在Linux上执行pthread教程
我开始在linux上进行pthread编程,在第一个程序中我完全搞糊涂了.以下是我正在运行的程序
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
void *print_message_function( void *ptr );
int main(){
pthread_t thread1, thread2;
char *message1 = "Thread 1";
char *message2 = "Thread 2";
int iret1, iret2;
/* Create independent threads each of which will execute function */
iret1 = pthread_create( &thread1, NULL, print_message_function, (void*) message1);
iret2 = pthread_create( &thread2, NULL, print_message_function, (void*) message2);
/* Wait till threads are complete before main continues. Unless we */
/* wait we run the risk of executing an exit which will terminate */
/* the process and all threads before the threads have completed. */
pthread_join( thread1, NULL);
printf("amit");
pthread_join( thread2, NULL);
printf("Thread 1 returns: %d\n",iret1);
printf("Thread 2 returns: %d\n",iret2);
exit(0);
}
void *print_message_function( void *ptr ){
char *message;
message = (char *) ptr;
printf("%s \n", message);
}
我想知道的第一件事是线程执行的顺序不是顺序的?
第二件事是我内心打印(“amit”);看看main在thread1被终止期间真的停止但是在输出中我们可以看到printf语句首先被执行.整个过程的输出是
线程1
线程2
amitThread 1返回:0
线程2返回:0
解决方法:
First one thing i would like to know is order of thread execution is not sequential ?
不正常.大多数现代操作系统上的线程(Linux上的早期线程实现使用协作式多任务处理)并行执行,并且执行printfs的顺序部分是不确定的. pthread\_joins对事物进行了一些排序,因此:
线程1必须在Amit之前,因为主线程在打印Amit1之前等待线程1完成
线程2必须在线程1返回之前:因为第二个pthread\_join. main中的所有printfs都按照它们在main中出现的顺序出现.
我希望能回答你的问题.我不完全确定你在问什么,但随时可以要求澄清任何一点.