How to use sigsuspend with virtual timer - c

Question

I want to use a virtual timer to pause a while loop till the timer expires. The goal is to have a function run periodically given a time interval.
I read on the gnu.org site that using pause() can be troublesome and they suggest using sigsuspend instead. I am using the code given in the example. My program looks as follows.
void handler_SIGALRM(int signo)
{
signo = 0; /* Get rid of warning "unused parameter ‘signo’" (in a portable way). */
puts(" ***********Cleared Alarm");
return;
}
int main(int argc, char *argv[]) {
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = handler_SIGALRM;
if (-1 == sigaction(SIGALRM, &sa, NULL ))
{
perror("sigaction() failed");
exit(EXIT_FAILURE);
}
struct itimerval it_val; /* for setting itimer */
it_val.it_value.tv_sec = 3; // INTERVAL/1000;
it_val.it_value.tv_usec = 0;//simData.misc
it_val.it_interval = it_val.it_value;
if (setitimer(ITIMER_REAL, &it_val, NULL) == -1) {
perror("error calling setitimer()");
exit(1);
}
sigset_t mask, oldmask;
sigemptyset(&mask);
sigaddset(&mask,SIGALRM);
/* Wait for a signal to arrive. */
sigprocmask(SIG_BLOCK, &mask, &oldmask);
sigsuspend(&oldmask);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
puts("unblocked");
sigprocmask(SIG_BLOCK, &mask, &oldmask);
while(1)
{
//...
sigsuspend(&oldmask);
//...
}
sigprocmask(SIG_UNBLOCK, &mask, NULL);
return 0;
}
The code above accomplishes the "pause" that I need. However, when I run it embedded in another program (threaded). It just hangs, and just keeps calling _handler_SIGALRM_.
Am I doing something wrong? Why could my program be hanging?