手写线程池byC

[toc]

https://subingwen.cn/linux/threadpool/#5-%E6%BA%90%E6%96%87%E4%BB%B6%E5%AE%9A%E4%B9%89

大丙讲的真好, b站有视频, 用心拍的, 不像某某机构随便发的垃圾音频课.

C语言版本和C++版本都有.

main.c

#include <stdio.h>
#include "threadpool.h"
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>

void taskFunc(void* arg) {
    int num = *(int*)arg;
    printf("thread %ld is working, number = %d\n", pthread_self(), num);
    sleep(1);
}

int main() {
    ThreadPool* pool = threadPoolCreate(3, 10, 20);
    for (int i = 0; i < 100; i++) {
        int* num = (int*)malloc(sizeof(int));
        *num = i;
        threadPoolAdd(pool, taskFunc, num);
    }

    sleep(30);

    threadPoolDestroy(pool);

    return 0;
}

threadpool.h

/*

唯一的管理者id
若干个工作者线程 数组
任务队列 -> 结构体数组
*/

#include "threadpool.h"
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

const int NUMBER = 2; //管理者线程每次添加或删除的线程数量上限

//任务结构体
typedef struct Task {
    void (*function)(void* arg);
    void* arg;
}Task;

//线程池结构体
struct ThreadPool {
    //任务队列
    Task* taskQ;
    int queueCapacity; //容量
    int queueSize; //当前任务个数
    int queueFront; //队头 -> 取数据
    int queueRear;  //队尾 -> 放数据

    pthread_t managerID; // 管理者线程ID
    pthread_t* threadIDs; // 工作线程ID

    int minNum;  //最小线程数
    int maxNum;  //最大线程数
    int busyNum; //忙碌的线程数
    int liveNum; //存活的线程数, 活着不代表正在干活
    int exitNum; //要销毁的线程个数

    pthread_mutex_t mutexPool; // 锁住整个线程池
    pthread_mutex_t mutexBusy; //锁住busyNum变量, mutexbusy
    pthread_mutex_t notFull;  //任务队列是否慢了
    pthread_mutex_t notEmpty; //任务队列是否空了

    int shutdown; //是否销毁线程池, 销毁为1
};
ThreadPool* threadPoolCreate(int min, int max, int queueSize)
{
    ThreadPool* pool = (ThreadPool*)malloc(sizeof(ThreadPool));
    do
    {
        if (pool == NULL)
        {
            printf("malloc threadpool fail...\n");
            break;
        }

        pool->threadIDs = (pthread_t*)malloc(sizeof(pthread_t) * max);
        if (pool->threadIDs == NULL)
        {
            printf("malloc threadIDs fail...\n");
            break;
        }
        memset(pool->threadIDs, 0, sizeof(pthread_t) * max);
        pool->minNum = min;
        pool->maxNum = max;
        pool->busyNum = 0;
        pool->liveNum = min;    // 和最小个数相等
        pool->exitNum = 0;

        if (pthread_mutex_init(&pool->mutexPool, NULL) != 0 ||
            pthread_mutex_init(&pool->mutexBusy, NULL) != 0 ||
            pthread_cond_init(&pool->notEmpty, NULL) != 0 ||
            pthread_cond_init(&pool->notFull, NULL) != 0)
        {
            printf("mutex or condition init fail...\n");
            break;
        }

        // 任务队列
        pool->taskQ = (Task*)malloc(sizeof(Task) * queueSize);
        pool->queueCapacity = queueSize;
        pool->queueSize = 0;
        pool->queueFront = 0;
        pool->queueRear = 0;

        pool->shutdown = 0;

        // 创建线程
        pthread_create(&pool->managerID, NULL, manager, pool);
        for (int i = 0; i < min; ++i)
        {
            pthread_create(&pool->threadIDs[i], NULL, worker, pool);
        }
        return pool;
    } while (0);

    // 释放资源
    if (pool && pool->threadIDs) free(pool->threadIDs);
    if (pool && pool->taskQ) free(pool->taskQ);
    if (pool) free(pool);

    return NULL;
}

int threadPoolDestroy(ThreadPool* pool)
{
    if (pool == NULL)
    {
        return -1;
    }

    // 关闭线程池
    pool->shutdown = 1;
    // 阻塞回收管理者线程
    pthread_join(pool->managerID, NULL);
    // 唤醒阻塞的消费者线程
    for (int i = 0; i < pool->liveNum; ++i)
    {
        pthread_cond_signal(&pool->notEmpty);
    }
    // 释放堆内存
    if (pool->taskQ)
    {
        free(pool->taskQ);
    }
    if (pool->threadIDs)
    {
        free(pool->threadIDs);
    }

    pthread_mutex_destroy(&pool->mutexPool);
    pthread_mutex_destroy(&pool->mutexBusy);
    pthread_cond_destroy(&pool->notEmpty);
    pthread_cond_destroy(&pool->notFull);

    free(pool);
    pool = NULL;

    return 0;
}


void threadPoolAdd(ThreadPool* pool, void(*func)(void*), void* arg)
{
    pthread_mutex_lock(&pool->mutexPool);
    while (pool->queueSize == pool->queueCapacity && !pool->shutdown)
    {
        // 阻塞生产者线程
        pthread_cond_wait(&pool->notFull, &pool->mutexPool);
    }
    if (pool->shutdown)
    {
        pthread_mutex_unlock(&pool->mutexPool);
        return;
    }
    // 添加任务
    pool->taskQ[pool->queueRear].function = func;
    pool->taskQ[pool->queueRear].arg = arg;
    pool->queueRear = (pool->queueRear + 1) % pool->queueCapacity;
    pool->queueSize++;

    pthread_cond_signal(&pool->notEmpty);
    pthread_mutex_unlock(&pool->mutexPool);
}

int threadPoolBusyNum(ThreadPool* pool)
{
    pthread_mutex_lock(&pool->mutexBusy);
    int busyNum = pool->busyNum;
    pthread_mutex_unlock(&pool->mutexBusy);
    return busyNum;
}

int threadPoolAliveNum(ThreadPool* pool)
{
    pthread_mutex_lock(&pool->mutexPool);
    int aliveNum = pool->liveNum;
    pthread_mutex_unlock(&pool->mutexPool);
    return aliveNum;
}

void* worker(void* arg)
{
    ThreadPool* pool = (ThreadPool*)arg;

    while (1)
    {
        pthread_mutex_lock(&pool->mutexPool);
        // 当前任务队列是否为空
        while (pool->queueSize == 0 && !pool->shutdown)
        {
            // 阻塞工作线程
            pthread_cond_wait(&pool->notEmpty, &pool->mutexPool);

            // 判断是不是要销毁线程
            if (pool->exitNum > 0)
            {
                pool->exitNum--;
                if (pool->liveNum > pool->minNum)
                {
                    pool->liveNum--;
                    pthread_mutex_unlock(&pool->mutexPool);
                    threadExit(pool);
                }
            }
        }

        // 判断线程池是否被关闭了
        if (pool->shutdown)
        {
            pthread_mutex_unlock(&pool->mutexPool);
            threadExit(pool);
        }

        // 从任务队列中取出一个任务
        Task task;
        task.function = pool->taskQ[pool->queueFront].function;
        task.arg = pool->taskQ[pool->queueFront].arg;
        // 移动头结点
        pool->queueFront = (pool->queueFront + 1) % pool->queueCapacity;
        pool->queueSize--;
        // 解锁
        pthread_cond_signal(&pool->notFull);
        pthread_mutex_unlock(&pool->mutexPool);

        printf("thread %ld start working...\n", pthread_self());
        pthread_mutex_lock(&pool->mutexBusy);
        pool->busyNum++;
        pthread_mutex_unlock(&pool->mutexBusy);
        task.function(task.arg);
        free(task.arg);
        task.arg = NULL;

        printf("thread %ld end working...\n", pthread_self());
        pthread_mutex_lock(&pool->mutexBusy);
        pool->busyNum--;
        pthread_mutex_unlock(&pool->mutexBusy);
    }
    return NULL;
}

void* manager(void* arg)
{
    ThreadPool* pool = (ThreadPool*)arg;
    while (!pool->shutdown)
    {
        // 每隔3s检测一次
        sleep(3);

        // 取出线程池中任务的数量和当前线程的数量
        pthread_mutex_lock(&pool->mutexPool);
        int queueSize = pool->queueSize;
        int liveNum = pool->liveNum;
        pthread_mutex_unlock(&pool->mutexPool);

        // 取出忙的线程的数量
        pthread_mutex_lock(&pool->mutexBusy);
        int busyNum = pool->busyNum;
        pthread_mutex_unlock(&pool->mutexBusy);

        // 添加线程
        // 任务的个数>存活的线程个数 && 存活的线程数<最大线程数
        if (queueSize > liveNum && liveNum < pool->maxNum)
        {
            pthread_mutex_lock(&pool->mutexPool);
            int counter = 0;
            for (int i = 0; i < pool->maxNum && counter < NUMBER
                && pool->liveNum < pool->maxNum; ++i)
            {
                if (pool->threadIDs[i] == 0)
                {
                    pthread_create(&pool->threadIDs[i], NULL, worker, pool);
                    counter++;
                    pool->liveNum++;
                }
            }
            pthread_mutex_unlock(&pool->mutexPool);
            printf("Add thread number = %d\n", counter);
        }
        // 销毁线程
        // 忙的线程*2 < 存活的线程数 && 存活的线程>最小线程数
        if (busyNum * 2 < liveNum && liveNum > pool->minNum)
        {
            pthread_mutex_lock(&pool->mutexPool);
            pool->exitNum = NUMBER;
            pthread_mutex_unlock(&pool->mutexPool);
            // 让工作的线程自杀
            for (int i = 0; i < NUMBER; ++i)
            {
                pthread_cond_signal(&pool->notEmpty); 
            }
            //printf("Kill thread number = %d\n", counter);
        }
    }
    return NULL;
}

void threadExit(ThreadPool* pool)
{
    pthread_t tid = pthread_self();
    for (int i = 0; i < pool->maxNum; ++i)
    {
        if (pool->threadIDs[i] == tid)
        {
            pool->threadIDs[i] = 0;
            printf("threadExit() called, %ld exiting...\n", tid);
            break;
        }
    }
    pthread_exit(NULL);
}

threadpool.h

#ifndef _THREADPOOL_H
#define _THREADPOOL_H

typedef struct ThreadPool ThreadPool;

//创建线程池, 并初始化
ThreadPool* threadPoolCreate(int min, int max, int queuesize);

//销毁线程池
int threadPoolDestroy(ThreadPool* pool);

//向线程池中添加任务
void threadPoolAdd(ThreadPool* pool, void(*func)(void*), void*arg);

//获取线程池中工作的线程个数
int threadPoolBusyNum(ThreadPool* pool);

//获取线程池中活着的线程个数
int threadPoolAliveNum(ThreadPool* pool);

/////////////////////////////
void* worker(void* arg);
void* manager(void* arg);
void threadExit(ThreadPool* pool);
#endif