init improvements

user/init.c

@@ -3,6 +3,8 @@
 
 #define MAX_ARGS 4
 
+static long running = 0;
+
 struct proc {
 	pid_t pid;
 	const char *filename;
@@ -32,44 +34,82 @@ static int spawn(const char *filename, const char **args)
 	exit(1);
 }
 
-int main(void)
+static void spawn_proc(struct proc *proc)
+{
+	int ret;
+
+	// update running on respawn
+	if (proc->pid)
+		running--;
+
+	// attempt to fork / exec
+	ret = spawn(proc->filename, proc->args);
+
+	// handle result
+	if (ret < 0) {
+		printf("init: cannot exec '%s': %d\n", proc->filename, ret);
+		proc->pid = 0;
+	} else {
+		running++;
+		proc->pid = ret;
+	}
+}
+
+static void spawn_proc_loop(struct proc *proc)
+{
+	while (proc->pid == 0)
+		spawn_proc(proc);
+}
+
+static void spawn_all(void)
 {
 	struct proc *proc;
-
-	// spawn our processes
 	for (proc = spawn_table; proc->filename != NULL; proc++) {
-		int pid;
-		pid = spawn(proc->filename, proc->args);
-		if (pid < 0)
-			fprintf(stderr, "init: cannot exec '%s': %d\n", proc->filename,
-					pid);
-		proc->pid = pid;
+		spawn_proc_loop(proc);
 	}
+}
+
+static struct proc *get_proc(pid_t pid)
+{
+	struct proc *proc;
+	for (proc = spawn_table; proc->filename != NULL; proc++) {
+		if (proc->pid == pid)
+			return proc;
+	}
+	return NULL;
+}
+
+int main(void)
+{
+	// spawn our processes
+	spawn_all();
 
 	// clean up dead on restart ours
 	while (1) {
+		struct proc *proc;
 		int pid, status;
 
-		pid = waitpid(0, &status);
-		if (pid < 0)
+		// dont wait if nothing running
+		if (running) {
+			pid = waitpid(0, &status);
+			// ???
+			if (pid < 0)
+				continue;
+		} else {
+			spawn_all();
 			continue;
+		}
 
 		printf("init: pid %d exited with %d\n", pid, status);
 
 		// figure out if this is one of ours
-		for (proc = spawn_table; proc->filename != NULL; proc++) {
-			if (proc->pid == pid) {
-				proc->pid = 0;
-				pid = spawn(proc->filename, proc->args);
-				if (pid < 0)
-					fprintf(stderr, "init: cannot exec '%s': %d\n",
-							proc->filename, pid);
-				proc->pid = pid;
-				break;
-			}
-		}
+		proc = get_proc(pid);
+		if (proc == NULL)
+			continue;
+
+		spawn_proc_loop(proc);
 	}
 
-	// very very bad!
+	// failed to launch anythingvery very bad!
 	return 1;
 }