How to implement producer-consumer using processes?

Question

I'm trying to implement a producer-consumer application using 1 parent process and 1 child process. The program should work like this:

1 - The parent process is the producer and the child process is the consumer.
2 - The producer creates a file, the consumer removes the file.
3 - After the file has been created, the parent process sends a SIGUSR1 signal to the child process which then removes the file and sends a SIGUSR2 signal to the parent, signaling it that the file can be created again.

I've tried implementing this problem but I keep getting this error:

User defined signal 1: 30.   

I don't really understand what could be the problem. I've just started learning about process and signals and maybe I'm missing something. Any help would be appreciated. Here's my implementation:

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

pid_t child, parent;

void producer()
{
    system("touch file");
    printf("File was created.\n");
}

void consumer()
{
    system("rm file");
    printf("File was deleted.\n");
    kill(parent, SIGUSR2); // signal -> file can created by parent
}

int main(void)
{
    system("touch file");

    pid_t pid = fork();

    for(int i = 0; i < 10; ++i)
    {
        if(pid < 0) // error fork()
        {
            perror("fork()");
            return -1;
        }
        else if(pid == 0) // child proces - consumer
        {
                child = getpid();
                signal(SIGUSR1, consumer);
                pause();
        }
        else // parent process - producer
        {
                parent = getpid();
                signal(SIGUSR2, producer);
                // signal -> file can be deleted by child
                kill(child, SIGUSR1); 
        }
    }

    return 0;
}

Edit: I forgot to mention that there can only be one file at a time.

Answer 1

After a lot of research and reading all of the suggestions I finally managed to make the program work. Here is my implementation. If you see any mistakes or perhaps something could have been done better, then feel free to correct my code. I'm open to suggestions.

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

void signal_handler(int signal_number)
{
    sigset_t mask;

    if(sigemptyset(&mask) == -1 || sigfillset(&mask) == -1)
    {// initialize signal set || block all signals
        perror("Failed to initialize the signal mask.");
        return;
    }

    switch(signal_number)
    {
        case SIGUSR1:
        {
            if(sigprocmask(SIG_BLOCK, &mask, NULL) == -1)
            { // entering critical zone
                perror("sigprocmask(1)");
                return;
            } //---------------------

            sleep(1);
            system("rm file");          /* critical zone */
            puts("File was removed.");

              //--------------------
            if(sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
            {// exiting critical zone
                perror("1 : sigprocmask()");
                return;
            }

            break;
        }
        case SIGUSR2:
        {

            if(sigprocmask(SIG_BLOCK, &mask, NULL) == -1)
            {// entering critical zone
                perror("2 : sigprocmask()");
                return;
            } //---------------------

            sleep(1);
            system("touch file");
            puts("File was created.");  /* critical zone */


              // --------------------
            if(sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
            {// exiting critical zone
                perror("sigprocmask(2)");
                return;
            }

            break;
        }
    }
}

int main(void)
{
    pid_t pid = fork();

    struct sigaction sa;
    sa.sa_handler = &signal_handler; // handler function
    sa.sa_flags = SA_RESTART;

    sigaction(SIGUSR1, &sa, NULL);
    sigaction(SIGUSR2, &sa, NULL);

    if(pid < 0)
    {
        perror("fork()");
        return -1;
    }

    for(int i = 0; i < 10; ++i)
    {
        if(pid > 0) // parent - producer
        {
            sleep(2);
            // signal -> file was created
            kill(pid, SIGUSR1);
            pause();
        }
        else // child - consumer
        {
            pause();
            // signal -> file was removed
            kill(getppid(), SIGUSR2);
        }
    }

    return 0;
}