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

void die(const char* msg)
{
	fprintf(stderr, "ERR!! %s: %s\n", msg, strerror(errno));
	exit(-1);
}

char thread_stack[4096];

int thread_func(void *arg)
{
	execl("/bin/true", NULL);
	die("exec");
	return 0;
}

void proc_func(void)
{
	int pid;

	for (;;)
		if ((pid = fork())) {
			if (pid != waitpid(pid, NULL, 0))
				die("wait4");
		} else {
			struct sigevent sigev = {};
			struct itimerspec itsp = {};
			timer_t tid;

			sigev.sigev_signo = SIGRTMIN;
			sigev.sigev_notify = SIGEV_SIGNAL;
			if (timer_create(CLOCK_MONOTONIC, &sigev, &tid) == -1)
				die("timer_create");

			itsp.it_value.    tv_nsec = 1;
			itsp.it_interval. tv_nsec = 1;
			if (timer_settime(tid, 0, &itsp, NULL))
				die("timer_settime");

			if (clone(thread_func, thread_stack + 2048,
					CLONE_THREAD|CLONE_SIGHAND|CLONE_VM|CLONE_FILES,
					NULL) < 0)
				die("clone");

			pause();
		}
}

int main(void)
{
	int pn;

	signal(SIGRTMIN, SIG_IGN);

	for (pn = 0; pn < 16; ++pn)
		if (!fork())
			proc_func();

	pause();

	return 0;
}