signalfd-with-threads-sucks.c

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <pthread.h>
#include <sys/signalfd.h>
#include <sys/time.h>
#include <sys/types.h>

#define handle_error(msg) \
    do { perror(msg); exit(EXIT_FAILURE); } while (0)
void chld_handler(int signum) {
    pthread_t id = pthread_self();
    printf("GOT SIGNAL %d in THREAD %li. This should not happen !\n", signum, (long int) id);
}
void* my_thread(void *args) {
    pthread_t id = pthread_self();

    sigset_t mask;
    sigemptyset(&mask);
    sigaddset(&mask, SIGCHLD);
    if (pthread_sigmask(SIG_BLOCK, &mask, NULL) == -1)
        handle_error("sigprocmask in thread");

    for (;;) {
        sleep(1);
        printf("looping in %li.\n", (long int) id);
    }
}
void setup_thread() {
    pthread_t id;
    int err = pthread_create(&id, NULL, &my_thread, NULL);
    if (err) {
        printf("can't create thread, error: %d\n", err);
    } else {
        printf("thread created successfully.\n");
    }
}
int main(int argc, char *argv[]) {
    struct sigaction action = {.sa_handler = chld_handler, .sa_flags = 0};
    sigemptyset (&action.sa_mask);
    sigaction(SIGCHLD, &action, NULL);

    int fd;
    struct signalfd_siginfo si;
    ssize_t s;

    sigset_t mask;
    sigemptyset(&mask);
    sigaddset(&mask, SIGCHLD);
    if (pthread_sigmask(SIG_BLOCK, &mask, NULL) == -1)
        handle_error("sigprocmask");

    fd = signalfd(-1, &mask, SFD_NONBLOCK|SFD_CLOEXEC);
    if (fd == -1)
        handle_error("signalfd");

    setup_thread();

    for (;;) {
        int pid = fork();
        printf("Forked %d\n", pid);
        if (pid) {
            struct timeval tv = {.tv_sec = 1, .tv_usec = 0};
            fd_set readfds;

            FD_ZERO(&readfds);
            FD_SET(fd, &readfds);

            // don't care about writefds and exceptfds:
            select(fd+1, &readfds, NULL, NULL, &tv);
            if (FD_ISSET(fd, &readfds)) {
                s = read(fd, &si, sizeof(struct signalfd_siginfo));
                if (s != sizeof(struct signalfd_siginfo))
                    handle_error("read");

                printf("Got signal %d (%d)\n", si.ssi_signo, si.ssi_pid);
            }
        } else {
            sleep(2);
            exit(0);
        }
    }
}

I appreciate you helping my OS assignment. This is only one which I found that implements signalfd() in thread. I love you.