Why Don't The Children Recive The Signal - c

Question

I have a parent process that is spawning X number of child processes (player) based off the first argument passed to the program. After each child is spawned it sends them a signal. For now all I want the children to do it print they received the signal and exit, but they don't seem to get the signal from the parent. Are the children not getting the signal or am I handling it wrong?
Parent:
#define _POSIX_SOURCE
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
void reciveCard() {
write(1, "signal recived\n", 15);
exit(0);
}
int main(int argc, char **argv) {
int numPlayers, i;
int *kpids;
numPlayers = atoi(argv[1]);
kpids = malloc(numPlayers * sizeof(int));
signal(SIGUSR1, SIG_IGN);
for(i = 0; i < numPlayers; i++) {
if((kpids[i] = fork()) == 0) {
if(execlp("./player\0", "./player\0", (char *) NULL) == -1) {
printf("error\n");
exit(1);
}
}
}
for(i = 0; i < numPlayers; i++) {
printf("%d\n", kpids[i]);
kill(kpids[i], SIGUSR1);
}
wait(NULL);
return 0;
}
Child:
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
void reciveCard() {
write(1, "signal recived\n", 15);
exit(0);
}
int main() {
signal(SIGUSR1, reciveCard);
while(1) {
sleep(1);
}
return 0;
}

Answer 1

You have a race condition.
The parent program does the fork calls so fast that it falls into the kill loop before any child has a chance to do the execlp.
Thus, the child can't set up the handler fast enough. That is, when the signal comes in, the child is still ignoring it because of the parent's SIG_IGN call that it has inherited.
Now, after the execlp, the child will set up the handler, but the signal has already occurred, so the the handler will never be called.
To see this, add a sleep(1) between the two parent loops and it should work.