c - 如何使进程在等待带有 pause() 的信号但未收到信号时继续执行

Question

我是论坛的新手，我一直在谷歌上搜索我的问题，但没有找到。无论如何，我不是很擅长在论坛中搜索，所以如果这个问题已经得到解答，请原谅。好的，让我们进入正题:我正在为大学做一个小项目，其中我有以下用 C 编写的代码:

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>

int ARB,A,B,X,Y,Z,i;

void senyal(){ //signal USR1 method
  if(getpid()==A){
    printf("I'm A process, I've received the signal\n");
    system("pstree");
   }

  else if(getpid()==B){
    printf("I'm B process, I've received the signal\n");
    system("pstree");
  }
  else if(getpid()==X){
    printf("I'm X process, I've received the signal\n");
    execlp("ls", "ls", "-al", "*.c", NULL);
  }
  else if(getpid()==Y){
    printf("I'm Y process, I've received the signal\n");
    execlp("ls", "ls", "-al", "*.c", NULL);
  }
}

int main (int argc, char *argv[]){
 char p=argv[1][0];
 int num=(int)p;

  pid_t pid;
  pid_t pid2;
  pid_t pid3;
  ARB=getpid();
  pid=fork(); //Creates father ARB and A child
    if(pid==-1){
        printf ("Error");
        }
    else if(pid==0){ // A child
        printf ("I'm A process: my pid is %d. My father is %d \n",getpid(), ARB);
        A=getpid();
     if(num==65||num==97){
       num=A;}
    pid2=fork(); //A is the father and creates B child
          if(pid2==-1){
      printf ("Error2");}
          else if(pid2==0){// B child 
        B=getpid();
         if(num==66||num==98){
           num=B;}
        printf("I'm B process , my pid is %d. My father is %d. My grandfather is %d \n",getpid(),getppid(),ARB);
        pid3=fork();//Creates X
          switch(pid3){
        case -1: printf("Error3");
             break;
        case 0:  printf("I'm  X process, my pid is %d. My father is %d. My grandfather is %d. My great grandfather is %d\n",getpid(),getppid(),A,ARB);
             X=getpid();
              if(num==88||num==120){
                num=X;}
             signal(10,senyal);
             printf("I'm X (%d) and I die\n",X);
             exit(X);
             break;
        default: 
             break;
          }
       pid3=fork();//Creates Y  
          switch(pid3){
        case -1: printf("Error no he podido crear el proceso hijo\n");
             break;
        case 0:  printf(I'm  Y process, my pid is %d. My father is %d. My grandfather is %d. My great grandfather is %d\n",getpid(),getppid(),A,ARB);
                 Y=getpid();
              if(num==89||num==121){
                num=Y;}
             signal(10,senyal);
             printf("I'm Y (%d) and I die\n",Y);
             exit(Y);
             break;
        default: 
              break;
          }
          pid3=fork();//Creates Z
           switch(pid3){
        case -1: printf("Couldn't create children proccess\n");
              break;
        case 0:  printf("I'm  Z process, my pid is %d. My father is %d. My grandfather is %d. My great grandfather is %d\n",getpid(),getppid(),A,ARB);
             Z=getpid();
             printf("I'm Z (%d) and I die\n",Z);
             sleep(argc); //

             kill(num,SIGUSR1);//sends a signal to any of the other process (A/B/X/Y)
             exit(Z);

             break;
        default: 
             break;
          }
        wait();//wait for the childrens' death
        wait();
        wait();
        printf("I'm B(%d) and I die\n",B);
        exit(B);//B's death
      }

          else{//Father A
        signal(10,senyal);
        wait();//await B's death
        printf("I'm A (%d) and I die\n",A);
        exit(A); //A's death

      }

    }    
    else{//Padre ARB
       printf ("\nI'm the process arb: my pid is %d\n",getpid());   
       signal(10,senyal);
       wait();  //await A's death     
       }
wait();     




                printf("I'm arb (%d) and I die\n",ARB);
exit (0);//ARB's death

}

所以基本上代码应该做的是创建一个进程树，然后接收一个参数，该参数指示需要接收进程 Z 发送的 USGR1 类型信号的进程的 PID。我的问题是我希望每个进程都准备好接收信号，但如果进程没有收到信号(例如进程 A 正在等待并准备好接收来自 Z 的信号但 Z 将其发送给 B ) 我不知道如何告诉该过程继续进行，而不是永远陷入停顿状态。基本上就是这样，对不起，如果我犯了任何语法或解释错误，但顺便说一句，我来自西类牙。感谢任何愿意回答的人!

Answer 1

来自 pause() 的手册页:

DESCRIPTION

pause() causes the calling process (or thread) to sleep until a signal is delivered that either terminates the process or causes the invocation of a signal-catching function.

所以你需要另一个 thread 延迟 sleep() 或类似的东西，并在一段时间后发送信号。或者使用暂停以外的其他方式，例如 sleep 。