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



// pro zapamatovani, jestli signal prisel nebo ne...
volatile sig_atomic_t usr_interrupt = 0;

void synch_signal(int sig) {
	usr_interrupt = 1;
}

void child_function(int stav) {
	sigset_t mask;
	sigemptyset(&mask);
	sigaddset(&mask,SIGUSR1);


	printf("potomek\n");
	kill(getppid(),SIGUSR1);
	printf("po signalu\n");
	sigsuspend(&mask);
	printf("po zotavenis\n");
	exit(EXIT_SUCCESS);
}


int main(void) {
	struct sigaction usr_action;
	sigset_t block_mask, old_mask;
	int stav;

	sigfillset(&block_mask);	
	usr_action.sa_handler = synch_signal;
	usr_action.sa_mask = block_mask;
	usr_action.sa_flags = 0;
	sigaction (SIGUSR1, &usr_action, NULL);

	stav = fork();
	if(stav == 0) child_function(2);

	sigemptyset(&block_mask);
	sigaddset(&block_mask,SIGUSR1);
	sigprocmask(SIG_BLOCK, &block_mask, &old_mask);
	printf("cekam\n");
	
	while(!usr_interrupt) {
		sigsuspend(&old_mask);
	}
	printf("docekal sem\n");
	sigprocmask(SIG_UNBLOCK, &block_mask, NULL);
	
	kill(stav,SIGUSR1);

	return(EXIT_SUCCESS);

}