线程池

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>
#include <assert.h>

/*
*线程池里所有运行和等待的任务都是一个CThread_worker
*由于所有任务都在链表里，所以是一个链表结构
*/
typedef struct worker
{
    /*回调函数，任务运行时会调用此函数，注意也可声明成其它形式*/
    void *(*process) (void *arg);
    void *arg;/*回调函数的参数*/
    struct worker *next;

} CThread_worker;

/*线程池结构*/
typedef struct
{
    pthread_mutex_t queue_lock;
    pthread_cond_t queue_ready;

    /*链表结构，线程池中所有等待任务*/
    CThread_worker *queue_head;

    /*是否销毁线程池*/
    int shutdown;
    pthread_t *threadid;
    /*线程池中允许的活动线程数目*/
    int max_thread_num;
    /*当前等待队列的任务数目*/
    int cur_queue_size;

} CThread_pool;   /*定义线程池*/

int pool_add_worker (void *(*process) (void *arg), void *arg);
void *thread_routine (void *arg);     /*routine：程序*/

static CThread_pool *pool = NULL;    /*声明 pool为线程池指针*/
void pool_init (int max_thread_num)   /*线程池初始化*/
{
    pool = (CThread_pool *) malloc (sizeof (CThread_pool));
    /*线程池pool，初始化互斥量*/
    pthread_mutex_init (&(pool->queue_lock), NULL);
    /*线程池pool，初始化条件变量*/
    pthread_cond_init (&(pool->queue_ready), NULL);
   /
    pool->queue_head = NULL;   		/*任务队列头*/

    pool->max_thread_num = max_thread_num;   /*最大线程数*/
    pool->cur_queue_size = 0;   	/*当前任务数*/

    pool->shutdown = 0;   /*是否销毁*/

    pool->threadid =
        (pthread_t *) malloc (max_thread_num * sizeof (pthread_t));   /*申请线程地址空间*/
    int i = 0;
    for (i = 0; i < max_thread_num; i++)
    {    					/*把线程全部创建出来*/
        pthread_create (&(pool->threadid[i]), NULL, thread_routine, NULL);
    }
}
/*向线程池中加入任务*/
int
pool_add_worker (void *(*process) (void *arg), void *arg)   /*线程添加*/
{
    /*构造一个新任务*/
    CThread_worker *newworker =
        (CThread_worker *) malloc (sizeof (CThread_worker));    /*将任务传递进来*/
    newworker->process = process;    /*任务函数*/
    newworker->arg = arg;            /*函数参数*/
    newworker->next = NULL;/*别忘置空*/

    pthread_mutex_lock (&(pool->queue_lock));   /*添加新任务时需要加锁，防止其他线程改变公用变量*/
    /*将任务加入到等待队列中*/
    CThread_worker *member = pool->queue_head;   /*任务队列传入*/
    if (member != NULL)   /*任务队列不为空*/
    {
        while (member->next != NULL)   	/*任务队列链表遍历到最后位置*/
            member = member->next;
        member->next = newworker;   	/*新任务添加到队列链表中*/
    }
    else   /*任务队列为空*/
    {
        pool->queue_head = newworker;   /*新任务添加到队首*/
    }

    assert (pool->queue_head != NULL);  /*任务添加过程结束后，任务队列仍为空，报错*/

    pool->cur_queue_size++;   	/*池内当前任务数+1*/
    pthread_mutex_unlock (&(pool->queue_lock));     /*解锁*/
    pthread_cond_signal (&(pool->queue_ready));/*每次等待队列中有任务加入，都会试图唤醒一个等待线程；如果所有线程都在忙碌，这句没有任何作用*/
    return 0;
}

/*销毁线程池，等待队列中的任务不会再被执行，但是正在运行的线程会一直
把任务运行完后再退出*/
int pool_destroy ()        /*线程池销毁*/
{
    if (pool->shutdown)
        return -1;/*防止两次调用*/
    pool->shutdown = 1;

    /*唤醒所有等待线程，线程池要销毁了*/
    pthread_cond_broadcast (&(pool->queue_ready));

    /*阻塞等待线程退出，否则就成僵尸了*/
    int i;
    for (i = 0; i < pool->max_thread_num; i++)
        pthread_join (pool->threadid[i], NULL);
    free (pool->threadid);   				/*释放每一个线程空间*/

    /*销毁等待队列*/
    CThread_worker *head = NULL;
    while (pool->queue_head != NULL)
    {
        head = pool->queue_head;
        pool->queue_head = pool->queue_head->next;
        free (head);   					/*释放任务队列空间*/
    }
    /*条件变量和互斥量也别忘了销毁*/
    pthread_mutex_destroy(&(pool->queue_lock));
    pthread_cond_destroy(&(pool->queue_ready));

    free (pool);   					/*释放线程池空间*/
    /*销毁后指针置空是个好习惯*/
    pool=NULL;
    return 0;
}
void * thread_routine (void *arg)       /*线程调用函数*/
{
    printf ("starting thread 0x%x
", pthread_self ());
    while (1)
    {
        pthread_mutex_lock (&(pool->queue_lock));
        /*如果等待队列为0并且不销毁线程池，则处于阻塞状态; 注意
        pthread_cond_wait是一个原子操作，等待前会解锁，唤醒后会加锁*/
        while (pool->cur_queue_size == 0 && !pool->shutdown)
        {
            printf ("thread 0x%x is waiting
", pthread_self ());
            pthread_cond_wait (&(pool->queue_ready), &(pool->queue_lock));/*如果暂时没有任务，阻塞在此处，等待唤醒，防止不停查询，浪费CPU*/
        }

        /*线程池要销毁了*/
        if (pool->shutdown)
        {
            /*遇到break,continue,return等跳转语句，千万不要忘记先解锁*/
            pthread_mutex_unlock (&(pool->queue_lock));
            printf ("thread 0x%x will exit
", pthread_self ());
            pthread_exit (NULL);
        }

        printf ("thread 0x%x is starting to work
", pthread_self ());

        /*assert是调试的好帮手*/
        assert (pool->cur_queue_size != 0);
        assert (pool->queue_head != NULL);

        /*等待队列长度减去1，并取出链表中的头元素*/
        pool->cur_queue_size--;
        CThread_worker *worker = pool->queue_head;   /*每次执行的都是任务队列中第一个任务*/
        pool->queue_head = worker->next;   		/*任务队列头下移一个*/
        pthread_mutex_unlock (&(pool->queue_lock));

        /*调用回调函数，执行任务*/
        (*(worker->process)) (worker->arg);   /*开始执行取出来的任务*/
        free (worker);
        worker = NULL;
    }
    /*这一句应该是不可达的*/
    pthread_exit (NULL);
}

void * myprocess (void *arg)   /*任务线程*/
{
    printf ("threadid is 0x%x, working on task %d
", pthread_self (),*(int *) arg);
    sleep (1);/*休息一秒，延长任务的执行时间*/
    return NULL;
}

int main (int argc, char **argv)
{
    pool_init (3);/*线程池中最多三个活动线程*/

    /*连续向池中投入10个任务*/
    int *workingnum = (int *) malloc (sizeof (int) * 10);       /*任务编号*/
    int i;
    for (i = 0; i < 10; i++)
    {
        workingnum[i] = i;
        pool_add_worker (myprocess, &workingnum[i]);    /*任务添加进等待队列*/
    }
    /*等待所有任务完成*/
    sleep (5);
    /*销毁线程池*/
    pool_destroy ();

    free (workingnum);
    return 0;

       [root@localhost code]# ./thread_pool

starting thread 0xb63bab70
thread 0xb63bab70 is starting to work
threadid is 0xb63bab70, working on task 0
starting thread 0xb6dbbb70
thread 0xb6dbbb70 is starting to work
threadid is 0xb6dbbb70, working on task 1
starting thread 0xb77bcb70
thread 0xb77bcb70 is starting to work
threadid is 0xb77bcb70, working on task 2
thread 0xb63bab70 is starting to work
threadid is 0xb63bab70, working on task 3
thread 0xb6dbbb70 is starting to work
threadid is 0xb6dbbb70, working on task 4
thread 0xb77bcb70 is starting to work
threadid is 0xb77bcb70, working on task 5
thread 0xb63bab70 is starting to work
threadid is 0xb63bab70, working on task 6
thread 0xb6dbbb70 is starting to work
threadid is 0xb6dbbb70, working on task 7
thread 0xb77bcb70 is starting to work
threadid is 0xb77bcb70, working on task 8
thread 0xb63bab70 is starting to work
threadid is 0xb63bab70, working on task 9
thread 0xb6dbbb70 is waiting
thread 0xb77bcb70 is waiting
thread 0xb63bab70 is waiting
thread 0xb6dbbb70 will exit
thread 0xb77bcb70 will exit
thread 0xb63bab70 will exit

[root@localhost code]#