请问各位linux里pthread_join(*(pthread_t*)arg, NULL);这句话代表什么意思？
void* thread1(void* arg){
printf("enter thread1\n");
printf("this is thread1, g_Flag: %d, thread id is %u\n",g_Flag, (unsigned int)pthread_self());
pthread_mutex_lock(&mutex);
if(g_Flag == 2)
pthread_cond_signal(&cond);
g_Flag = 1;
printf("this is thread1, g_Flag: %d, thread id is %u\n",g_Flag, (unsigned int)pthread_self());
pthread_mutex_unlock(&mutex);
pthread_join(*(pthread_t*)arg, NULL);
printf("leave thread1\n");
pthread_exit(0);
}
如题，有这么一个线程，可不知道pthread_join(*(pthread_t*)arg, NULL);这句话代表什么意思，哪位大虾可以告知一下，不胜感激！ 函数pthread_join用来等待一个线程的结束 回复【1楼】ljt80158015
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这个我知道，可里面*(pthread_t*)arg这个参数我不知道代表什么意思？ 回复【2楼】w282529350馒头
回复【1楼】ljt80158015
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这个我知道，可里面*(pthread_t*)arg这个参数我不知道代表什么意思？
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arg 是线程thread1传递进来的 回复【3楼】ljt80158015
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谢谢您的回答，我把完整的程序贴出来，您帮我看下吧，您说“arg 是线程thread1传递进来的”，那这个参数代表什么意思？是不是等待线程2结束的意思？
1）有一int型全局变量g_Flag初始值为0；
2）在主线称中起动线程1，打印“this is thread1”，并将g_Flag设置为1
3）在主线称中启动线程2，打印“this is thread2”，并将g_Flag设置为2
4）线程序1需要在线程2退出后才能退出
5）主线程在检测到g_Flag从1变为2，或者从2变为1的时候退出
*/
#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#include<errno.h>
#include<unistd.h>
typedef void* (*fun)(void*);
int g_Flag=0;
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
void* thread1(void*);
void* thread2(void*);
/*
*when program is started, a single thread is created, called the initial thread or main thread.
*Additional threads are created by pthread_create.
*So we just need to create two thread in main().
*/
int main(int argc, char** argv)
{
printf("enter main\n");
pthread_t tid1, tid2;
int rc1=0, rc2=0;
rc2 = pthread_create(&tid2, NULL, thread2, NULL);
if(rc2 != 0)
printf("%s: %d\n",__func__, strerror(rc2));
rc1 = pthread_create(&tid1, NULL, thread1, &tid2);
if(rc1 != 0)
printf("%s: %d\n",__func__, strerror(rc1));
pthread_cond_wait(&cond, &mutex);
printf("leave main\n");
exit(0);
}
/*
* thread1() will be execute by thread1, after pthread_create()
* it will set g_Flag = 1;
*/
void* thread1(void* arg)
{
printf("enter thread1\n");
printf("this is thread1, g_Flag: %d, thread id is %u\n",g_Flag, (unsigned int)pthread_self());
pthread_mutex_lock(&mutex);
if(g_Flag == 2)
pthread_cond_signal(&cond);
g_Flag = 1;
printf("this is thread1, g_Flag: %d, thread id is %u\n",g_Flag, (unsigned int)pthread_self());
pthread_mutex_unlock(&mutex);
pthread_join(*(pthread_t*)arg, NULL);
printf("leave thread1\n");
pthread_exit(0);
}
/*
* thread2() will be execute by thread2, after pthread_create()
* it will set g_Flag = 2;
*/
void* thread2(void* arg)
{
printf("enter thread2\n");
printf("this is thread2, g_Flag: %d, thread id is %u\n",g_Flag, (unsigned int)pthread_self());
pthread_mutex_lock(&mutex);
if(g_Flag == 1)
pthread_cond_signal(&cond);
g_Flag = 2;
printf("this is thread2, g_Flag: %d, thread id is %u\n",g_Flag, (unsigned int)pthread_self());
pthread_mutex_unlock(&mutex);
printf("leave thread2\n");
pthread_exit(0);
}
编译运行可以得到符合要求的结果！
enter main
enter thread2
this is thread2, g_Flag: 0, thread id is 3086408592
this is thread2, g_Flag: 2, thread id is 3086408592
leave thread2
enter thread1
this is thread1, g_Flag: 2, thread id is 3075918736
this is thread1, g_Flag: 1, thread id is 3075918736
leave thread1
leave main 回复【3楼】ljt80158015
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再次感谢！我懂了。rc1 = pthread_create(&tid1, NULL, thread1, &tid2); 这里传递参数的，怪我看代码太不仔细了..... pthread_join用来等待线程结束并释放线程占用的资源。 回复【6楼】kelp
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谢谢 一般都是第一个参数写进程的ID，这个程序里写的传递来的参数，以为是新用法....
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