線程池——C語言

網上找到一篇對線程池講解很詳細的資料，學習作者文檔及視頻資料並跟著視頻手敲了一下代碼，鏈接如下：
線程池介紹及視頻講解

threadpool.h

#ifndef _THREADPOOL_H
#define _THREADPOOL_H
typedef struct ThreadPool ThreadPool;
//創建線程池並初始化
ThreadPool* threadPoolCreate(int min, int max, int queueCapacity);

//銷毀線程池
int threadPoolDestroy(ThreadPool* pool);

//給線程池添加任務
void threadPoolAdd(ThreadPool* pool, void(*func)(void*), void* arg);

//獲取線程池工作的線程的個數
int threadPoolBusyNum(ThreadPool* pool);

//獲取線程池活著的線程的個數
int threadPoolAliveNum(ThreadPool* pool);

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

threadpool.c

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

const int NUMBER = 2;

//任務結構體
typedef struct Task
{
    
    void (*function)(void* arg);
    void* arg;
}Task;

//線程池結構體
struct ThreadPool
{
    
    //任務隊列
    Task* taskQ;
    int queueCapacity;  //容量
    int queueSize;      //當前任務個數
    int queueFront;     //隊頭 -> 取數據
    int queueRear;      //隊尾 -> 放數據

    pthread_t managerID;    //管理者線程ID
    pthread_t* threadIDs;   //工作的線程ID

    int minNum;             //最小線程數量
    int maxNum;             //最大線程數量
    int busyNum;            //忙的線程的個數
    int liveNum;            //存活的線程的個數
    int exitNum;            //要殺死的線程個數

    pthread_mutex_t mutexPool;  //鎖整個的線程池
    pthread_mutex_t mutexBusy;  //鎖busyNum變量
    pthread_cond_t notFull;     //任務隊列是不是滿了
    pthread_cond_t notEmpty;    //任務隊列是不是空了

    int shutdown;          //是不是要銷毀線程池，銷毀為1，不銷毀為0
};

ThreadPool* threadPoolCreate(int min, int max, int queueCapacity)
{
    
    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));

        pool->minNum = min;
        pool->maxNum = max;
        pool->busyNum = 0;
        pool->liveNum = min;        //和最小個數相等
        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;
        }

        //任務隊列
        pool->taskQ = (Task*)malloc(sizeof(Task) * queueCapacity);
        pool->queueCapacity = queueCapacity;
        pool->queueSize = 0;
        pool->queueFront = 0;
        pool->queueRear = 0;

        pool->shutdown = 0;

        //創建線程
        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);

    //釋放資源
    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;
    }
    //關閉線程池
    pool->shutdown = 1;
    //阻塞回收管理者線程
    pthread_join(pool->managerID, NULL);
    //喚醒阻塞的消費者線程
    for(int i=0; i<pool->liveNum; i++)
    {
    
        pthread_cond_signal(&pool->notEmpty);
    }
    //釋放堆內存
    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;
}

//生產者
void threadPoolAdd(ThreadPool* pool, void(*func)(void*), void* arg)
{
    
    pthread_mutex_lock(&pool->mutexPool);
    while(pool->queueSize == pool->queueCapacity && !pool->shutdown)
    {
    
        //阻塞生產者線程
        pthread_cond_wait(&pool->notFull, &pool->mutexPool);
    }
    if(pool->shutdown)
    {
    
        pthread_mutex_unlock(&pool->mutexPool);
        return;
    }

    //添加任務
    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 liveNum = pool->liveNum;
    pthread_mutex_unlock(&pool->mutexPool);
    return liveNum;
}

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

    while(1)
    {
    
        pthread_mutex_lock(&pool->mutexPool);
        //當前任務是否為空
        //為什麼是while判斷而不是if判斷？
        //因為，如果有多個線程阻塞，一個解鎖後向後執行，其他的必須在循環判斷隊列是否為空，
        //不然隊列已經空了還往下執行
        while(pool->queueSize == 0 && !pool->shutdown)
        {
    
            //阻塞工作的線程
            pthread_cond_wait(&pool->notEmpty, &pool->mutexPool);
            //判斷是不是要銷毀
            if(pool->exitNum>0)
            {
    
                pool->exitNum--;
                if(pool->liveNum > pool->minNum)
                {
    
                    pool->liveNum--;
                    pthread_mutex_unlock(&pool->mutexPool);
                    threadExit(pool);
                }
            }
        }

        //判斷線程池是否被關閉
        //線程池銷毀中也會全部喚醒阻塞的線程，這時候不管任務隊列是否為空都要結束
        //所以必須要加這個if判斷
        if(pool->shutdown)
        {
    
            pthread_mutex_unlock(&pool->mutexPool);
            threadExit(pool);
        }

        //從任務隊列中取出一個任務
        Task task;
        task.function = pool->taskQ[pool->queueFront].function;
        task.arg = pool->taskQ[pool->queueFront].arg;
        //移動頭節點
        pool->queueFront = (pool->queueFront+1) % pool->queueCapacity;
        pool->queueSize--;
        //解鎖
        pthread_cond_signal(&pool->notFull);
        pthread_mutex_unlock(&pool->mutexPool);

        printf("thread start working...\n");
        pthread_mutex_lock(&pool->mutexBusy);
        pool->busyNum++;
        pthread_mutex_unlock(&pool->mutexBusy);

        task.function(task.arg);
        //(*task.function)(task.arg);
        free(task.arg);
        task.arg = NULL;

        printf("thread end working...\n");
        pthread_mutex_lock(&pool->mutexBusy);
        pool->busyNum--;
        pthread_mutex_unlock(&pool->mutexBusy);
    }

    return NULL;
}

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

    //shutdown只有管理者線程才會修改，所以不需要加鎖
    while(!pool->shutdown)
    {
    
        //每隔3s檢測一次
        sleep(3);

        //取出線程池中任務的數量和當前線程的數量
        pthread_mutex_lock(&pool->mutexPool);
        int queueSize = pool->queueSize;
        int liveNum = pool->liveNum;
        pthread_mutex_unlock(&pool->mutexPool);

        //取出忙的線程的數量
        pthread_mutex_lock(&pool->mutexBusy);
        int busyNum = pool->busyNum;
        pthread_mutex_unlock(&pool->mutexBusy);

        //添加線程
        //任務的個數>存活的線程個數 && 存活的線程數<最大線程數
        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);
        }

        //銷毀線程
        //忙的線程*2<存活的線程數 && 存活的線程>最小線程數
        if(busyNum*2<liveNum && liveNum>pool->minNum)
        {
    
            pthread_mutex_lock(&pool->mutexPool);
            pool->exitNum = NUMBER;
            pthread_mutex_unlock(&pool->mutexPool);
            //讓工作的線程自殺
            for(int i=0; i<NUMBER; i++)
            {
    
                pthread_cond_signal(&pool->notEmpty);
            }
        }
    }
}

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("%s called, %ld exiting...\n", __FUNCTION__, tid);
            break;
        }
    }
    pthread_exit(NULL);
}

測試代碼

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

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

int main()
{
    
    //創建出一個線程池
    ThreadPool* pool = threadPoolCreate(3, 10, 100);
    for(int i=0; i<100; i++)
    {
    
        int* num = (int*)malloc(sizeof(int));
        *num = i + 100;
        threadPoolAdd(pool, taskFunc, num);
    }
    sleep(30);
    threadPoolDestroy(pool);
    return 0;
}