简单的线程池

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1.线程池基本原理
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该图来自：http://blog.csdn.net/turkeyzhou/article/details/8755976
一般来说实现一个线程池主要包括以下几个组成部分：

1）线程管理器：用于创建并管理线程池。

2）工作线程：线程池中实际执行任务的线程。在初始化线程时会预先创建好固定数目的线程在池中，这些初始化的线程一般处于空闲状态，一般不占用CPU，占用较小的内存空间。

3）任务接口：每个任务必须实现的接口，当线程池的任务队列中有可执行任务时，被空闲的工作线程调去执行（线程的闲与忙是通过互斥量实现的，跟前面文章中的设置标志位差不多），把任务抽象出来形成接口，可以做到线程池与具体的任务无关。

4）任务队列：用来存放没有处理的任务，提供一种缓冲机制，实现这种结构有好几种方法，常用的是队列，主要运用先进先出原理，另外一种是链表之类的数据结构，可以动态的为它分配内存空间，应用中比较灵活，下文中就是用到的链表。

下面的不在赘述百度《线程池技术在并发服务器中的应用》写的非常详细！

转自：http://blog.csdn.net/zouxinfox/article/details/3560891

这里记录一下自己弄个的一个简单的线程池；

头文件：

/* * Thread_pool.h * *  Created on: 2016年4月11日 *      Author: wenjun */#ifndef THREAD_POOL_H_#define THREAD_POOL_H_#include <pthread.h>#include <stdio.h>#include <errno.h>#include <time.h>//线程任务typedef struct thread_task{    void *(*run)(void *arg);//线程执行函数    void *arg;//函参    struct thread_task *next;}thr_task;//协同条件typedef struct thread_condition{    pthread_cond_t thr_cond_t;//条件变量    pthread_mutex_t thr_mutex_t;//互斥锁}thr_condition;//线程池typedef struct thread_pool{    thr_condition ready;//线程协调条件    thr_task *first;//任务链表头指针    thr_task *tail;//任务链表尾指针    int idle;//空闲现正数    int counter;//当前线程池线程数    int max_threads;//最大线程数    int quit;//现正需要摧毁标志}thr_pool;//初始化线程条件int condition_init(thr_condition *cond){    int flag = 0;    //初始化互斥量    if((flag = pthread_mutex_init(&cond->thr_mutex_t, NULL)) != 0)    {        printf("pthread_mutex_init failed %d\n",flag);        return -1;    }    //初始化条件变量    if((flag = pthread_cond_init(&cond->thr_cond_t, NULL)) != 0)    {        printf("pthread_condition_init failed %d\n", flag);        return -1;    }    return 0;}//申请互斥锁int condition_lock(thr_condition *cond){    return pthread_mutex_lock(&cond->thr_mutex_t);}//释放互斥锁int condition_unlock(thr_condition *cond){    return pthread_mutex_unlock(&cond->thr_mutex_t);}//申请条件锁int condition_timewait(thr_condition *cond, const struct timespec *tsptr){    int statu = pthread_cond_timedwait(&cond->thr_cond_t, &cond->thr_mutex_t, tsptr);    return statu;}//申请条件锁int condition_wait(thr_condition *cond){    return pthread_cond_wait(&cond->thr_cond_t, &cond->thr_mutex_t);}//发送条件条件锁信号int condition_signal(thr_condition *cond){    return pthread_cond_signal(&cond->thr_cond_t);}//发送条件锁广播int condition_broadcast(thr_condition *cond){    return pthread_cond_broadcast(&cond->thr_cond_t);}//销毁线程条件变量int condition_destroy(thr_condition *cond){    int flag = 0;    //销毁互斥量    if((flag = pthread_mutex_destroy(&cond->thr_mutex_t)) != 0)    {        printf("pthread_mutex_destroy failed %d\n",flag);        return -1;    }    //销毁条件变量    if((flag = pthread_cond_destroy(&cond->thr_cond_t)) != 0)    {        printf("pthread_condition_destroy failed %d\n", flag);        return -1;    }    return 0;}//线程执行函数void *thread_routine(void *arg){    struct timespec abstime;    int timeout;    printf("thread 0x%x is starting\n", (int)pthread_self());    thr_pool *pool = (thr_pool *)arg;    //等待与处理任务    while(1)    {        condition_lock(&pool->ready);        pool->idle++;        //等待任务        while(pool->first && !pool->quit)        {            timeout = 0;            clock_gettime(CLOCK_REALTIME, &abstime);            abstime.tv_sec += 1000;            printf("thread 0x%x is waiting\n", (int)pthread_self());            int status = condition_timewait(&pool->ready, &abstime);            if(status == ETIMEDOUT ||status != 0)            {                printf("thread 0x%x is wait timed out \n", (int)pthread_self());                timeout = 1;                break;            }            printf("thread 0x%x is wait ending \n", (int)pthread_self());        }        //执行任务        if(pool->first != NULL)        {            thr_task *task = pool->first;            pool->first = pool->first->next;            condition_unlock(&pool->ready);            task->run(task->arg);            //销毁执行完的任务            free(task);        }        //判断是是否需要退出该线程（强制退去）        if(pool->quit && pool->first==NULL)        {            pool->counter--;            if(pool->counter == 0)                condition_signal(&pool->ready);            condition_unlock(&pool->ready);            break;        }        //判断是是否需要退出该线程（无任务）        if(timeout && pool->first)        {            pool->counter--;            if(pool->counter == 0)                condition_signal(&pool->ready);            condition_unlock(&pool->ready);            break;        }        pool->idle--;        condition_unlock(&pool->ready);    }    printf("thread 0x%x is ending\n", (int)pthread_self());    return NULL;}//线程池初始化void thread_pool_init(thr_pool *pool, int threads){    condition_init(&pool->ready);    pool->first = NULL;    pool->tail = NULL;    pool->counter = 0;    pool->idle = 0;    pool->max_threads = threads;    pool->quit = 0;}//线程池添加任务函数int thread_pool_add_task(thr_pool *pool, void *(*run(void *arg)), void *arg){    thr_task *tmp = (thr_task *) malloc(sizeof(thr_task));    if(tmp == NULL)    {        printf("malloc thr_task failed %d\n", errno);        exit(1);    }    tmp->arg = arg;    tmp->next = NULL;    tmp->run = run;    condition_lock(&pool->ready);    if(pool->first == NULL)    {        pool->first = tmp;        pool->tail = tmp;    }    else    {        pool->tail->next = tmp;        pool->tail = tmp;    }    //如果有等待线程则发送条件满足信号否则就向线程池中添加线程    if(pool->idle > 0)    {        condition_signal(&pool->ready);    }    else if(pool->counter < pool->max_threads)    {        pthread_t pthr_id;        int err;        err = pthread_create(&pthr_id, NULL, thread_routine, pool);        if(err != 0)        {            printf("pthread_create fialed %d\n", err);            return -1;        }        pool->counter++;    }    condition_unlock(&pool->ready);    return 0;}//线程池销毁函数void thread_pool_destroy(thr_pool *pool){    if(pool->quit)        return;    condition_lock(&pool->ready);    pool->quit = 1;    if(pool->counter > 0)    {        if(pool->idle > 0)            condition_broadcast(&pool->ready);        while(pool->counter > 0)        {            condition_wait(&pool->ready);        }    }    condition_unlock(&pool->ready);}#endif /* THREAD_POOL_H_ */

测试文件：

/* * thread_pool_test.c * *  Created on: 2016年4月11日 *      Author: wenjun */#include "Thread_pool.h"#include <unistd.h>#include <stdio.h>#include <stdlib.h>void* pool_task_test(void *arg){    printf("thread 0x%x is working on task %d\n", (int)pthread_self(), *(int *)arg);    free(arg);    sleep(1);    return NULL;}int main(void){    thr_pool pool;    thread_pool_init(&pool, 4);    int i;    for(i = 0; i<20 ;++i)    {        int *arg = (int *)malloc(sizeof(int));        if(arg ==NULL)        {            printf("malloc thr_task failed %d\n", errno);            exit(1);        }        *arg = i;        thread_pool_add_task(&pool, pool_task_test, arg);    }    sleep(3);    thread_pool_destroy(&pool);    return 0;}

结果：
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