Linux C下实现线程池
下面是原文链接，我是照着敲的。。。hi.baidu.com/boahegcrmdghots/item/f3ca1a3c2d47fcc52e8ec2e1
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<pthread.h>
#include<assert.h>
/*
线程池里所有运行和等待的任务都是一个thread_job
由于所有任务都在链表中，所以是一个链表结构
*/
typedef struct job
{
/*回调函数，任务运行时会调用次函数，注意也可以声明为其他形式*/
void * (*process)(void *arg);
void *arg;
struct job *next;
}thread_job;
/*线程池结构*/
typedef struct
{
pthread_mutex_t queue_lock;
pthread_cond_t queue_ready;
/*链表结构，线程池中所有等待任务*/
thread_job *queue_head;
/*线程池销毁标记*/
int destroy;
/**/
pthread_t *threadid;
/*线程池中允许的最大线程数目*/
int max_thread_num;
/*等待队列的任务数目*/
int cur_queue_size;
}thread_pool;
int add_job(void *(*process)(void *arg), void *arg);
void *thread_runtine(void *arg);
/*把线程池指针设为静态*/
static thread_pool *pool = NULL;
/*初始化线程池*/
void pool_init(int max_thread_num)
{
pool = (thread_pool *)malloc(sizeof(thread_pool));
pthread_mutex_init(&(pool->queue_lock), NULL);
pthread_cond_init(&(pool->queue_ready), NULL);
pool->queue_head = NULL;
pool->max_thread_num = max_thread_num;
pool->cur_queue_size = 0;
/*为线程池中的各个线程分配空间 做初始化*/
pool->threadid = (pthread_t *)malloc(max_thread_num*sizeof(pthread_t));
int i = 0;
/*创建max_thread_num个线程*/
for(i=0; i<max_thread_num; i++)
{
/*理解线程创建函数各个参数, 每个线程都会执行thread_runtine函数*/
pthread_create(&(pool->threadid[i]), NULL, thread_runtine, NULL);
}
}
/*每个线程都会执行runtine函数, 每个thread_rutine函数都是取出一个thread_job处理任务
也就是说，线程池中可能有很多个thread_job需要cur_queue_size个线程去处理,处理前要
先对线程池加锁，保证当前处理任务的线程处理thread_job时不会收到其他线程影响,能够互斥访问*/
void *thread_runtine(void *arg)
{
printf("starting thread 0x%x\n", (unsigned int)pthread_self());
while(1)
{
/*对线程池加互斥锁*/
pthread_mutex_lock(&(pool->queue_lock));
/*如果线程当前的等待队列为0,并且没有被销毁，则处于阻塞状态
pthread_cond_wait是一个原子操作，等待前解锁，唤醒后会加锁*/
while( (pool->cur_queue_size == 0) && (!pool->destroy) )
{
printf("thread 0x%x is waiting\n", (unsigned int)pthread_self());
pthread_cond_wait(&(pool->queue_ready), &(pool->queue_lock));
}
/*线程池销毁了*/
if(pool->destroy)
{
pthread_mutex_lock(&(pool->queue_lock));
printf("thread 0x%x will exit\n", (unsigned int)pthread_self());
pthread_exit(NULL);
}
printf("thread 0x%x is starting to work\n", (unsigned int)pthread_self());
assert(pool->cur_queue_size != 0);
assert(pool->queue_head != NULL);
/*等待队列长度减1,并取出线程池中的线程链表中的头元素*/
pool->cur_queue_size--;
thread_job *job = pool->queue_head;
pool->queue_head = job->next;
pthread_mutex_unlock(&(pool->queue_lock));
/*调用回调函数，执行任务, */
(*(job->process))(job->arg);
free(job);
job = NULL;
}
/*这一句是不可达的*/
pthread_exit(NULL);
}
/*向线程池中添加任务, 重点理解参数, 每个任务要做的事体现在process回调函数上*/
int pool_add_job(void *(*process)(void *arg), void *arg)
{
thread_job *newjob = (thread_job *)malloc(sizeof(thread_job));
newjob->process = process;
newjob->arg = arg;
newjob->next = NULL;
/*对线程池加锁*/
pthread_mutex_lock(&(pool->queue_lock));
thread_job *member = pool->queue_head;
if(member != NULL)
{
while(member->next != NULL)
member = member->next;
member->next = newjob;
}
else
{
pool->queue_head = newjob;
}
assert(pool->queue_head != NULL);
pool->cur_queue_size++;
pthread_mutex_unlock(&(pool->queue_lock));
/*等待队列中有任务了，唤醒一个等待线程，如果所有线程都在忙碌，这句没有任何作用*/
pthread_cond_signal(&(pool->queue_ready));
return 0;
}
int pool_destroy()
{
if(pool->destroy)
return -1;
pool->destroy = 1;
/*唤醒所有等待线程，线程池要销毁了*/
pthread_cond_broadcast(&(pool->queue_ready));
/*阻塞等待线程退出，否则变成僵尸了*/
int i = 0;
for(i=0; i<pool->max_thread_num; i++)
{
pthread_join(pool->threadid[i], NULL);
}
free(pool->threadid);
thread_job *head = NULL;
while(pool->queue_head != NULL)
{
head = pool->queue_head;
pool->queue_head = pool->queue_head->next;
free(head);
}
/*条件变量和互斥量也要销毁*/
pthread_mutex_destroy(&(pool->queue_lock));
pthread_cond_destroy(&(pool->queue_ready));
free(pool);
pool = NULL;
return 0;
}
void* myprocess(void *arg)
{
printf("threadid is 0x%x, working on task %d\n", (unsigned int)pthread_self(), *(int *)arg);
sleep(1);
return NULL;
}
int main(int argc, char **argv)
{
pool_init(3);/*初始话含有3个线程的线程池*/
int *workingnum = (int *)malloc(sizeof(int)*10);
int i = 0;
for(i=0; i<10; i++)
{
workingnum[i] = i;
pool_add_job(myprocess, &workingnum[i]);
}
sleep(5);
pool_destroy();
free(workingnum);
return 0;
}