简单线程池

线程池，简单来说就是有一堆已经创建好的线程（最大数目一定），初始时他们都处于空闲状态，当有新的任务进来，从线程池中取出一个空闲的线程处理任务，然后当任务处理完成之后，该线程被重新放回到线程池中，供其他的任务使用，当线程池中的线程都在处理任务时，就没有空闲线程供使用，此时，若有新的任务产生，只能等待线程池中有线程结束任务空闲才能执行。

首先是用条件变量和互斥量封装的一个状态，用于保护线程池的状态

condition.h

#ifndef _CONDITION_H_ #define _CONDITION_H_ #include <pthread.h> //封装一个互斥量和条件变量作为状态 typedef struct condition { pthread_mutex_t pmutex; pthread_cond_t pcond; }condition_t; //对状态的操作函数 int condition_init(condition_t *cond); int condition_lock(condition_t *cond); int condition_unlock(condition_t *cond); int condition_wait(condition_t *cond); int condition_timedwait(condition_t *cond, const struct timespec *abstime); int condition_signal(condition_t* cond); int condition_broadcast(condition_t *cond); int condition_destroy(condition_t *cond); #endif

condition.c

#include “condition.h” //初始化 int condition_init(condition_t *cond) { int status; if((status = pthread_mutex_init(&cond->pmutex, NULL))) return status; if((status = pthread_cond_init(&cond->pcond, NULL))) return status; return 0; } //加锁 int condition_lock(condition_t *cond) { return pthread_mutex_lock(&cond->pmutex); } //解锁 int condition_unlock(condition_t *cond) { return pthread_mutex_unlock(&cond->pmutex); } //等待 int condition_wait(condition_t *cond) { return pthread_cond_wait(&cond->pcond, &cond->pmutex); } //固定时间等待 int condition_timedwait(condition_t *cond, const struct timespec *abstime) { return pthread_cond_timedwait(&cond->pcond, &cond->pmutex, abstime); } //唤醒一个睡眠线程 int condition_signal(condition_t* cond) { return pthread_cond_signal(&cond->pcond); } //唤醒所有睡眠线程 int condition_broadcast(condition_t *cond) { return pthread_cond_broadcast(&cond->pcond); } //释放 int condition_destroy(condition_t *cond) { int status; if((status = pthread_mutex_destroy(&cond->pmutex))) return status; if((status = pthread_cond_destroy(&cond->pcond))) return status; return 0; }

然后是线程池对应的threadpool.h和threadpool.c

#ifndef _THREAD_POOL_H_ #define _THREAD_POOL_H_ //线程池头文件 #include “condition.h” //封装线程池中的对象需要执行的任务对象 typedef struct task { void *(*run)(void *args); //函数指针，需要执行的任务 void *arg; //参数 struct task *next; //任务队列中下一个任务 }task_t; //下面是线程池结构体 typedef struct threadpool { condition_t ready; //状态量 task_t *first; //任务队列中第一个任务 task_t *last; //任务队列中最后一个任务 int counter; //线程池中已有线程数 int idle; //线程池中kongxi线程数 int max_threads; //线程池最大线程数 int quit; //是否退出标志 }threadpool_t; //线程池初始化 void threadpool_init(threadpool_t *pool, int threads); //往线程池中加入任务 void threadpool_add_task(threadpool_t *pool, void *(*run)(void *arg), void *arg); //摧毁线程池 void threadpool_destroy(threadpool_t *pool); #endif #include “threadpool.h” #include <stdlib.h> #include <stdio.h> #include <string.h> #include <errno.h> #include <time.h> //创建的线程执行 void *thread_routine(void *arg) { struct timespec abstime; int timeout; printf(“thread %d is starting\n”, (int)pthread_self()); threadpool_t *pool = (threadpool_t *)arg; while(1) { timeout = 0; //访问线程池之前需要加锁 condition_lock(&pool->ready); //空闲 pool->idle++; //等待队列有任务到来 或者 收到线程池销毁通知 while(pool->first == NULL && !pool->quit) { //否则线程阻塞等待 printf(“thread %d is waiting\n”, (int)pthread_self()); //获取从当前时间，并加上等待时间， 设置进程的超时睡眠时间 clock_gettime(CLOCK_REALTIME, &abstime); abstime.tv_sec += 2; int status; status = condition_timedwait(&pool->ready, &abstime); //该函数会解锁，允许其他线程访问，当被唤醒时，加锁 if(status == ETIMEDOUT) { printf(“thread %d wait timed out\n”, (int)pthread_self()); timeout = 1; break; } } pool->idle–; if(pool->first != NULL) { //取出等待队列最前的任务，移除任务，并执行任务 task_t *t = pool->first; pool->first = t->next; //由于任务执行需要消耗时间，先解锁让其他线程访问线程池 condition_unlock(&pool->ready); //执行任务 t->run(t->arg); //执行完任务释放内存 free(t); //重新加锁 condition_lock(&pool->ready); } //退出线程池 if(pool->quit && pool->first == NULL) { pool->counter–;//当前工作的线程数-1 //若线程池中没有线程，通知等待线程（主线程）全部任务已经完成 if(pool->counter == 0) { condition_signal(&pool->ready); } condition_unlock(&pool->ready); break; } //超时，跳出销毁线程 if(timeout == 1) { pool->counter–;//当前工作的线程数-1 condition_unlock(&pool->ready); break; } condition_unlock(&pool->ready); } printf(“thread %d is exiting\n”, (int)pthread_self()); return NULL; } //线程池初始化 void threadpool_init(threadpool_t *pool, int threads) { condition_init(&pool->ready); pool->first = NULL; pool->last =NULL; pool->counter =0; pool->idle =0; pool->max_threads = threads; pool->quit =0; } //增加一个任务到线程池 void threadpool_add_task(threadpool_t *pool, void *(*run)(void *arg), void *arg) { //产生一个新的任务 task_t *newtask = (task_t *)malloc(sizeof(task_t)); newtask->run = run; newtask->arg = arg; newtask->next=NULL;//新加的任务放在队列尾端 //线程池的状态被多个线程共享，操作前需要加锁 condition_lock(&pool->ready); if(pool->first == NULL)//第一个任务加入 { pool->first = newtask; } else { pool->last->next = newtask; } pool->last = newtask; //队列尾指向新加入的线程 //线程池中有线程空闲，唤醒 if(pool->idle > 0) { condition_signal(&pool->ready); } //当前线程池中线程个数没有达到设定的最大值，创建一个新的线性 else if(pool->counter < pool->max_threads) { pthread_t tid; pthread_create(&tid, NULL, thread_routine, pool); pool->counter++; } //结束，访问 condition_unlock(&pool->ready); } //线程池销毁 void threadpool_destroy(threadpool_t *pool) { //如果已经调用销毁，直接返回 if(pool->quit) { return; } //加锁 condition_lock(&pool->ready); //设置销毁标记为1 pool->quit = 1; //线程池中线程个数大于0 if(pool->counter > 0) { //对于等待的线程，发送信号唤醒 if(pool->idle > 0) { condition_broadcast(&pool->ready); } //正在执行任务的线程，等待他们结束任务 while(pool->counter) { condition_wait(&pool->ready); } } condition_unlock(&pool->ready); condition_destroy(&pool->ready); }

测试代码：

#include “threadpool.h” #include <unistd.h> #include <stdlib.h> #include <stdio.h> void* mytask(void *arg) { printf(“thread %d is working on task %d\n”, (int)pthread_self(), *(int*)arg); sleep(1); free(arg); return NULL; } //测试代码 int main(void) { threadpool_t pool; //初始化线程池，最多三个线程 threadpool_init(&pool, 3); int i; //创建十个任务 for(i=0; i < 10; i++) { int *arg = malloc(sizeof(int)); *arg = i; threadpool_add_task(&pool, mytask, arg); } threadpool_destroy(&pool); return 0; }