Passing signals between parent and child processes crashing after 2 outputs

[cwright7101]

I am trying to use signals to pass between a parent and child process, but after the first 2 statements are printed (for example in mine it shows CHILD 0: Running, parent is 4224 PARENT 4224: Telling the Child Process 4225 to start) it just gets stuck running forever! I'm not sure where I am going wrong on this...but any pointers to where I run astray would be appreciated!

#include<stdio.h>
#include<signal.h>
#include<unistd.h>
#include<stdlib.h>
#include<errno.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/wait.h>
void p_sig_usr(int signo){
    if(signo == SIGUSR1){
        printf("*** Parent SIGUSR1 handler - Received 'task started' signal from child ***\n");
    }
    if(signo == SIGUSR2){
        printf("*** Parent SIGUSR2 handler - Received 'task completed' signal from child ***\n");
    }
    else
        printf("unexpected signal received");
    return;
}
void c_sig_usr(int signo){
    if(signo == SIGUSR1){
        printf("*** Child SIGUSR1 handler - Received 'task start' signal from parent ***\n");
    }
    if(signo == SIGUSR2){
        printf("*** Child SIGUSR2 handler - Received 'task complete verification' signal from parent ***\n");
    }
    else
        printf("unexpected signal received");
    return;
}

int main(void)
{
    pid_t child_pid, parent_pid;
    parent_pid = getpid();
    struct sigaction p_sig;
    sigemptyset(&p_sig.sa_mask);
    p_sig.sa_flags = 0;
    p_sig.sa_handler = p_sig_usr;
    child_pid = fork();
    if ( child_pid == -1){
        perror("failed to fork a new process");
        return 1;
    }
    if (child_pid == 0){
        struct sigaction c_sig;
        sigset_t c_myset;
        sigemptyset(&c_sig.sa_mask);
        c_sig.sa_flags = 0;
        c_sig.sa_handler = c_sig_usr;
        printf("CHILD %d: Running, parent is %d\n",child_pid, parent_pid);
        sigfillset(&c_myset);
        sigdelset(&c_myset, SIGUSR1);
        sigsuspend(&c_myset);//suspend until get SIGUSR1
        printf("CHILD: Telling parent that I'm starting task.\n");
        sleep(3);
        kill(parent_pid, SIGUSR1);
        printf("CHILD: Performing task\n");
        sigfillset(&c_myset);
        sigdelset(&c_myset, SIGUSR2);
        sigsuspend(&c_myset);//suspend and wait for SIGUSR2
        printf("CHILD: Telling parent that work is done.\n");
        kill(parent_pid, SIGUSR2);
        printf("CHILD %d: Finished\n", child_pid);
    }
    else{
        struct sigaction p_sig;
        sigset_t p_myset;
        sigemptyset(&p_myset);
        sleep(3);//parent now sleeping to let child set up handlers
        printf("PARENT %d: Telling the Child Process %d to start\n", parent_pid, child_pid);
        kill(child_pid, SIGUSR1);
        sigfillset(&p_myset);
        sigdelset(&p_myset, SIGUSR1);
        sigsuspend(&p_myset);//suspend until get SIGUSR1
        sleep(3);
        kill(child_pid,SIGUSR2);
        printf("PARENT: Told child to notify of task completion.\n");
        sigfillset(&p_myset);
        sigdelset(&p_myset, SIGUSR2);//suspend until get SIGUSR2
        printf("PARENT %d: Finished.", parent_pid);
    }
    return 0;
}

Output I was hoping to achieve with this program is as follows:

CHILD 529: Running, parent is 528.

PARENT 528: Telling child 529 to start.

*** Child SIGUSR1 handler - Received 'task start' signal from parent ***

CHILD: Telling parent that I'm starting task.

CHILD: Performing task.

*** Parent SIGUSR1 handler - Received 'task started' signal from child ***

PARENT: Told child to notify of task completion.

*** Child SIGUSR2 handler - Received 'task complete verification' signal from parent ***

CHILD: Telling parent that work is done.

CHILD 529: Finished.

*** Parent SIGUSR2 handler - Received 'task completed' signal from child ***

PARENT 528: Finished.


Thank you in advance for your help!