分叉,信号以及它们如何与C中的全局变量进行交互

Question

我试图了解fork()/ Linux Kernel如何处理全局变量.

给定代码:

#include<signal.h>
#include<unistd.h>
#include<stdio.h>
#include<errno.h>
#include <sys/types.h>

pid_t pid;
int counter = 2;
void handler1(int sig)
{
 counter = counter - 1;
 printf("%d", counter);
 exit(0);
}
int main()
{
    signal(SIGUSR1, handler1); //Install Handler
    printf("%d", counter);     //Print Parent global variable
    pid = fork( );             //Fork(), child pid = 0, parent's pid = positive int.
    if (pid == 0)              //Parent skips this, child goes into infinite loop
    {
      while(1) {}; // simulate doing some work
    }
    kill(pid, SIGUSR1);        //While child is the loop, parents calls to terminate the child. 
                               //Child will stop the infinite loop, and will not proceed any 
                               //Will it call handler1 ???

    wait(NULL);                //Wait for child to be ripped
                               //Will it call handler1 second time ???
    counter = counter + 1;     //This will surely increment global variable
    printf("%d", counter);
    exit(0);
}

输出是2123 在fork()和信号处理程序被调用之后Unix/Linux内核如何处理全局变量？他们是否在孩子和父母之间分享？

我对这段代码的另一个问题是kill()和wait()将如何处理全局变量以及它们将使用什么样的集合 - 父母或孩子？他们会叫信号处理程序???

谢谢 !

Answer 1

孩子获得全局变量的独立副本.这两份副本 不共享.