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C/C++多线程

2022年07月19日52qq号

一、pthread_once使相关代码只执行一次

这个函数使用初值为PTHREAD_ONCE_INIT的once_control变量保证init_routine()函数在本进程执行序列中仅执行一次。

#include <pthread.h> 
int pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
#include <iostream> 
#include <pthread.h> 
#include <unistd.h> 
 
using namespace std; 
 
pthread_once_t once = PTHREAD_ONCE_INIT; 
 
void once_run(void) { 
    cout<<"once_run in thread "<<(unsigned int )pthread_self()<<endl; 
} 
 
void * child1(void * arg) 
{ 
    pthread_t tid =pthread_self(); 
    cout<<"thread "<<(unsigned int )tid<<" enter"<<endl; 
    pthread_once(&once,once_run); 
    cout<<"thread "<<tid<<" return"<<endl; 
} 
 
 
void * child2(void * arg) 
{ 
    pthread_t tid =pthread_self(); 
    cout<<"thread "<<(unsigned int )tid<<" enter"<<endl; 
    pthread_once(&once,once_run); 
    cout<<"thread "<<tid<<" return"<<endl; 
} 
 
int main(void) 
{ 
    pthread_t tid1,tid2; 
    cout<<"main thread enter"<<endl; 
    pthread_create(&tid1,NULL,child1,NULL); 
    pthread_create(&tid2,NULL,child2,NULL); 
    sleep(10); 
    cout<<"main thread exit"<<endl; 
    return 0; 
 
} 
 
/* 
main thread enter 
thread 4144080640 enter 
once_run in thread 4144080640 
thread 139667890611968 return 
thread 4152473344 enter 
thread 139667899004672 return 
main thread exit 
 
*/

本文参考链接:https://www.cnblogs.com/hellokitty2/p/10799216.html