进程同步--信号实现--APUE

偏执的太偏执、 2022-08-25 09:15 199阅读 0赞

#include <signal.h>
    #include <unistd.h>
    #include <sys/types.h>
    #include <fcntl.h>
    #include "error_exit.h" 
    
    
    static volatile sig_atomic_t sigflag;
    static sigset_t new_mask, old_mask, zero_mask;
    
    
    static void sig_usr(const int signo)
    {
    	sigflag = 1;
    }
    
    
    //进程信号同步前的准备
    void tell_wait()
    {
    	if (signal(SIGUSR1, sig_usr) == SIG_ERR)
    	  error_exit("signal SIGUSR1 error");
    	if (signal(SIGUSR2, sig_usr) == SIG_ERR)
    	  error_exit("signal SIGUSR2 error");
    
    
    	sigemptyset(&zero_mask);
    	sigemptyset(&new_mask);
    	sigaddset(&new_mask, SIGUSR1);
    	sigaddset(&new_mask, SIGUSR2);
    
    
    	//阻塞SIGUSR1和SIGUSR2，保存当前信号阻塞状态
    	if (sigprocmask(SIG_BLOCK, &new_mask, &old_mask) < 0)
    	  error_exit("sigprocmask error");
    }
    
    
    void tell_parent(pid_t pid)
    {
    	kill(pid, SIGUSR2);  //向父进程发送SIGUSR2信号
    }
    
    
    void wait_parent()
    {
    	while (sigflag == 0)
    	  sigsuspend(&zero_mask);  //等待父进程
    	sigflag = 0;
    
    
    	if (sigprocmask(SIG_SETMASK, &old_mask, NULL) < 0)
    	  error_exit("sigprocmask reset error");
    }
    
    
    void tell_child(pid_t pid)
    {
    	kill(pid, SIGUSR1);  //向子进程发送SIGUSR1信号
    }
    
    
    void wait_child()
    {
    	while (sigflag == 0)
    	  sigsuspend(&zero_mask);  //等待子进程
    	sigflag = 0;
    
    
    	if (sigprocmask(SIG_SETMASK, &old_mask, NULL) < 0)
    	  error_exit("sigprocmask reset error");
    }
    
    
    void print_char(char ch, int file_id)
    {
    	if (write(file_id, &ch, sizeof(ch)) != sizeof(ch))
    	  error_exit("write error");
    	/*char	*ptr;
    	int		c;
    
    
    	for (ptr = str; (c = *ptr++) != 0;)
    	{
    		write(file_id, &c, sizeof(c));
    		usleep(0.1);
    	}*/
    }
    
    
    int main(int argc, char *argv[])
    {
    	pid_t pid;
    	int file_id;
    	int count = 0;
    	char tar_ch;
    
    
    	file_id = open("/home/michael/Documents/linux_stydy/unix/1.txt", O_WRONLY|O_CREAT|O_TRUNC);
    	if (file_id == -1)
    	  error_exit("file open error");
    	tar_ch = count + '0';
    	if (write(file_id, &tar_ch, sizeof(tar_ch)) != sizeof(tar_ch))
    	  error_exit("write error 0");
    	
    	tell_wait();
    
    
    	if ((pid = fork()) < 0)
    	  error_exit("fork error");
    	else if (pid == 0)
    	{
    		//print_char("output from child\n", file_id);
    		//tell_parent(getppid());
    		for (count = 1; count < 9; count++)
    		{
    			wait_parent();
    			print_char(count + '0', file_id);
    			printf("child done\n");
    			tell_parent(getppid());
    		}
    	}
    	else
    	{
    		print_char(count + 1 + '0', file_id);
    		printf("parent done\n");
    		tell_child(pid);
    		for (count = 2; count < 9; count++)
    		{
    			wait_child();
    			print_char(count + '0', file_id);
    			printf("parent done\n");
    			tell_child(pid);
    		}
    	}
    
    
    	return 0;
    }