

pool->queue_head->next = b c d e f g h i

附加链表的具体知识：

该线程池利用到了单链表结构，区分顺序表结构，因前者随机物理内存位置存储数据，后者顺序存储。