while (pool->cur_queue_size == )

{

       pthread_cond_wait (&(pool->queue_ready),&(pool->queue_lock));

}

#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;

int pool_add_worker (void *(*process) (void *arg), void *arg);

void *thread_routine (void *arg);

static CThread_pool *pool = NULL;

void pool_init (int max_thread_num)

{

     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 = ;

     pool->shutdown = ;

     pool->threadid =

         (pthread_t *) malloc (max_thread_num * sizeof (pthread_t));

    int i = ;

    for (i = ; i < max_thread_num; i++)

     {

         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)

{

    /*构造一个新任务*/

     CThread_worker *newworker =

         (CThread_worker *) malloc (sizeof (CThread_worker));

     newworker->process = process;

     newworker->arg = arg;

     newworker->next = NULL;/*别忘置空*/

     pthread_mutex_lock (&(pool->queue_lock));

    /*将任务加入到等待队列中*/

     CThread_worker *member = pool->queue_head;

    if (member != NULL)

     {

        while (member->next != NULL)

             member = member->next;

         member->next = newworker;

     }

    else

     {

         pool->queue_head = newworker;

     }

     assert (pool->queue_head != NULL);

     pool->cur_queue_size++;

     pthread_mutex_unlock (&(pool->queue_lock));

    /*好了，等待队列中有任务了，唤醒一个等待线程；

     注意如果所有线程都在忙碌，这句没有任何作用*/

     pthread_cond_signal (&(pool->queue_ready));

    return ;

}

/*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 ()

{

    if (pool->shutdown)

        return -;/*防止两次调用*/

     pool->shutdown = ;

    /*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 = ; i < pool->max_thread_num; i++)

         pthread_join (pool->threadid[i], NULL);

     free (pool->threadid);

    /*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);

     }

    /*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);

    /*销毁后指针置空是个好习惯*/

     pool=NULL;

    return ;

}

void * thread_routine (void *arg)

{

     printf ("starting thread 0x%x\n", pthread_self ());

    while ()

     {

         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 ==  && !pool->shutdown)

         {

             printf ("thread 0x%x is waiting\n", pthread_self ());

             pthread_cond_wait (&(pool->queue_ready), &(pool->queue_lock));

         }

        /*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\n", pthread_self ());

             pthread_exit (NULL);

         }

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

        /*assert是调试的好帮手*/

         assert (pool->cur_queue_size != );

         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;

         pool->queue_head = worker->next;

         pthread_mutex_unlock (&(pool->queue_lock));

        /*调用回调函数，执行任务*/

         (*(worker->process)) (worker->arg);

         free (worker);

         worker = NULL;

     }

    /*这一句应该是不可达的*/

     pthread_exit (NULL);

}

//下面是测试代码

void * myprocess (void *arg)

{

     printf ("threadid is 0x%x, working on task %d\n", pthread_self (),*(int *) arg);

     sleep ();/*休息一秒，延长任务的执行时间*/

    return NULL;

}

int main (int argc, char **argv)

{

     pool_init ();/*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) * );

    int i;

    for (i = ; i < ; i++)

     {

         workingnum[i] = i;

         pool_add_worker (myprocess, &workingnum[i]);

     }

    /*等待所有任务完成*/

     sleep ();

    /*销毁线程池*/

     pool_destroy ();

     free (workingnum);

    return ;

}