这篇博文记录我完成操作系统实验之进程软中断的过程。
实验要求
编制实现进程软中断通信的程序。
使用系统调用fork()创建两个子进程，
再用系统调用signal()让父进程捕捉键盘上发出的3号quit中断信号，
当父进程接收到3号中断后，
父进程用系统调用kill()向两个子进程分别发出整数值为16和17软中断信号，
子进程获得对应软中断信号，然后分别输出下列信息后终止:
1
2
| Child process 1 is killed by parent !!
Child process 2 is killed by parent !!
|
父进程调用wait()函数等待两个子进程终止后，输出以下信息，结束进程：
1
| Parent process is killed!!
|
程序流程图
注：为了便于实验，即使5s内没有输入quit信号，也不产生SIGALRM来kill子进程,而是显示5s内无中断信号继而直接退出。
代码
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| #include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <wait.h>
int wait_flag;
void stop();
int main()
{
int pid1, pid2;
while ((pid1 = fork()) == -1);
if (pid1 > 0)
{
while ((pid2 = fork()) == -1);
if (pid2 > 0)
{
wait_flag = 1;
signal(3, stop);
sleep(5);
if (!wait_flag)
{
kill(pid1, 16);
kill(pid2, 17);
wait(0);
wait(0);
printf("Parent process is killed !!\r\n");
}
else printf("No signal in 5s");
exit(0);
}
else
{
wait_flag = 1;
signal(17, stop);
signal(3,SIG_IGN);
while(wait_flag!=0);
lockf(1,1,0);
printf("Child process 2 is killed by parent !!\r\n");
lockf(1,0,0);
exit(0);
}
}
else
{
wait_flag = 1;
signal(16, stop);
signal(3,SIG_IGN);
while(wait_flag!=0);
lockf(1,1,0);
printf("Child process 1 is killed by parent !!\r\n");
lockf(1,0,0);
exit(0);
}
return 0;
}
void stop()
{
wait_flag = 0;
}
|
运行结果
符合预期！
拓展创新
为了更好地理解进程软中断通信的原理，尝试探索其他中断信号。
将3号quit信号换成2号del信号，且在子进程接受到16或17号中断时，不直接结束，而是调用startalarm设置alarm(3)，在3秒后生成14号闹钟信号来结束子进程，实现了子进程的延时结束，父进程等待子进程结束后退出。
代码
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| #include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <wait.h>
int wait_flag;
void stop();
void startalarm();
int main()
{
int pid1, pid2;
while ((pid1 = fork()) == -1);
if (pid1 > 0)
{
while ((pid2 = fork()) == -1);
if (pid2 > 0)
{
wait_flag = 1;
signal(2, stop);
sleep(15);
if (!wait_flag)
{
kill(pid1, 16);
kill(pid2, 17);
wait(0);
wait(0);
printf("Parent process is killed !!\r\n");
}
else printf("No signal in 15s!");
exit(0);
}
else
{
wait_flag = 1;
signal(17, startalarm);
signal(14, stop);
signal(2,SIG_IGN);
while(wait_flag!=0);
lockf(1,1,0);
printf("Child process 2 is killed by parent !!\r\n");
lockf(1,0,0);
exit(0);
}
}
else
{
wait_flag = 1;
signal(16, startalarm);
signal(14, stop);
signal(2,SIG_IGN);
while(wait_flag!=0);
lockf(1,1,0);
printf("Child process 1 is killed by parent !!\r\n");
lockf(1,0,0);
exit(0);
}
return 0;
}
void stop()
{
wait_flag = 0;
}
void startalarm()
{
alarm(3);
}
|
运行结果
符合预期！
end
