Search code examples
clinuxmultiprocessingfork

What if child process blocked, how to stop parent?

I have to run my processes in strong order, child then parent, what if child gets blocked, how to stop parent?

if ((pid = fork()) == -1) { /* create a child process */
    perror("fork() failed\n");
    exit(1);
}
if (pid == 0) {
    /* child process */
    func1(NULL);

    fflush(stdout);
    return 0;
} else {
    /* parent process */
    wait(NULL);
    func2(NULL);

    fflush(stdout);
}
Solution

  • Aaand as an alternative to an active cpu-busy loop with a timeout doing waitpid() with WNOHANG in a loop, you should prefer to implement it in such a way that cpu is free.

    Do not call wait from parent, instead enable SIGCHLD and setup timeout with a timer and call pause() and wait for and dispatch events from signals with pause(). An example how to do it is even in man 3 wait.

    Also on Linux you can use pidfd_open(pid, 0) and call poll() on it for POLLIN with a timeout.