/* Signals handling.. */
#include <signal.h>
+#include <sys/shm.h>
+#include <sys/msg.h>
+
+
/** If buffer is too small to hold entire string, it is incremented by this value */
#define BUFFER_STEP 16
/** File descriptor of pipe */
int file_descriptor;
+
+/**
+ * Shared memory variables
+ */
+/**
+ * Memory key for processes. Must be same between all processes to properly
+ * communicate.
+ */
+key_t shmkey = 18912;
+/**
+ * Id of the shared memory
+ */
+int shmid;
+
+/**
+ * Message shared by processes. Contains array of process IDs
+ */
+struct message {
+ pid_t pids[3];
+};
+
+struct message * processes = NULL;
+
+/**
+ * Message Queue variables
+ */
+
+/**
+ * Unique key of message queue.
+ */
+key_t qkey = 12356;
+
+/**
+ * Queue descriptor.
+ */
+int qid;
+
+/**
+ * Structure holding queue message data.
+ * Parameter mtype describes process to whom message is sent.
+ * Parameter signo is a signal to raise after getting message.
+ */
+struct queue_message {
+ long mtype;
+ int signo[1];
+};
+
+void notify_other_processes(int signo) {
+ int i = 0;
+ struct queue_message msg;
+ msg.signo[0] = signo;
+
+ for (; i < 3; i++) {
+ pid_t pid = processes->pids[i];
+ // Bleh
+ if (i != 0 && pid != 0) {
+ msg.mtype = i+1;
+ fprintf(stderr, "[%s] Sending message of type (%d) with value %d\n", "process1", msg.mtype, msg.signo[0]);
+ msgsnd(qid, &msg, sizeof(int), 0);
+ fprintf(stderr, "[%s] Sending signal %s (%d) to PID: %d\n", "process1", strsignal(SIGUSR1), SIGUSR1, pid);
+ kill(pid, SIGUSR1);
+ }
+ }
+}
+
/**
* Handler for signals.
*/
{
fprintf(stderr, "[%s] Received %s!\n", "process1", strsignal(signo));
if (signo == SIGUSR1) {
+ fprintf(stderr, "[%s] > Notified!\n", "process1");
+ struct queue_message msg;
+ /* Check queues from both other processes */
+ if (msgrcv(qid, &msg, sizeof(int), 1, 0) > 0) {
+ fprintf(stderr, "[%s] > Notified with value: %s!\n", "process1", strsignal(msg.signo[0]));
+ raise(msg.signo[0]);
+ }
}
else if (signo == SIGTERM) {
+ fprintf(stderr, "[%s] > Signalling other processes..\n", "process1");
+ processes->pids[0] = 0;
+ notify_other_processes(signo);
+
fprintf(stderr, "[%s] > Releasing resources\n", "process1");
close(write_pipe);
unlink(write_pipe);
exit(0);
}
else if (signo == SIGTSTP) {
+ fprintf(stderr, "[%s] > Signalling other processes..\n", "process1");
+ processes->pids[0] = 0;
+ notify_other_processes(signo);
+// sleep(1);
+ processes->pids[0] = getpid();
+
fprintf(stderr, "[%s] > Closing pipe\n", "process1");
close(write_pipe);
+ raise (SIGSTOP);
}
else if (signo == SIGCONT) {
fprintf(stderr, "[%s] > Opening pipe\n", "process1");
file_descriptor = open(write_pipe, O_WRONLY);
+ processes->pids[0] = 0;
+ notify_other_processes(signo);
+// sleep(1);
+ processes->pids[0] = getpid();
}
}
fprintf(stderr, "can't catch SIGCONT\n");
}
+ /*
+ * Register memory to share with other processes, and pass current
+ * process id to the array.
+ */
+ shmid = shmget(shmkey, sizeof(struct message), IPC_CREAT | 0666);
+
+ processes = (struct message *)shmat(shmid, NULL, 0);
+ processes->pids[0] = getpid();
+
+ fprintf(stderr, "[%s] Shared pid: %d\n", "process1", getpid());
+
+ /**
+ * Register message queue to communicate with other processes
+ */
+ qid = msgget(qkey, IPC_CREAT | 0666);
+
mkfifo(write_pipe, 0666);
file_descriptor = open(write_pipe, O_WRONLY);