spurious-mach-sigwait.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <pthread.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>

static volatile int nsignals, nerrors;
static void *signal_listener(void *arg)
{
    sigset_t sset;
    while (1) {
        int sig = SIGALRM;
        sigemptyset(&sset);
        sigaddset(&sset, SIGHUP);
        sigaddset(&sset, SIGINT);
        sigaddset(&sset, SIGINFO);
        errno = 0;
        if (sigwait(&sset, &sig))
            abort();
        if (errno)
            nerrors++;
        else
            printf("got %d, errno %d\n", sig, errno);
        nsignals++;
    }
}

static void sigchld(int sig, struct __siginfo *siginfo, void *dummy) { }
static void sigalrm(int sig, struct __siginfo *siginfo, void *dummy) { }
int main(int argc, char **argv)
{
    pthread_t signals_thread;
    struct sigaction act;
    memset(&act, 0, sizeof(struct sigaction));
    sigemptyset(&act.sa_mask);
    act.sa_sigaction = sigchld;
    if (sigaction(SIGCHLD, &act, NULL) < 0)
        abort();
    act.sa_sigaction = sigalrm;
    if (sigaction(SIGALRM, &act, NULL) < 0)
        abort();
    if (pthread_create(&signals_thread, NULL, signal_listener, NULL) != 0)
        abort();
    struct itimerval tm;
    tm.it_value.tv_sec = 0;
    tm.it_value.tv_usec = 25;
    tm.it_interval.tv_sec = 0;
    tm.it_interval.tv_usec = 25;
    setitimer(ITIMER_REAL, &tm, NULL);
    puts("start.\n");
    int i;
    sigset_t sset, oset;
    sigfillset(&sset);
    for (i = 0; i < 1024; i++) {
        sigprocmask(SIG_SETMASK, &sset, &oset);
        usleep(1000);
        sigprocmask(SIG_SETMASK, &oset, NULL);
    }
    puts("done.\n");
    printf("wakeups: %d\nerrors: %d\n", nsignals, nerrors);
    return 0;
}