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#include "csapp.h"
static void signal_handler(int signum, siginfo_t *info, void *data) {
if (signum == SIGINT) {
safe_printf("(%d) Screw you guys... I'm going home!\n", getpid());
_exit(0);
}
}
static void play(pid_t next, const sigset_t *set) {
for (;;) {
printf("(%d) Waiting for a ball!\n", getpid());
/* TODO: Something is missing here! */
sigset_t mask;
sigfillset(&mask);
sigdelset(&mask, SIGUSR1);
sigdelset(&mask, SIGINT);
Sigsuspend(&mask);
usleep((300 + random() % 400) * 1000);
Kill(next, SIGUSR1);
printf("(%d) Passing ball to (%d)!\n", getpid(), next);
}
}
int main(int argc, char *argv[]) {
if (argc != 2)
app_error("Usage: %s [CHILDREN]", argv[0]);
int children = atoi(argv[1]);
if (children < 4 || children > 20)
app_error("Give number of children in range from 4 to 20!");
/* Register signal handler for SIGUSR1 */
struct sigaction action = {.sa_sigaction = signal_handler};
Sigaction(SIGINT, &action, NULL);
Sigaction(SIGUSR1, &action, NULL);
/* TODO: Start all processes and make them wait for the ball! */
sigset_t mask;
sigfillset(&mask);
sigprocmask(SIG_BLOCK, &mask, NULL);
pid_t prev_pid = getpid();
for (int i = 1; i <= children; i++) {
int pid = Fork();
if (pid == 0) {
play(prev_pid, NULL);
}
prev_pid = pid;
}
Kill(prev_pid, SIGUSR1);
play(prev_pid, NULL);
return EXIT_SUCCESS;
}
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