Two child processes to trigger using epoll and signals - c

Question

process 1 is by timerfd, process 2 is triggered by signal from process1
tc2_main is equal to main
I tried having child1 triggered by timerfd and epoll, child 2 triggered by child 1's epoll and signal, so that child 2 gets triggered every 2 seconds.
but child 2 is never triggered
process timer is wait timer and send signal to child 2
void process_timer(int efd, int timerfd, int pid) {
uint64_t exp;
int ret, nfds;
struct epoll_event event;
for(int i = 0; i < 2; i++){
nfds = epoll_wait(efd, &event, 1, -1);
if (nfds == -1)
handle_error("epoll_wait");
ret = read(timerfd, &exp, sizeof(uint64_t));
if (ret != sizeof(uint64_t))
handle_error("read");
kill(pid, SIGUSR1);
printf("Process %d: Timer expired %lu times\n", getpid(), exp);
fflush(stdout);
}
}
this code is set epoll, timer and signal
and also set child 2
child 2 is wait SIGUSR1 signal
void tc2_main() {
int efd, timerfd;
struct epoll_event event;
struct itimerspec new_value;
cnt = (int*)mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1 ,0);
struct sched_param param;
param.sched_priority = 99;
if (sched_setscheduler(0, SCHED_FIFO, &param) == -1) {
perror("sched_setscheduler");
}
if (efd == -1)
handle_error("epoll_create1");
nice(10);
timerfd = timerfd_create(CLOCK_MONOTONIC, 0);
if (timerfd == -1)
handle_error("timerfd_create");
new_value.it_value.tv_sec = 2;
new_value.it_value.tv_nsec = 0;
new_value.it_interval.tv_sec = 2;
new_value.it_interval.tv_nsec = 0;
sigset_t sigset;
sigemptyset(&sigset);
sigaddset(&sigset, SIGUSR1);
sigprocmask (SIG_BLOCK, &sigset, NULL);
int sfd = signalfd(-1, &sigset, 0);
printf("sigfd : %d\n", sfd);
int ep_sig_fd = epoll_create1(0);
struct epoll_event sig_ev,ev;
sig_ev.data.fd = sfd;
sig_ev.events = EPOLLINT;
if(epoll_ctl(ep_sig_fd, EPOLL_CTL_ADD, sfd, &sig_ev) == -1){
handle_error("epoll_ctl");
}
printf("Child process waiting for signal...\n");
if (timerfd_settime(timerfd, 0, &new_value, NULL) == -1)
handle_error("timerfd_settime");
efd = epoll_create1(0);
if (efd == -1)
handle_error("epoll_create1");
event.data.fd = timerfd;
event.events = EPOLLIN EPOLLET;
if (epoll_ctl(efd, EPOLL_CTL_ADD, timerfd, &event) == -1)
handle_error("epoll_ctl");
pid_t pid = fork();
if (pid == -1)
handle_error("fork");
else if (pid == 0) {
process_timer(efd, timerfd, getppid());
(*cnt)++;
exit(EXIT_SUCCESS);
} else {
pid_t pid2 = fork();
fflush(stdout);
if(pid2 == -1) {
handle_error("fork");
} else if(pid2 == 0) {
struct signalfd_siginfo siginfo;
printf("Child 2: waiting for signal...\n");
int s = epoll_wait(ep_sig_fd, &sig_ev, 1, -1);
printf("aaa\n");
fflush(stdout);
if(s < 0) handle_error("epoll wait");
if (read(sfd, &siginfo, sizeof(siginfo)) != sizeof(siginfo)) {
perror("read");
exit(EXIT_FAILURE);
}
} else {
wait(NULL);
}
}
exit(EXIT_SUCCESS);
}