threadpool.c

#include "threadpool.h"
#include "log.h"
  
//做一些初始化操作
threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size)
{
	int i;
	threadpool_t *pool = NULL;
	do {
		if((pool = (threadpool_t *)malloc(sizeof(threadpool_t))) == NULL) {  
			LogWrite(ERROR, "%d %s:%s", __LINE__, "malloc threadpool failed", strerror(errno));
			break;
		}
 
		pool->min_thr_num = min_thr_num;		//线程池最小线程数
		pool->max_thr_num = max_thr_num;		//线程池最大线程数
		pool->busy_thr_num = 0;           		//忙状态的线程数初始值为0
		pool->live_thr_num = min_thr_num; 		//活着的线程数 初值=最小线程数 
		pool->wait_exit_thr_num = 0;      		//要销毁的线程个数初始值也初始为0.
 
 
		pool->queue_size = 0;					//任务队列实际元素个数初始值为0
		pool->queue_max_size = queue_max_size;	//任务队列最大元素个数。
		pool->queue_front = 0;
		pool->queue_rear = 0;
		pool->shutdown = false;					//不关闭线程池
 
		/* 根据最大线程上限数， 给工作线程数组开辟空间, 并清零 */
		pool->threads = (pthread_t *)malloc(sizeof(pthread_t)*max_thr_num); //线程池中线程最大个数
		if (pool->threads == NULL) {
			LogWrite(ERROR, "%d %s:%s", __LINE__, "malloc threads failed", strerror(errno));
			break;
		}
		memset(pool->threads, 0, sizeof(pthread_t)*max_thr_num);
 
		/* 队列开辟空间 */
		pool->task_queue = (threadpool_task_t *)malloc(sizeof(threadpool_task_t)*queue_max_size); //每个元素都是一个结构体，结构体中有一个函数指针和一个void*的指针。
		if (pool->task_queue == NULL) {
			LogWrite(ERROR, "%d %s:%s", __LINE__, "malloc task_queue failed", strerror(errno));
			break;
		}
 
		/* 初始化互斥琐、条件变量 */
		if (pthread_mutex_init(&(pool->lock), NULL) != 0 || pthread_mutex_init(&(pool->thread_counter), NULL) != 0 || 
			pthread_cond_init(&(pool->queue_not_empty), NULL) != 0 || pthread_cond_init(&(pool->queue_not_full), NULL) != 0)
		{
			LogWrite(ERROR, "%d %s:%s", __LINE__, "init the lock or cond failed", strerror(errno));
			break;
		}
 
		for (i = 0; i < min_thr_num; i++) {
			pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);
			LogWrite(DEBUG, "%d %s%x", __LINE__, "start thread 0x", (unsigned int)pool->threads[i]);
		}
		pthread_create(&(pool->adjust_tid), NULL, adjust_thread, (void *)pool); /* 启动管理者线程 */
		pthread_detach(pool->adjust_tid);  //把管理线程设置为分离的，系统帮助回收资源。
		LogWrite(DEBUG, "%d %s", __LINE__, "adjust_thread start");
 
		//等待线程创建完成再回到主函数中。
		for (i = 0; i < min_thr_num; i++) {
			pthread_join(pool->threads[i], NULL);
		}
		//sleep(1);  //等待线程创建完成再回到主函数中。
		return pool;
 
	} while (0);
 
	threadpool_free(pool);      /* 前面代码调用失败时，释放poll存储空间 */
 
	return NULL;
}

/* 线程池中各个工作线程 */
void *threadpool_thread(void *threadpool)
{
	threadpool_t *pool = (threadpool_t*)threadpool;
 
	threadpool_task_t task;
 
	while(true)
	{
		/*刚创建出线程，等待任务队列里 有任务，否则阻塞等待任务队列里有任务后再唤醒接收任务*/
		pthread_mutex_lock( &(pool->lock) );
 
		/*queue_size == 0 说明没有任务，调 wait 阻塞在条件变量上, 若有任务，跳过该while*/
		while( (pool->queue_size ==0) && (!pool->shutdown) ) //线程池没有任务且不关闭线程池。
		{
			LogWrite(DEBUG, "%d %s%x %s", __LINE__, "thread 0x", (unsigned int)pthread_self(), "is waitting");
			pthread_cond_wait(&(pool->queue_not_empty), &(pool->lock));//线程阻塞在这个条件变量上
 
			/*清除指定数目的空闲线程，如果要结束的线程个数大于0，结束线程*/
			if( pool->wait_exit_thr_num > 0)  /* 要销毁的线程个数大于0 */
			{
				pool->wait_exit_thr_num--;
 
				/*如果线程池里线程个数大于最小值时可以结束当前线程*/
				if (pool->live_thr_num > pool->min_thr_num) {
					LogWrite(DEBUG, "%d %s%x %s", __LINE__, "thread 0x", (unsigned int)pthread_self(), "is exiting");
					pool->live_thr_num--;
					pthread_mutex_unlock(&(pool->lock));
					pthread_exit(NULL);
				}
			}
		}
 
		/*如果指定了true，要关闭线程池里的每个线程，自行退出处理*/
		if(pool->shutdown)
		{
			pthread_mutex_unlock ( &(pool->lock) );
			LogWrite(DEBUG, "%d %s%x %s", __LINE__, "thread 0x", (unsigned int)pthread_self(), "is exiting");
			pthread_exit(NULL);     /* 线程自行结束 */
		}
 
		//从任务队列里获取任务，是一个出队操作
		task.function=pool->task_queue[pool->queue_front ].function;
		task.arg = pool->task_queue[pool->queue_front ].arg;
 
		pool->queue_front = ((pool->queue_front +1) % pool->queue_max_size);//队头指针向后移动一位。
		pool->queue_size--;
 
		/*任务队列中出了一个元素，还有位置 ，唤醒阻塞在这个条件变量上的线程，现在通知可以有新的任务添加进来*/
		pthread_cond_broadcast(&(pool->queue_not_full)); //queue_not_full另一个条件变量。
 
		/*任务取出后，立即将 线程池琐 释放*/
		pthread_mutex_unlock(&(pool->lock));
 
		/*执行任务*/ 
		LogWrite(DEBUG, "%d %s%x %s", __LINE__, "thread 0x", (unsigned int)pthread_self(), "start working");
		pthread_mutex_lock(&(pool->thread_counter));         /*忙状态线程数变量琐*/
		pool->busy_thr_num++;                                /*忙状态线程数+1*/
		pthread_mutex_unlock(&(pool->thread_counter));
		(task.function)(task.arg);  /*执行回调函数任务，相当于process(arg)  */

		/*任务结束处理*/ 
		LogWrite(DEBUG, "%d %s%x %s", __LINE__, "thread 0x", (unsigned int)pthread_self(), "end working");
		usleep(10000); 
 
		pthread_mutex_lock(&(pool->thread_counter));
		pool->busy_thr_num--;                 /*处理掉一个任务，忙状态数线程数-1*/
		pthread_mutex_unlock(&(pool->thread_counter));
 
	}
	pthread_exit(NULL);
}

int is_thread_alive(pthread_t tid)
{
	int kill_rc = pthread_kill(tid, 0);     //发0号信号，测试线程是否存活
	if (kill_rc == ESRCH) {
		return false;
	}
 
	return true;
}

/* 管理线程 */
void *adjust_thread(void *threadpool)
{
	int i;
	threadpool_t *pool = (threadpool_t *)threadpool ;
 
	while( !(pool->shutdown)  ) //线程池没有关闭
	{
		sleep(DEFAULT_TIME);                                    /*定时 对线程池管理*/
		LogWrite(DEBUG, "%d %s", __LINE__, "10s is finish,start test thread pool");

		pthread_mutex_lock(&(pool->lock));
		int queue_size = pool->queue_size;                      /* 关注 任务数 */
		int live_thr_num = pool->live_thr_num;                  /* 存活 线程数 */
		pthread_mutex_unlock(&(pool->lock));
 
		pthread_mutex_lock(&(pool->thread_counter));
		int busy_thr_num = pool->busy_thr_num; 
		pthread_mutex_unlock(&(pool->thread_counter));                 /* 忙着的线程数 */
		LogWrite(DEBUG, "%d %s %d", __LINE__, "busy thread number is", busy_thr_num);
			
		/* 创建新线程 算法： 任务数大于最小线程池个数, 且存活的线程数少于最大线程个数时 如：30>=10 && 40<100*/
		if (queue_size >= MIN_WAIT_TASK_NUM && live_thr_num < pool->max_thr_num)
		{
			LogWrite(DEBUG, "%d %s", __LINE__, "create new thread");
 
			pthread_mutex_lock(&(pool->lock));  
			int add = 0;
 
			/*一次增加 DEFAULT_THREAD 个线程*/
			for (i = 0; i < pool->max_thr_num && add < DEFAULT_THREAD_VARY
					&& pool->live_thr_num < pool->max_thr_num; i++)
			{
				if (pool->threads[i] == 0 || !is_thread_alive(pool->threads[i]))
				{
					pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);
					add++;
					pool->live_thr_num++;
				}
			}
			pthread_mutex_unlock(&(pool->lock));
 
		}
 
		/* 销毁多余的空闲线程 算法：忙线程X2 小于 存活的线程数 且 存活的线程数 大于 最小线程数时*/
		if ((busy_thr_num * 2) < live_thr_num  &&  live_thr_num > pool->min_thr_num)
		{
			LogWrite(DEBUG, "%d %s", __LINE__, "delete pthread");
 
			/* 一次销毁DEFAULT_THREAD个线程, 隨機10個即可 */
			pthread_mutex_lock(&(pool->lock));
			pool->wait_exit_thr_num = DEFAULT_THREAD_VARY;     
			pthread_mutex_unlock(&(pool->lock));
 
			for (i = 0; i < DEFAULT_THREAD_VARY; i++) 
			{
				/* 通知处在空闲状态的线程, 他们会自行终止*/
				pthread_cond_signal(&(pool->queue_not_empty));
			}
		}
	}
	return NULL;
}

/* 向任务队列中， 添加一个任务 */
int threadpool_add(threadpool_t *pool, void *(*function)(void *arg), void *arg)
{
	pthread_mutex_lock( &(pool->lock) );
 
	/* ==为真，队列已经满， 调wait阻塞 */
	while ((pool->queue_size == pool->queue_max_size) && (!pool->shutdown))
	{
		pthread_cond_wait(&(pool->queue_not_full), &(pool->lock));
	}
 
	if (pool->shutdown)
	{			    
		pthread_mutex_unlock(&(pool->lock));	
	}

	/* 清空 工作线程 调用的回调函数 的参数arg */
	if (pool->task_queue[pool->queue_rear].arg != NULL)
	{
	 	free(pool->task_queue[pool->queue_rear].arg);//这里调用free不安全，因为有可能线程执行函数中, 忙符合时低概率
	 	pool->task_queue[pool->queue_rear].arg = NULL;
	}
 
	/*添加任务到任务队列里*/
	pool->task_queue[pool->queue_rear].function = function; //在队列的尾部添加元素
	pool->task_queue[pool->queue_rear].arg = arg;
	pool->queue_rear = (pool->queue_rear + 1) % pool->queue_max_size; /* 队尾指针移动, 模拟环形 */
	pool->queue_size++;
 
	/*添加完任务后，队列不为空，唤醒阻塞在为空的那个条件变量上中的线程*/
	pthread_cond_signal(&(pool->queue_not_empty));
	pthread_mutex_unlock(&(pool->lock));
 
	return EXIT_SUCCESS_CODE;
}

int threadpool_free(threadpool_t *pool)
{
	if (pool == NULL) {
		return EXIT_FAIL_CODE;
	}
 
	if (pool->task_queue) {   //释放任务队列
		free(pool->task_queue);
	}
	if (pool->threads) {   //释放线程池数组以及各种锁。
		free(pool->threads);
		pthread_mutex_unlock(&(pool->lock));
		pthread_mutex_destroy(&(pool->lock));
		pthread_mutex_unlock(&(pool->thread_counter));
		pthread_mutex_destroy(&(pool->thread_counter));
		pthread_cond_destroy(&(pool->queue_not_empty));
		pthread_cond_destroy(&(pool->queue_not_full));
	}
	free(pool);
	pool = NULL;
 
	return EXIT_SUCCESS_CODE;
}

int threadpool_destroy(threadpool_t *pool)
{
	int i;
	if (pool == NULL) {
		return EXIT_FAIL_CODE;
	}
	pool->shutdown = true;
 
 	/*通知所有的空闲线程, 不需要循环广播*/
	pthread_cond_broadcast(&(pool->queue_not_empty));
	for (i = 0; i < pool->live_thr_num; i++) {
		pthread_join(pool->threads[i], NULL);
	}
	threadpool_free(pool);
 
	return EXIT_SUCCESS_CODE;
}

/* 线程池中的线程，模拟处理业务 */
void *process(void *arg)
{
	LogWrite(DEBUG, "%d %s%x %s %d", __LINE__, "thread 0x", (unsigned int)pthread_self(), "working on task", *(int *)arg);
	sleep(5);
	LogWrite(ERROR, "%d %s %d %s", __LINE__, "task", *(int *)arg, "is end");
	return NULL;
}

/*
int main()
{
	threadpool_t *thp = threadpool_create(3,30,30);//创建线程池，池里最小3个线程，最大100，队列最大100
	if (thp == NULL) {
		LogWrite(ERROR, "%d %s", __LINE__, "thread pool create error");
		return EXIT_FAIL_CODE;
	}
	LogWrite(INFO, "%d %s", __LINE__, "thread pool inited");
 
	int num[30], i;
	for (i = 0; i < 30; i++) {
		num[i] = i;
		LogWrite(INFO, "%d %s %d", __LINE__, "add task", i);
		threadpool_add(thp, process, (void*)&num[i]);     //向任务队列中添加任务
	}

	while(true) {
		pthread_mutex_lock(&(thp->thread_counter));
		int busyNum = thp->busy_thr_num;
		int taskNum = thp->queue_size;
		pthread_mutex_unlock(&(thp->thread_counter));

		// 释放线程池
		if (busyNum == 0 && taskNum == 0) {	
				LogWrite(DEBUG, "%d %s", __LINE__, "busyNum == 0 && taskNum == 0, clean up thread pool");
				threadpool_destroy(thp);
				return EXIT_SUCCESS_CODE;
		}
	}	
	printf("never go here\n");
}
*/
/* gcc threadpool.c -o threadpool -lpthread */